U.S. patent application number 11/120243 was filed with the patent office on 2005-11-03 for self-activating downhole tool.
This patent application is currently assigned to Halliburton Energy Services, Inc.. Invention is credited to Burris, Wesley J. II, Fripp, Michael L., Goiffon, John J., Hales, John H., Rodgers, John, Schwendemann, Kenneth L., Starr, Phillip M., Towers, Darrin N..
Application Number | 20050241835 11/120243 |
Document ID | / |
Family ID | 35185905 |
Filed Date | 2005-11-03 |
United States Patent
Application |
20050241835 |
Kind Code |
A1 |
Burris, Wesley J. II ; et
al. |
November 3, 2005 |
Self-activating downhole tool
Abstract
An autonomous downhole tool for use in a well bore is moved
along at least a partial length of the well bore via an external
force, and the tool is self-operable to perform one or more
functions at one or more locations within the well bore.. A method
for operating a downhole tool within a well bore comprises
deploying the tool along at least a partial length of the well bore
via an external force, and self-activating one or more functions of
the tool, wherein the tool does not receive command communications
from the surface.
Inventors: |
Burris, Wesley J. II;
(Flower Mound, TX) ; Schwendemann, Kenneth L.;
(Flower Mound, TX) ; Starr, Phillip M.; (Duncan,
OK) ; Fripp, Michael L.; (Carrollton, TX) ;
Goiffon, John J.; (Dallas, TX) ; Hales, John H.;
(Frisco, TX) ; Rodgers, John; (Trophy Club,
TX) ; Towers, Darrin N.; (Carrollton, TX) |
Correspondence
Address: |
JOHN W. WUSTENBERG
P.O. BOX 1431
DUNCAN
OK
73536
US
|
Assignee: |
Halliburton Energy Services,
Inc.
Houston
TX
|
Family ID: |
35185905 |
Appl. No.: |
11/120243 |
Filed: |
May 2, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60567743 |
May 3, 2004 |
|
|
|
Current U.S.
Class: |
166/381 ;
166/313; 166/53 |
Current CPC
Class: |
E21B 23/00 20130101;
E21B 47/04 20130101; E21B 43/119 20130101; E21B 23/10 20130101 |
Class at
Publication: |
166/381 ;
166/053; 166/313 |
International
Class: |
E21B 043/00 |
Claims
What is claimed is:
1. An autonomous downhole tool for use in a well bore wherein the
tool is moved along at least a partial length of the well bore via
an external force.
2. The autonomous downhole tool of claim 1 wherein the autonomous
tool is self-operable to perform one or more functions at one or
more locations within the well bore.
3. The autonomous downhole tool of claim 2 wherein the autonomous
tool is a plug self-operable to set at more than one location
within the well bore.
4. The autonomous downhole tool of claim 2 wherein the autonomous
tool is a perforating gun self-operable to fire at more than one
location within the well bore.
5. The autonomous downhole tool of claim 1, further including: an
activator operable to self-activate one or more functional
components of the tool within the well bore without receiving
command communications from the surface.
6. The autonomous downhole tool of claim 5 wherein the one or more
functional component provides one or more functions comprising:
slowing the tool, stopping the tool, holding the tool in the well
bore, perforating a well bore casing, evaluating the formation,
evaluating a well bore assembly, isolating a well bore segment,
releasing the tool in the well bore, releasing a component of the
tool, or a combination thereof.
7. The autonomous downhole tool of claim 5 wherein one of the
functional components comprises a brake.
8. The autonomous downhole tool of claim 7 wherein the brake
comprises a fluid drag component, a pressure differential
component, an eddy current component, a generator component, a
rotary component, a mechanical component, a magnetic component, an
adhesive component, a suction component, an inflatable component, a
variable buoyancy component, or a combination thereof.
9. The autonomous downhole tool of claim 5, further comprising an
onboard navigation system operable to estimate a location of the
autonomous tool within the well bore.
10. The autonomous downhole tool of claim 10 wherein the tool
self-activates the one or more functional components of the tool
based on the estimation of the location of the autonomous tool.
11. A method for operating a downhole tool within a well bore
comprising: deploying the tool along at least a partial length of
the well bore via an external force; and self-activating one or
more functions of the tool; wherein the tool does not receive
command communications from the surface.
12. The method of claim 11 further comprising initializing the
downhole tool.
13. The method of claim 12 wherein initializing the tool comprises
providing a well bore log to the tool.
14. The method of claim 12 wherein initializing the tool comprises
providing a well bore log and a mission program to the tool.
15. The method of claim 14 wherein self-activating one or more
functions of the tool comprises following the mission program.
16. The method of claim 11 further comprising self-determining the
location of the tool by sensing two or more parameters in the well
bore via the tool and determining the location of the tool based on
the sensed parameters.
17. The method of claim 16 further comprising determining a
velocity of the tool based on the sensed parameters.
18. The method of claim 11 further comprising returning the tool or
a component thereof to the surface.
19. The method of claim 18 wherein the returning the tool or a
component thereof to the surface is accomplished without mechanical
linkage with the surface.
20. The method of claim 11 further comprising self-deactivating the
one or more functions of the tool.
21. The method of claim 11 wherein the self-activating one or more
functions of the tool is performed at one or more locations within
the well bore.
22. The method of claim 11 wherein self-activating one or more
functions of the tool comprises sealing the well bore with the
tool.
23. The method of claim 11 wherein self-activating one or more
functions of the tool comprises perforating a casing in the well
bore.
24. A downhole tool for use in a well bore comprising: an activator
operable to self-activate one or more functional components of the
tool within a well bore; wherein the tool is moved along at least a
partial length of the well bore via an external force; and wherein
the tool does not receive command communications from the
surface.
25. The downhole tool of claim 24 wherein the tool comprises a frac
plug, a bridge plug, a packer, a logging tool, a casing patch, a
formation tester, a perforating gun, a whipstock, a marker setting
tool, a tool servicing device, or a combination thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit under 35 U.S.C.
.sctn. 119(e) of U.S. Provisional Application Ser. No. 60/567,743
filed May 3, 2004 and entitled "Autonomous Navigation for a
Downhole Tool," by Wesley Jay Burris II, et al, which is
incorporated herein by reference for all purposes.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
REFERENCE TO A MICROFICHE APPENDIX
[0003] Not applicable.
FIELD OF THE INVENTION
[0004] The present application relates to autonomous downhole tools
that are moved in a well bore via an external force, and methods of
servicing a well bore using such tools. The present application
also relates to autonomous downhole tools that are self-navigating
without receiving location communications from an external source,
such as from the surface or another downhole component. The present
application further relates to autonomous downhole tools that are
self-activating without receiving command communications from an
external source.
BACKGROUND OF THE INVENTION
[0005] A wide variety of downhole tools may be used within a well
bore in connection with producing hydrocarbons from a hydrocarbon
formation. Downhole tools such as frac plugs, bridge plugs, and
packers, for example, may be used to seal a component against
casing along the well bore wall or to isolate one pressure zone of
the formation from another. In addition, perforating guns may be
used to create perforations through casing and into the formation
to produce hydrocarbons.
[0006] Downhole tools are typically conveyed into the well bore on
a wireline, tubing, pipe, or another type of cable. In conventional
systems, the operator estimates the location of the downhole tool
based on this mechanical connection and also communicates with the
tool through this mechanical connection. For example, the operator
may send communications to the downhole tool via the cable to
command the setting of a plug in the well bore, or to command the
firing of a perforating gun. This mechanical connection may be
subject to various problems including time consuming and costly
operations, increased safety concerns, more personnel on site, and
risk for breakage of the connection.
[0007] Therefore, a need exists for downhole tools that may be
lowered, pumped, or released into the well bore, and that are
operable to self-determine their location within the well bore
without receiving location communications from the surface.
Further, a need exists for downhole tools that are operable to
self-activate without receiving command communications from the
surface.
SUMMARY OF THE INVENTION
[0008] Disclosed herein is an autonomous downhole tool for use in a
well bore wherein the tool is moved along at least a partial length
of the well bore via an external force. In an embodiment, the
autonomous tool is self-operable to perform one or more functions
at one or more locations within the well bore. In various
embodiments, the autonomous tool is a plug self-operable to set at
more than one location within the well bore, or a perforating gun
self-operable to fire at more than one location within the well
bore.
[0009] In an embodiment, the autonomous downhole tool further
comprises an activator operable to self-activate one or more
functional components of the tool within the well bore without
receiving command communications from the surface. In an
embodiment, the one or more functional component provides one or
more functions comprising: slowing the tool, stopping the tool,
holding the tool in the well bore, perforating a well bore casing,
evaluating the formation, evaluating a well bore assembly,
isolating a well bore segment, releasing the tool in the well bore,
releasing a component of the tool, or a combination thereof. In an
embodiment, one of the functional components comprises a brake. In
various embodiments, the brake comprises a fluid drag component, a
pressure differential component, an eddy current component, a
generator component, a rotary component, a mechanical component, a
magnetic component, an adhesive component, a suction component, an
inflatable component, a variable buoyancy component, or a
combination thereof.
[0010] In an embodiment, the autonomous downhole tool further
comprises an onboard navigation system operable to estimate a
location of the autonomous tool within the well bore, and the tool
self-activates the one or more functional components of the tool
based on the estimation of the location of the autonomous tool.
[0011] Further disclosed herein is a method for operating a
downhole tool within a well bore comprising deploying the tool
along at least a partial length of the well bore via an external
force, and self-activating one or more functions of the tool,
wherein the tool does not receive command communications from the
surface. In an embodiment, the method further comprises
initializing the downhole tool. In various embodiments,
initializing the tool comprises providing a well bore log to the
tool, or providing a well bore log and a mission program to the
tool. In an embodiment, self-activating one or more functions of
the tool comprises following the mission program.
[0012] In an embodiment, the method further comprises
self-determining the location of the tool by sensing two or more
parameters in the well bore via the tool and determining the
location of the tool based on the sensed parameters. In an
embodiment, the method further comprises determining a velocity of
the tool based on the sensed parameters.
[0013] The method may further comprise returning the tool or a
component thereof to the surface. In an embodiment, returning the
tool or a component thereof to the surface is accomplished without
mechanical linkage with the surface. In various embodiments, the
method further comprises self-deactivating the one or more
functions of the tool, or self-activating one or more functions of
the tool at one or more locations within the well bore. In various
embodiments, self-activating one or more functions of the tool
comprises sealing the well bore with the tool, or perforating a
casing in the well bore.
[0014] Further disclosed herein is a downhole tool for use in a
well bore comprising an activator operable to self-activate one or
more functional components of the tool within a well bore, wherein
the tool is moved along at least a partial length of the well bore
via an external force, and wherein the tool does not receive
command communications from the surface. In various embodiments,
the downhole tool comprises a frac plug, a bridge plug, a packer, a
logging tool, a casing patch, a formation tester, a perforating
gun, a whipstock, a marker setting tool, a tool servicing device,
or a combination thereof.
[0015] These and other features and advantages will be more clearly
understood from the following detailed description taken in
conjunction with the accompanying drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] For a more complete understanding of the present disclosure
and the advantages thereof, reference is now made to the following
brief description of the figures, taken in connection with the
accompanying drawings showing various exemplary embodiments and the
detailed description, wherein like reference numerals represent
like parts.
[0017] FIG. 1 is a schematic, cross-sectional view of an operating
environment depicting an autonomous downhole tool being lowered
into a well bore extending into a subterranean hydrocarbon
formation;
[0018] FIG. 2 is a schematic, cross-sectional side view of another
operating environment depicting an autonomous downhole tool being
pumped into the well bore;
[0019] FIG. 3 is a schematic, cross-sectional side view of another
operating environment depicting an autonomous downhole tool
traversing the well bore by force of gravity;
[0020] FIG. 4 is a schematic representation of an autonomous
downhole tool;
[0021] FIG. 5 is a block diagram of a downhole tool comprising a
navigation system and at least one functional component;
[0022] FIG. 6 depicts a casing string indicating absolute location,
a first location estimate, and a second location estimate at
several points along the casing string;
[0023] FIG. 7 is a flow chart for performing a method of
self-location;
[0024] FIG. 8 is a flow chart for performing another method of
self-location;
[0025] FIG. 9 is an enlarged cross-sectional side view of an
embodiment of an autonomous downhole tool comprising a frac plug in
a run-in position;
[0026] FIG. 10 is an enlarged cross-sectional side view of the
autonomous frac plug of FIG. 9 in a set position wherein fluid is
prevented from flowing downwardly through the frac plug;
[0027] FIG. 11 is an enlarged cross-sectional side view of the
autonomous frac plug of FIG. 9 in the set position wherein fluid is
permitted to flow upwardly through the frac plug;
[0028] FIG. 12 is an enlarged cross-sectional side view of the
autonomous frac plug of FIG. 9 in a flow-back position to return
the autonomous frac plug to the surface;
[0029] FIG. 13 is a cross-sectional view of four stages of a method
for performing a fracturing well service job using autonomous
downhole tools;
[0030] FIG. 14 is a cross-sectional view of a frac plug and a
perforating gun disposed between each production zone in a
hydrocarbon formation;
[0031] FIG. 15 is a cross-sectional view of three stages of a
method for perforating a casing using more than one autonomous
perforating gun; and
[0032] FIG. 16 is a cross-sectional view of three stages of a
method for perforating a casing using an autonomous downhole tool
comprising a plurality of perforating guns.
DETAILED DESCRIPTION
[0033] The present application relates to autonomous downhole tools
that are moved at least a partial length along a well bore via an
external force. In an embodiment, the autonomous downhole tool is
moved along substantially the entire length of the well bore via an
external force. In various embodiments, the external force is
provided by a cable, by hydraulic pressure, by force of gravity, or
by a combination thereof. In an embodiment, the autonomous downhole
tool is not self-transportable via an onboard power supply. In an
embodiment, the autonomous downhole tool is non-robotic. In an
embodiment, the autonomous downhole tool does not provide its own
locomotion. In an embodiment, the autonomous downhole tool is not
self-propelling. In an embodiment, the autonomous downhole tool
does not move within the well bore under its own power. In an
embodiment, the autonomous downhole tool does not move within the
well bore via traction with the well bore wall. In an embodiment,
the autonomous downhole tool does not comprise an operable
propeller, wheels or tracks for self-propulsion along the well
bore.
[0034] In an embodiment, such autonomous downhole tools are
self-navigating such that the tool is operable to self-determine
its location as it traverses the well bore without receiving
location communications from an external source, such as from the
surface or another downhole component. In another embodiment, such
autonomous downhole tools are self-activating such that the tool is
operable to self-activate one or more functions of the tool at one
or more locations within the well bore without receiving command
communications from an external source.
[0035] FIG. 1, FIG. 2, and FIG. 3 each schematically depict various
operating environments for an autonomous downhole tool 100 for use
in a well bore 120 wherein the autonomous downhole tool 100 is
moved along at least a partial length of the well bore 120 via an
external force.
[0036] Referring to FIG. 1, in a first operating environment, a
cable 118 provides the external force for moving the autonomous
downhole tool 100 within the well bore 120. In more detail, a
drilling rig 110 is positioned on the earth's surface 105 and
extends over and around a well bore 120 that penetrates a
subterranean formation F for the purpose of recovering
hydrocarbons. At least the upper portion of the well bore 120 may
be lined with casing 125 that is cemented 127 into position against
the formation F in a conventional manner. In embodiments, at least
some portions of the well bore 120 may be open hole with no casing
125 installed therein. The drilling rig 110 may include a derrick
112 with a rig floor 114 through which a cable 118, such as a
wireline, a slick line, a coiled tubing, or a pipe string, for
example, extends downwardly from the drilling rig 110 into the well
bore 120. The cable 118 supports and lowers the autonomous downhole
tool 100 into the well bore 120 to perform one or more functions.
The drilling rig 110 is conventional and therefore includes a motor
driven winch or other conveyance and associated equipment for
extending the cable 118 into the well bore 120. While the exemplary
operating environment depicted in FIG. 1 refers to a stationary
drilling rig 110 for lowering the autonomous downhole tool 100
within the well bore 120, one of ordinary skill in the art will
readily appreciate that mobile workover rigs, well servicing units,
coiled tubing units, and the like, could also be used to lower the
tool 100 into the well bore 120.
[0037] In an embodiment, the autonomous downhole tool 100 is
self-navigating. Namely, the downhole tool 100 is operable to
self-determine its location within the well bore 120 as the tool
100 is being lowered by the cable 118. Therefore, the tool 100 does
not require location communications from the surface 105 via the
cable 118, for example, to determine its location as in
conventional systems. As a result, the cable 118 may be deployed at
a faster rate. In an embodiment, the autonomous downhole tool 100
is operable to activate one or more functions of the tool 100 at
one or more sensed locations in response to command communications
received from an external source, such as from the surface 105 via
the cable 118 or via wireless communications, for example, or from
another downhole component 150.
[0038] In another embodiment, the downhole tool 100 is
self-activating. Namely, the tool 100 is operable to self-activate
one or more functions of the tool 100 at sensed locations within
the well bore 120 without receiving command communications from an
external source.
[0039] Referring now to FIG. 2, in a second operating environment,
the autonomous downhole tool 100 may be launched into the well bore
120 via a lubricator (not shown) or simply dropped into the well
bore 120. Then hydraulic pressure provides the external force for
moving the tool 100 along at least a partial length of the well
bore 120. In particular, the autonomous downhole tool 100 comprises
an optional wiper 130 that engages and seals against the casing 125
within the well bore 120. A fluid is pumped into the well bore 120,
as represented by the flow arrows 135, to force the tool 100 to
descend rather than lowering the tool 100 by a cable 118 from the
surface 105.
[0040] Referring now to FIG. 3, in a third operating environment,
the autonomous downhole tool 100 may be launched into the well bore
120 via a lubricator (not shown) or simply dropped into the well
bore 120. Then gravity provides the external force for moving the
tool 100 along at least a partial length of the well bore 120. In
particular, the autonomous downhole tool 100 does not seal against
the casing 125. Rather, the tool 100 is simply released into the
well bore 120 and descends by free-falling via the force of
gravity, as represented by the gravity vector 140, instead of being
lowered by a cable 118 from the surface 105, or being pumped down
the well bore 120 by a fluid 135.
[0041] Although the operating environments of FIG. 1, FIG. 2, and
FIG. 3 each depict a single type of external force, as one of
ordinary skill in the art will appreciate, the autonomous downhole
tool 120 may be moved at least a partial distance along the well
bore 120 using a combination of external forces. For example, in
another operating environment, the autonomous downhole tool 100 may
be conveyed by a cable 118 along a partial length of the well bore
120, then released from the cable 118 and moved along the well bore
120 via hydraulic pressure, force of gravity, or both. In another
operating environment, the autonomous downhole tool 100 may be
pumped along a partial length of the well bore 120, and then
free-fall via gravity along the well bore 120, or vice versa.
[0042] Further, the autonomous downhole tool 100 may be moved along
the well bore 120 using a combination of external forces and
self-locomotion. For example, the autonomous downhole tool 100 may
be moved along at least a partial length of the well bore 120 via
an external force, such as a cable 118 that does not provide
location or command communications to the tool 100, gravity,
hydraulic pressure, or a combination thereof, then self-propelled
along another length of the well bore 120 using a propeller or
tracks that frictionally engage the casing 125.
[0043] The autonomous downhole tool 100 may comprise a variety of
different forms. By way of example, in an embodiment, the
autonomous downhole tool 100 comprises a well bore zonal isolation
device, such as a frac plug, a bridge plug, or a packer. A well
bore zonal isolation device functions to separate any two areas
within a well bore 120. More specifically, such devices separate
the area in the well bore 120 above the device from the area of the
well bore 120 below the device. In various other embodiments, the
autonomous downhole tool 100 comprises a filter, a sand screen, a
logging tool, a casing patch, a formation tester, a perforating
gun, a whipstock, a marker setting tool, a servicing device for a
downhole component, or any other temporary or permanent downhole
tool.
[0044] In an embodiment, the autonomous downhole tool 100 is a well
bore zonal isolation device or a perforating gun that is moveable
along at least a partial length the well bore 120 via an external
force and has a communication line connected thereto from the
surface 105. The communication line is operable to provide
communications to and from the zonal isolation device or the
perforating gun in the well bore 120. In an embodiment, the
communication line is non-supportive of the device or the
perforating gun in the well bore, in contrast to the cable 118
described herein, which has the ability to support the entire tool
100 as it is conveyed into or retrieved from the well bore 120.
[0045] The autonomous downhole tool 100 may in various embodiments
comprise a variety of different components and functionalities.
FIG. 4 schematically depicts an autonomous downhole tool 755
comprising one or more of the numbered components. In an
embodiment, the autonomous downhole tool 755 comprises a navigation
system 756. In an embodiment, the autonomous downhole tool 755
comprises one or more functional components 763, which may include
a braking system 760. In an embodiment, the autonomous downhole
tool 755 comprises one or more activators 790 operable to activate
the one or more functional components 763 of the tool 755,
including the braking system 760. In an embodiment, the autonomous
downhole tool 755 comprises a detachable component 800. In an
embodiment, the autonomous downhole tool 755 further comprises a
spacing component 900, shown coupled to the bottom thereof for
positioning the autonomous downhole tool 755 with respect to a
feature in the well bore 120.
[0046] The navigation system 756 operably connects to the
autonomous downhole tool 755 to provide a determination of the
location of the tool 755 as it traverses the well bore 120. By way
of example, an operable connection may be provided by a mechanical,
electrical, hydraulic or wireless connection between two
components, such as the navigation system 756 and the tool 755. In
general, the navigation system 756 senses at least one parameter
and determines the location of the tool 755 within the well bore
120 based on the sensed parameters. Specifically, the navigation
system 756 determines the absolute location of the tool 755 within
the well bore 120 relative to a known reference, such as a well
bore feature, a formation feature, a surface feature, a global
positioning system (GPS), or a combination thereof. In an
embodiment, the navigation system 756 locally determines the
location of the tool 755 within the well bore 120 without receiving
location communications from the surface 105. In an embodiment, the
navigation system 756 determines the location of the tool 755
within the well bore 120 based on parameters sensed within the well
bore 120. In an embodiment, the navigation system 756 is further
operable to determine an azimuth orientation of the tool 755 within
the well bore 120.
[0047] In more detail, FIG. 5 is a block diagram of the autonomous
downhole tool 755 comprising an exemplary onboard navigation system
756 and at least one functional component 763. In an embodiment,
the onboard navigation system 756 comprises a first sensor 757
operable within the well bore 120 to sense a first parameter, a
second sensor 759 operable within the well bore 120 to sense a
second parameter, and a locator component 761. While two sensors
are illustrated in FIG. 5, it should be understood that a single
sensor or a plurality of sensors, including three or more sensors,
may be used. The first sensor 757 and the second sensor 759 provide
the sensed parameters to the locator component 761. The locator
component 761 then uses the sensed parameters to determine a
location of the tool 755 within the well bore 120. The locator
component 761 may further comprise a well bore log 765 and a
mission program 767. In various embodiments, the locator component
761 may provide a trigger signal to the functional component 763
based on the mission program 767, on the location of the tool 755
within the well bore 120, on another metric derived from the
location of the tool 755, such as a velocity of the tool 755, or
combinations thereof. The locator component 761 may be a computing
component, such as a circuit board having a CPU, memory, and
desired connectivity and communication interfaces and
functionality. While the locator component 761 of FIG. 5 is
positioned onboard the tool 755, in an alternative embodiment, the
locator component 761 is operably connected to the sensors 757, 759
and may be positioned at the surface 105 or within another downhole
component 150. Such a locator component 761 may communicate with
the tool 755 via wireless communications (e.g. electronic signals,
acoustic signals, or pressure pulses generated in a fluid flowing
into the well bore 120); via a non-supportive communication line,
or via other known communication means. Examples of non-supportive
communication lines include microtubing, microwire, microfiber,
fiber optics, and the like.
[0048] The first sensor 757 is operable within the well bore 120 to
sense a corresponding first parameter, for example a structure of
the well bore 120, such as a casing collar (e.g., a casing collar
locator), a formation characteristic (e.g., a gamma/neutron
profile), a pipe marker, a coded pipe marker, an electrical
impedance or a magnetic characteristic of the well bore casing 125,
a pipe inside surface characteristic, a geometry of the pipe, a
well bore deviation, or other feature of the well bore 120, well
bore casing, or lithologic formation surrounding the well bore 120.
In an embodiment, the first sensor 757 may be classified as a
structured-environment type sensor since it is directed to sensing
features of a structured environment. In alternative embodiments,
other types of sensors as described herein may be selected as each
of a plurality of sensors (e.g., a first sensor, second sensor,
etc.).
[0049] The first sensor 757 is operably connected to the locator
component 761, and the locator component 761 analyzes the first
parameter provided by the first sensor 757. The locator component
761 compares the first parameter to a corresponding first reference
standard, for example the well bore log 765. By comparing the first
sensed parameter to a first reference standard, the locator
component 761 is able to determine the location of the tool 755
within the well bore 120. The determination of the location of the
tool 755 based on the first sensed parameter and on a first
reference standard may be referred to as a first location estimate.
The first location estimate may be termed a discrete or quantized
metric of the location of the tool 755 because the values of the
first location estimate are confined to the values associated with
the first sensed parameter and the corresponding first reference
standard, for example casing collar locations, and may exclude
other locations that lie between.
[0050] In an embodiment wherein the first sensor 757 is a
structured-environment type sensor that senses coded pipe markers,
the coded pipe markers may provide specific location, position, or
displacement information, which reduces errors of calculating or
determining the location of the tool 755. The information is
encoded in each coded pipe marker. The first sensor 757 reads the
coded information, and the locator component 761 decodes the
information and uses the information to determine the location of
the tool 755 within the well bore 120. In an embodiment, the first
sensor 757 may decode the information and provide the locator
component 761 with location information. Additional well bore
intervention may be required to generate and to position these
coded pipe markers during well construction or during separate
post-construction serving operations.
[0051] In another embodiment, the pipe markers sensed by the first
sensor 757 may be uncoded. A plurality of uncoded markers may be
used as an alternative to casing collars for determining the
location of the tool 755, either in a simple counting algorithm, or
with a more complex mapping scheme. Widely spaced markers, either
coded or uncoded, may identify key positions in the well bore 120.
The widely spaced markers may also provide an additional error
correction check in a conventional collar locator based system.
Uncoded markers may be more easily detected than magnetically
detected casing collars. Such markers may detect mechanical
internal diameter changes, changes in the dielectric permittivity,
and changes in the dielectric permeability, for example, and may be
magnetic, optical, radiological, or combinations thereof.
[0052] In an embodiment, the reference standard is a well bore log
765, for example a well bore log 765 previously created with
imaging software. The well bore log 765 may be created during
logging of the cased well bore 120, or alternatively, each segment
of pipe could be logged prior to placement in the well bore 120. In
alternative embodiments, the image of the casing 125, such as a
casing detail that records interior surface variations of the
casing pipe, may be made with an optical sensor, magnetic sensor, a
gamma/neutron sensor, or any other sensor that can repeatably
measure variations in the pipe or the formation F. Optical imaging
identifies key landmarks such as irregularly spaced perforations,
drill pipe cuts, slip marks, or distinct geometric features, such
as the horizontal lines generated by a collar gap spacing in a
casing segment. Magnetic imaging identifies variations in the
magnetic field of the pipe.
[0053] The well bore log 765 created with imaging software may be
compressed using known techniques to reduce the bandwidth, the
memory, and/or the computing requirements to use the well bore log
765. The well bore log 765 may be used in combination with object
recognition software to match the sensed parameters to the
identifying characteristics of the imaged well bore 120 contained
in the well bore log 765, thereby providing an indication of
location of the tool 755 within the well bore 120. Signal
processing may also be applied to improve the quality of the data
from the sensed parameters provided to the object recognition
software.
[0054] In one embodiment, the first sensor 757 may be a casing
collar locator (CCL) sensor, such as a curb feeler CCL or a giant
magnetoresistive (GMR) CCL, and the well bore log 765 may be a
cased-hole log. A casing collar is a thickening of an end of the
casing pipe to provide for threaded connections between pipes. Each
joint or segment of casing pipe includes two casing collars, one
casing collar at either end of the casing pipe. The combination of
two casing collars where two segments of casing pipe connect, one
casing collar on either segment of casing pipe, is commonly
referred to hereinafter as a casing collar. The curb feeler CCL may
measure force, strain, sound, acceleration, or combinations thereof
as the curb feeler CCL physically interferes with the gap between
passing collars. The curb feeler CCL may be a wiper plug or a
simple metal strip dragging against the casing wall.
[0055] Suitable GMR-CCLs are disclosed and described in U.S. Pat.
No. 6,411,084 to Yoo, and U.S. patent application Publication No.
US2002/0145423 A1 to Yoo, both of which are owned by the assignee
hereof, and are herein incorporated by reference for all purposes.
In other embodiments, alternate GMR-CCL designs may be employed. In
an embodiment, the first sensor 757 may be a CCL that comprises a
magnetic or capacitive proximity sensor that drags along the casing
wall and indicates gaps that may correspond to the connection
between two casing segments.
[0056] The well bore log 765 provides information defining the
length of each segment of casing pipe and the relative positions of
each segment of casing pipe in a particular well bore. The well
bore log 765 may consist of a sequence of numbers representing the
length of each segment of casing pipe wherein the sequence of the
numbers is directly associated with the sequence of the segments of
casing pipe--for example, the first number is the length of the
first segment of casing pipe which is located at the top of the
well, the second number is the length of the second segment of
casing pipe which is attached below the first segment of casing
pipe, the third number is the length of the third segment of casing
pipe which is attached below the second segment of casing pipe, and
so on. An alternative well bore log 765 format may include
additional information in a file structured into a plurality of
records or lines, wherein each record or line contains information
about one segment of casing pipe. Each record may comprise a number
of fields such as a length field containing a number representing
the length of the segment of casing pipe, a sequence field
containing a number representing the sequential position of the
segment of casing pipe, a diameter field containing a number
representing the diameter of the segment of casing pipe, and,
optionally, additional fields containing other information. These
and other formats known to those skilled in the art are
contemplated for use as the well bore log 765 by this
disclosure.
[0057] The locator component 761 will analyze the output of the
first sensor 757 to determine that a casing collar has been
located. By counting the casing collars that the tool 755
encounters as it traverses the well bore 120, the locator component
761 may determine the position of the tool 755 within the well bore
120 based on the well bore log 765. For example, when the first
casing collar is sensed by the first sensor 757, the locator
component 761 determines that the tool 755 has traversed the length
of the first casing segment into the well bore 120, which is looked
up by referencing the well bore log 765. When the second casing
collar is sensed by the first sensor 757, the locator component 761
determines that the tool 755 has traversed the length of the first
casing segment plus the length of the second casing segment into
the well bore 120, which is looked up by referencing the well bore
log 765, and so on. While the discussion of the cased-hole log type
of well bore log 765 and the determination of the first location
estimate above was directed to an embodiment employing the first
sensor 757, other embodiments employing alternative
structured-environment type sensors and alternative reference
standards may be used in a similar manner to determine the first
location estimate. The locator component 761 may also compare the
well bore log 765 with the sequence of well bore structures, for
example casing collars, detected as the tool 755 traverses the well
bore to match up a pattern of structure indicated in the well bore
log 765 to a pattern of structure detected by the locator component
761. This may provide a corroboration of structure detection which
may be used to correct structure detection errors.
[0058] In an embodiment the well bore log 765 contains a count of
casing segments in the well bore and an assumed casing segment
length. The first location estimate is then determined based on
adding the assumed collar segment length to the previous first
location estimate when a collar location is detected. Alternately,
the locator component 761 may determine the location of the tool
755 entirely in terms of casing segment sequence number. For
example, the tool 755 may be programmed to deploy into the well
bore 120 and self-activate along the 200.sup.th casing segment. In
another embodiment, the locator component 761 does not contain a
well bore log 765, but instead counts collar detection events as
the tool 755 traverses the well bore, and commands the tool 755 to
self-activate upon reaching a collar count specified in the mission
program 767.
[0059] The first location estimate may be subject to various
errors. For example, the indication provided by the first sensor
757 may be weak or indefinite, and consequently the locator
component 761 may not count a structural feature or other sensed
parameter, and the association of the location of the tool 755 to
the reference standard such as the well bore log 765 may be offset.
For example, if the casing segments are each forty feet long and
the casing collar corresponding to casing segment number 40 is
missed, the locator component 761 may determine the first location
estimate to be 1560 feet instead of 1600 feet--having failed to add
in the 40 foot length of a segment of casing pipe. An alternate
error is to mistakenly count a structural feature before it has
been encountered as the tool 755 traverses the well bore, for
example spuriously counting a casing collar because of a noise
spike in the indication from the first sensor 757.
[0060] The second sensor 759 is operable in a well bore 120 to
sense a corresponding second parameter. The first sensor 757 and
the second sensor 759 may be the same or different. In an
embodiment, the second sensor 759 senses a parameter that is
derived from and/or integrated with the first sensor 757, for
example a timer (i.e., the second sensor 759) responsive to a
casing collar locator (i.e., the first sensor 757).
[0061] In an embodiment, the second sensor 759 is different from
the first sensor 757. For example, in various embodiments, the
second sensor 759 comprises an absolute, relative, or cumulative
type sensor. Absolute type sensors rely on sensing physical
parameters that are independent of any well structures. Examples of
absolute type sensors include a sensitive gravity gradient sensor,
a hydrostatic pressure sensor, or a fixed length line attached to
an onboard line spool. Relative type sensors determine distance to
reference points. Examples of relative type sensors include
range-finding to surface, range-finding to bottom, range-finding to
a passive secondary device, and range-finding to an active
synchronized pinging source employing acoustic (e.g.,
time-of-flight), ultrasonic, radio frequency, and optical energy.
Cumulative type sensors count total time and/or distance from the
surface and accumulate error along the way, termed dead reckoning.
Examples of cumulative type sensors include flow meters which track
fluid passage, inertial integration sensors (e.g., integration of
acceleration data to estimate position), pipe tracking using either
a physical contacting tracking device such as a wheel counter
(i.e., odometry) or an optical or magnetic tracking device, a
timer, or a constant velocity timing sensor.
[0062] The second sensor 759 is operably connected to the locator
component 761, and the locator component 761 compares the second
sensed parameter to a reference standard to determine a second
location estimate. The reference standard used to determine the
second location estimate may be the same as the first reference
standard (e.g., a well bore log 765) or may be another (i.e.,
second) reference standard corresponding in type to the second
sensed parameter.
[0063] In an embodiment, the second location estimate may be termed
a continuous metric of the location of the tool 755 because the
value that the second location estimate may take corresponds to any
point along the well bore (in contrast to discrete increments or
intervals), to the extent and resolution permitted by the numerical
representation system employed by the locator component 761. For
example, whereas the first location estimate based on the
indication of structure provided by the first sensor 757 may take
successive values of about 40 foot increments (e.g., 40.37 feet,
79.57 feet, 120.17 feet, and so on), the second location estimate
based on the indication of the location of the tool 755 provided by
a hydrostatic pressure sensor may take multiple values and values
at non-discrete increments: 40.37 feet, 40.40 feet, 40.43 feet, . .
. , 52.00 feet, 52.03 feet, 52.06 feet, . . . , 79.51 feet, 79.54
feet, 79.57 feet, and so on. Because the second location estimate
is continuous, in the sense described above, the second location
estimate may be employed to extrapolate the location of the tool
755 beyond a discrete location determination of the first location
estimate, prior to reaching a subsequent discrete location
determination of the first location estimate. The second location
estimate may be subject to various errors, depending upon the
second sensor 759. For example, a hydrostatic pressure sensor
produces an indication of increasing hydrostatic pressure in the
well bore as the tool 755 descends further into a vertical well
bore 120 filled with fluid. The locator component 761 determines
the second location estimate based on the indication of hydrostatic
pressure from the hydrostatic pressure sensor 759 as compared to a
reference standard (e.g., a map, functional relationship, or
equation) of the hydrostatic pressure to the location of the tool
755 in the well bore 120. This reference standard may assume that
the fluid density is constant, such that variations of the fluid
density cause error in the second location estimate. Other errors
may be associated with the absolute, cumulative, and relative
sensor types and their corresponding reference standards.
[0064] In an embodiment, the second sensor 759 may comprise one or
more accelerometers or inertial sensors. In this embodiment,
inertial indications may be integrated with respect to time, either
by the locator component 761 or within the second sensor 759, to
produce an indication of the location of the tool 755 in a 6-axis
system. The 6-axis location includes position in a XYZ-coordinate
system as well as yaw, pitch, and roll rotations about these
axes.
[0065] The locator component 761 may determine a velocity of the
tool 755 traversing the well bore 120 by dividing a location
displacement by a time interval. The location displacement may be
determined based on successive values of the first location
estimate, the second location estimate, or combinations thereof.
The time interval may be determined from a clock internal to the
locator component 761 or from a separate timer component within the
tool 755. The locator component 761 may use the velocity of the
tool 755 to determine the correct location to trigger deployment of
a brake to slow the tool 755 sufficiently to activate the
functional component 763. For example, if the tool 755 is
traversing the well bore 120 at a relatively high velocity, the
locator component 761 may determine to trigger the deployment of
the brake 50 feet before the location desirable for activating the
functional component 763 whereas if the tool 755 is traversing the
well bore 120 at a relatively slow velocity, the locator component
761 may determine to trigger the deployment of the brake 25 feet
before the location desirable for activating the functional
component 763.
[0066] In an embodiment, the first sensor 757 and the second sensor
759 are identical sensors, or they sense an identical parameter, or
both, also referred to as diversity sensors. In various
embodiments, the diversity sensors 757, 759 may be arranged
radially, circumferentially, axially, or combinations thereof about
the tool 755. Where the diversity sensors 757, 759 are arrayed
axially, a lower sensor would be expected to sense a common
parameter at a time earlier than an upper sensor as the tool 755
traverses the well bore 120. The difference in time readings
between the lower and upper sensors may be correlated to the
velocity of the tool 755 traversing the well bore 120. Thus, a
sensed parameter may be attributed to noise or other sensing error
if there is not a corresponding time differential between the
sensing of the parameter by the diversity sensors 757, 759. Where
the diversity sensors 757, 759 are arrayed circumferentially or
radially, the diversity sensors 757, 759 would be expected to read
a commonly sensed parameter at about the same time. Thus, a sensed
parameter may be attributed to noise or other sensing error if a
time differential occurs between the sensing of the parameter by
the diversity sensors 757, 759. Furthermore, a radial array assists
corrections for the tool being off-centered in the well bore 120. A
radial array can also help to distinguish radially symmetric well
bore features, such as collars, from other anomalies, such as
perforations.
[0067] The amount of error in the first location estimate and the
second location estimate may vary depending upon the type of sensor
employed to determine the location estimate. For example, the
location estimation error associated with the
structured-environment type sensors is different from the error
associated with the absolute, cumulative, and relative type
sensors, and this difference may be used by the locator component
761 to reduce the overall error in estimating the location of the
tool 755 in the well bore 120. The error associated with the
structured-environment type sensors is a discrete or quantum error.
For example, when using the first sensor 757, missing a collar may
introduce an error equivalent to a length of casing, e.g., 40 feet,
into the first location estimate. The error associated with the
absolute, cumulative, and relative sensor types is a continuous
error and is typically a small error over a small displacement
along the well bore 120--for example a few inches over 160
feet--but may become large over the length of a well bore 120, for
example several yards over 16,000 feet.
[0068] Turning now to FIG. 6, a diagram of an exemplary casing
string 781 is shown for depicting the two types of errors discussed
above and how the first location estimate may be used to correct
the second location estimate and vice versa. For convenience, the
casing string 781 comprises eight segments of pipe connected
serially, with the understanding that longer lengths of casing are
typically employed. For purposes of this example, each segment of
casing pipe is assumed to be exactly forty feet long and such
information is captured in the well bore log 765. The E1 column 783
indicates the first location estimate at various locations of the
tool 755 as it moves into the well bore 120. The E2 column 785
indicates the second location estimate at various locations of the
tool 755 as it moves into the well bore 120. The AB column 787
indicates the absolute location of the tool 755 as it moves into
the well bore 120.
[0069] In this embodiment, the first sensor 757 is a CCL sensor and
the second sensor 759 is a continuous sensor, such as a cumulative
distance meter. At a first string location 781 a the absolute
location, the first location estimate, and the second location
estimate listed in the AB column 787, the E1 column 783, and the E2
column 785, respectively, are all 0. At a second string location
781b, the second location estimate shown in the E2 column is 4
feet. The second location estimate is continuous as the tool 755
traverses the well bore 120 and cumulative along the entire length
of the casing string 781. At the second string location 781b, the
first location estimate remains unchanged at 0 feet because the
first sensor 757 has not detected a casing collar.
[0070] At a third string location 781c, the first and second casing
segments connect at a casing collar. When the tool 755 arrives at
the third string location 781c, the locator component 761 analyzes
the first sensor 757 sensed parameter to detect a casing collar and
adds the length of the casing segment, indicated by the well bore
log 765 to be forty feet, to the first location estimate of 0 to
provide an updated first location estimate of 40 feet. To the
extent that the well bore log 765 is accurate, the first location
estimate is accurate at the third string location 781c.
[0071] Also at the third string location 781c, the second sensor
759 indicates a depth of 40.5 feet. Thus, an error of 0.5 feet has
developed in the second location estimate. While this error is
small, an error of 0.5 feet per casing segment grows to 50 feet of
error after the tool 755 traverses 100 casing segments, a distance
of approximately 4000 feet. Since the first location estimate is
accurate, the locator component 761 could correct the second
location estimate to equal 40 feet, for example by resetting the
second sensor to zero. This is an example of using the first
location estimate from the first sensor 757 to correct or to
recalibrate an erroneous second location estimate from the second
sensor 759. Additionally, the first location estimate could be used
to re-estimate the change in voltage with respect to depth of the
second sensor 759.
[0072] At a fourth string location 781d, the first location
estimate is incremented by the locator component 761 to 80 feet,
and the second location estimate is determined by the locator
component 761 to be 81.0 feet. At a fifth string location 781e the
casing collar locator sensor 757 fails to detect the casing collar
located at the fifth string location 781e, and hence the first
location estimate remains unchanged at 80 feet, which is an error
of 40 feet. The second location estimate from the second sensor 759
is 121.5 feet.
[0073] At a sixth string location 781f, the first location estimate
is incremented by the locator component 761 to 120 feet, and the
second location estimate is determined by the locator component 761
to be 162.0 feet. At the sixth string location 781f, the second
location estimate of 162.0 feet could be used by the locator
component 761 to deduce that the casing collar at the fifth string
location 781e was overlooked. While the locator component 761 may
expect some error in the second location estimate, an error of 40
feet in the second location estimate is not plausible given the
nature of the error expected for the second sensor 759. The
plausible explanation is that the casing collar at the fifth string
location 781e was overlooked, and the first location estimate
should be adjusted to account for the casing collar at the fifth
string location 781e and the sixth string location 781f. This is an
example of using the second location estimate to correct the first
location estimate, which may be referred to as corroborating the
first location estimate.
[0074] At a seventh string location 781g, the locator component 761
erroneously detects a casing collar and increments the first
location estimate in the E1 column 783 to 160 feet. Assuming that a
correction has not already been made, the erroneous or spurious
detection of a casing collar compensates for the earlier erroneous
failure to detect a casing collar at the fifth string location
781e. The double counting of collars, i.e., the spurious detection
of casing collars, typically does not exactly balance the skipped
counting of collars, and the error tends to increase proportionally
to the square root of the number of collars measured.
[0075] At an eighth string location 781h, the locator component 761
correctly detects a casing collar and increments the first location
estimate to 200 feet. At a ninth string location 781k, the locator
component 761 erroneously detects a casing collar and increments
the first location estimate to 240 feet. The locator component 761
determines the second location estimate at the ninth string
location 781k to be 218 feet. The second location estimate is in
error versus the absolute location of 215.3 feet, but is accurate
enough to conclude that the detection of the casing collar is
spurious and hence that the locator component 761 should disregard
the spurious casing collar detection event. This would be another
example of using the second location estimate to correct the first
location estimate. As a result, the first location estimate is
corrected to 240 at the tenth string location 781m, and remains
accurate for the remainder of the string locations 781n and 781p in
comparison to the absolute location.
[0076] The discussion of FIG. 6 provides an example of how the
first location estimate may be used to correct the second location
estimate and vice versa. Note that if the first location estimate
has been corroborated by reference to the second location estimate,
the first location estimate may be used to recalibrate the second
location estimate at each casing collar, thus limiting the error
that accumulates in the second location estimate.
[0077] Turning now to FIG. 7, a flow chart depicts an embodiment of
a method for corroborating a first location estimate and
recalibrating a second location estimate, which may be referred to
as data or sensor fusion. Such a method may be implemented via the
locator component 761, for example in software, firmware, or
combinations thereof. The values of the first and second location
estimates are represented by E.sub.1 and E.sub.2, respectively. The
method begins at block 851 where the locator component 761 is
initialized. Initialization includes downloading a reference
standard (e.g., the well bore log 765) and the mission program 767
in the locator component 761, for example, in a random access
memory area accessible to the locator component 761. The well bore
log 765 and the mission program 767 may be downloaded to the
locator component 761, for example from a computer in communication
with the locator component 761 prior to deploying the tool 755 into
the well bore 120.
[0078] The embodiment shown in FIG. 7 uses a structured-environment
type sensor as the first sensor 757 and a well bore log 765 to
identify the position of casing segments. Those skilled in the art
may readily adapt this exemplary method description to alternate
embodiments, also contemplated by this disclosure, which may employ
other structured-environment type sensors as the first sensor 757.
Initialization also includes initializing a log pointer to
reference the log information in the well bore log 765 associated
with the first casing segment. As the following method proceeds,
the log pointer will successively be reassigned to reference the
log information in the well bore log 765 associated with other
casing segments in the casing pipe. It is understood that sometime
after initialization, the tool 755 is deployed into the well bore
120, and the method of FIG. 7 enters a continuous loop 852.
[0079] The method proceeds to block 853 where the locator component
761 receives the input (e.g., a sensed parameter) from the first
sensor 757, represented by S.sub.1 in FIG. 7, and analyzes the
input from the first sensor 757. The first sensor 757 provides a
first sensed parameter relating to a structure in the well bore
120. For example, the first sensor 757 provides an indication of
casing collars.
[0080] The method proceeds to block 855 where, if no structure is
detected, the method returns to block 853. If a structure is
detected, the method proceeds to block 857 where a preliminary
first location estimate, represented by PE.sub.1 in FIG. 7, is
determined. The information associated with a segment of the casing
pipe is read from the well bore log 765 using the log pointer as a
reference to the information. The length of the segment of casing
pipe between connections is represented by .DELTA..sub.log in FIG.
7. The value of .DELTA..sub.log may be different for each segment
of casing pipe. The value of the preliminary first location
estimate, represented by PE.sub.1, is assigned the value of the sum
of the first location estimate plus the length of the segment of
casing pipe. This is represented as
PE.sub.1=E.sub.1+.DELTA..sub.log. PE.sub.1 is said to be the
preliminary first location estimate and is distinguished from
E.sub.1 the first location estimate, because the indication of a
casing collar from the first sensor 757 may be spurious.
[0081] The method proceeds to block 859 where the preliminary first
location estimate PE.sub.1 is evaluated to determine if it is
within a reasonable range of values for the location of the tool
755. The preliminary first location estimate PE.sub.1 is compared
to the second location estimate, E.sub.2. If PE.sub.1 is greater
than E2 (which may be a cumulative location) and a maximum error
attributable thereto, then PE.sub.1 is deemed out of range and the
method returns to block 853, without modifying the value of the
first location estimate E.sub.1. In this case, indication of a
casing collar from the first sensor 757 is judged to be spurious
and is ignored.
[0082] If PE.sub.1 is not greater than E.sub.2 and a maximum error
attributable thereto, then PE.sub.1 is deemed in range and the
method proceeds to block 861 where the first location estimate
E.sub.1 is assigned the value of the preliminary first location
estimate PE.sub.1. In this case, the indication of a casing collar
from the first sensor 757 is judged to be valid and the estimated
location updated accordingly.
[0083] The method proceeds to block 863 where the log pointer is
incremented to reference the information associated with the
subsequent casing segment in the well bore log 765. The next time
the locator component 761 accesses the well bore log 765, as at
block 865, the information associated with a different casing
segment will be accessed from the well bore log 765.
[0084] The method proceeds to block 865 where the preliminary first
location estimate is redetermined following the same logic employed
in block 857. The method proceeds to block 867 where the
preliminary first location estimate is evaluated according to the
logic employed in block 859. If PE.sub.1 is deemed out of range,
the method proceeds to block 869.
[0085] If PE.sub.1 is deemed in range, the method returns to block
861 where the first location estimate E.sub.1 is again assigned the
value of the preliminary first location estimate. In this case
E.sub.1 has been incremented twice. This may be the case if the
first sensor 757 overlooked a casing collar when the tool 755
passed the casing collar. The method continues to loop through
blocks 861, 863, 865, and 867 until the preliminary first location
estimate is deemed out of range; whereafter the method proceeds to
block 869. The looping through blocks 861, 863, 865, and 867
accommodates the case when the first sensor 757 misses one or more
casing collars. When the method proceeds to block 869 the first
location estimate may be said to have been corroborated by the
second location estimate.
[0086] At block 869 the second location estimate is recalibrated
based on the corroborated value of the first location estimate,
after which the method returns to block 853. In an embodiment, the
second location estimate, E.sub.2, is a linear function of the
sensed parameter provided by the second sensor 759. This may be the
case, for example, if the second sensor 759 provides an indication
of hydrostatic pressure, cumulative distance, or time in the well
bore 120. Then E.sub.2 may be determined as E.sub.2=aP+b, wherein P
represents the well bore indication, and a and b are constants.
When the method enters block 869, the first location estimate is
presumed to be accurate, hence the equation E.sub.1=E.sub.2=aP+b
can be solved to recalibrate the constant value b to fit the
equation to the known location given by E.sub.1. This may be
considered a first level of recalibration. A second level of
recalibration may redetermine both constants a and b. This may be
accomplished by storing the value of E.sub.1 and the well bore
indication P provided by the second sensor 759 from the previous
(i.e., old) structure detection event and solving a system of
equations such as the following for a and b using well known
methods of linear algebra:
E.sub.1,old=aP.sub.old+b
E.sub.1,new=aP.sub.new+b
[0087] Alternative types of sensors may be used that sense one or
more parameters that are acceptably approximated as a linear
function of displacement into the well bore 120 over a distance of
several casing segments. Alternately, similar function fitting may
be performed for non-linear sensor indications using methods well
known to the mathematical art.
[0088] Other recalibration techniques may employ Markov Decision
Process, Kalman filter, neural network filter technologies, or
combinations thereof, all of which are contemplated by the present
disclosure. Further, these techniques may be used as the basis for
the estimation of location. Instead of requiring either sensor
measurement to be the accurate estimate of location, the sensor
measurements may be combined into an estimation process to provide
the location. For example, in a Kalman estimator the first
parameter, the second parameter, the time rate of change of the
first parameter, and the time rate of change of the second
parameter may be input into the estimator. A Kalman estimator is
typically a state-space representation that includes the dynamics
of the system. In some embodiments, the output from the Kalman
estimator may provide a preferred estimate for the location. If the
error of the measurements can be cast as a structured uncertainty
rather than as a random uncertainty, the weighting used to create
the Kalman estimator can be weighted to minimize the effects of the
structured uncertainty. In some embodiments, a Kalman estimator is
preferred, such as where neither of the sensors 757, 759 is a
structured-environment type sensor.
[0089] Recalibration may be particularly useful if the second
sensor 759 is a hydrostatic pressure sensor, since the hydrostatic
pressure in the well bore 120 varies linearly with displacement
along the well bore 120 only if the fluid density is uniform
throughout the entire well bore 120, which may not be the case.
Other sensors may also depend upon an assumed uniform well bore
characteristic which may not in fact be uniform, and hence these
other sensors may particularly benefit from recalibration also.
[0090] A supplementary corroboration may be provided by identifying
a short segment of casing in a sequence of long segments of casing.
For example, if the 50.sup.th casing segment is 30.12 foot long and
the five casing segments on either side of the 50.sup.th casing
segment are all approximately 40 foot long, detecting this short
casing segment can be used to corroborate the location of the tool
755.
[0091] The above method may be adopted for use with one or more
additional primary (i.e., E.sub.1) and secondary (i.e., E.sub.2)
sensors selected from the structural, absolute, relative, and
cumulative sensor types. In an embodiment, E.sub.2 is provided by a
combination selected from absolute, relative, and cumulative
sensors. In this case the corroborating indication E.sub.2 may be
selected from among several sensed parameters provided by the
combination based on a determination of which of these sensors is
providing the most accurate location indication at that time. When
the first location estimate is updated, hence when the first
location estimate is corroborated, each of the sensors in the
combination may then be recalibrated against the known location
provided by the corroborated first location estimate.
[0092] In an embodiment where the first sensor 757 and the second
sensor 759 are identical sensors that are arrayed axially about the
tool 755, the difference in time readings between the first sensor
757 and the second sensor 759 may be correlated to the downward
velocity of the tool 755, as mentioned above. Additionally, the
downward velocity of the tool 755 may be determined from successive
structured-environment detections, for example casing collar
detections, by dividing the distance between the
structured-environment detections indicated in the well bore log
765 by the time it takes to traverse this distance. The locator
component 761 may determine the first location estimate based on
the parameters sensed by the first sensor 757 and the second sensor
759. The downward velocity of the tool 755, represented as V, may
be employed by the locator component 761 to determine the second
location estimate, as by determining a displacement .DELTA.D during
a short interval of time dt as .DELTA.D=V.multidot.dt and by
determining the second location estimate E.sub.2 as the sum of
these displacements: E.sub.2=.SIGMA.(.DELTA.D)=.SIG-
MA.(V.multidot.dt). Since velocity may not be constant, this
equation may be modified to
E.sub.2=.SIGMA.(.DELTA.D.sub.i)=.SIGMA.(V.sub.i.multidot.d- t), the
sum of displacements of the tool 755 along the well bore 120
determined over relatively short intervals of time, using updated
values of velocity V.sub.i determined using successive values of
the first location estimate, reducing the error of the second
location estimate. The second location estimate may be employed to
reduce the error of the first location estimate, similarly to the
processes described above. In the case where the first sensor 757
and the second sensor 759 are both CCL sensors, the second location
estimate may be employed to corroborate the detection of casing
collars as described above.
[0093] The above method is directed to corroborating a first
location estimate and recalibrating a second location estimate. In
an embodiment, the locator component 761 may at all times employ
the second location estimate E.sub.2 as the preferred estimate of
the location of the tool 755 within the well bore.
[0094] Although the discussion of data or sensor fusion above is
directed to an application in the autonomous downhole tool 755,
those skilled in the art will readily appreciate that data or
sensor fusion also may be used to advantage with traditional
downhole tools. For example, logging tools are often used in
positioning downhole tools in the wellbore 120, wherein the logging
tool sends an indication of location to the surface. The accuracy
of the logging tool may be improved, according to the present
disclosure, by using the technique of data or sensor fusion to
determine location or simply to improve the accuracy of the logging
tool. For example, the logging tool may contain the first sensor
757, the second sensor 759, and the locator component 761. The
locator component 761 may be modified to couple to a communication
module within the logging tool whereby the locator component 761
provides the indication of location to the communication module,
and the communication module transmits the indication of location
to the surface 105 using well known communication mechanisms.
Alternatively, the locator component 761 is operably connected to
the sensors 757, 759 and may be positioned at the surface 105 or
within the logging tool. Such a locator component 761 may
communicate with the tool 755 via wireless communications (e.g.
electronic signals, acoustic signals, or pressure pulses generated
in a fluid flowing into the well bore 120); via a non-supportive
communication line, or via other known communications means.
Examples of non-supportive communication lines include microtubing,
microwire, microfiber, fiber optics, and the like. Thus, the
present disclosure contemplates the use of data or sensor fusion in
traditional tools, including but not limited to tools that
self-motivate or are self-propelled (e.g., robotic tools), tools
that are conveyed through the well bore via traditional conveyance
means, tools that send and receive location communications, tools
that are not self-activating, and the like.
[0095] Turning now to FIG. 8, a flow chart depicts another
embodiment of a method for corroborating the first location
estimate and recalibrating the second location estimate. In this
embodiment, the first sensor 757 is a CCL sensor providing a gross
measurement, and the second sensor 759 is a hydrostatic pressure
sensor providing a fine measurement. The method begins at block 951
where the locator component 761 is initialized. Initialization
includes downloading the well bore log 765 and the mission program
767 in the locator component 761, for example in a random access
memory area accessible to the locator component 761. The well bore
log 765 and the mission program 767 may be downloaded to the
locator component 761 from a computer in communication with the
locator component 761 prior to deploying the tool 755 into the well
bore 120. The well bore log 765 may identify the lengths of casing
segments as well as other pertinent details of the casing string.
Initialization includes initializing a log pointer to reference the
log information in the well bore log 765 associated with the first
segment of casing pipe. As the following method proceeds, the log
pointer will successively be reassigned to reference the log
information in the well bore log 765 associated with other segments
of casing pipe. It is understood that sometime after
initialization, the tool 755 is deployed into the well bore 120,
and a continuous loop 952 is entered.
[0096] The method proceeds to block 953 where the locator component
761 monitors the output of the CCL. The method proceeds to block
955. If the output from the first sensor 757 does not exceed a
threshold, then the method returns to block 953. If the output from
the first sensor 757 exceeds the threshold, which may be termed a
"threshold event", the method proceeds to block 957 where a
pressure differential is determined, represented by dP in FIG. 8.
The threshold event is considered uncorroborated until later. The
sensed pressure differential dP is determined from the current
indication of hydrostatic pressure output by the second sensor 759
and the indication of hydrostatic pressure output by the second
sensor 759 when the last corroborated threshold event occurred.
[0097] The method proceeds to block 959 where the locator component
761 reads the information in the well bore log 765 referenced by
the log pointer, determines the length of the casing segment
according to the information read from the well bore log 765, and
determines an expected pressure difference across such length.
[0098] The method proceeds to block 961 where if the sensed
pressure difference is close to the expected pressure difference
then the method proceeds to block 963, otherwise the method
proceeds to block 965. In block 963 the first location estimate is
updated by adding the increment of length indicated by the
information in the well bore log 765 referenced by the log pointer
to the existing value of the first location estimate. The log
pointer is incremented to point to the next casing segment
information in the well bore log 765. The method proceeds to block
967 where the second location estimate is recalibrated as discussed
above.
[0099] In block 965 if the pressure difference is close to twice
the expected pressure difference then the method proceeds to blocks
969 and 971, otherwise the method returns to block 953. In block
969 the first location estimate is updated a first increment by
adding the increment of depth indicated by the information in the
well bore log 765 referenced by the log pointer to the old value of
the first location estimate. The log pointer is updated (e.g.,
incremented) to point to the next casing segment information in the
well bore log 765. The method proceeds to block 971 where the first
location estimate is updated a second increment by adding the
increment of length indicated by the information in the well bore
log 765 referenced by the updated log pointer. The log pointer is
updated again (e.g., incremented a second time) to point to the
next casing segment information in the well bore log 765. The
method proceeds to block 967 where the second location estimate is
recalibrated as discussed above. When the method proceeds to block
967 the first location estimate is considered to have been
corroborated and the associated threshold event is also considered
corroborated.
[0100] The mission program 767 provides commands or event-response
pairs that the locator component 761 uses to trigger functions
provided by the functional component 763, as described in more
detail herein. The mission program 767 may comprise a computer
program or software routine that the locator component 761 may
invoke. Alternately, the mission program 767 may be a table, a
file, or other structure containing data which associates a well
bore location, for example a depth of 16,000 feet, with a function
trigger, for example deploying a frac plug. The mission program 767
may be said to customize the generic functionality of the locator
component 761 to provide specific functions for a specific well
bore 120.
[0101] Referring again to FIG. 4, the autonomous downhole tool 755
may comprise one or more functional components 763 to perform any
number of functions at one or more locations sensed by the
autonomous downhole tool 755. By way of example only, the
functional components 763 may be operable to perforate the well
bore casing 125; evaluate the formation F; evaluate another
downhole component 150, such as a well bore assembly, for example;
isolate a segment of the well bore 120; release a detachable
component 800 of the tool 755, or any combination thereof.
[0102] In an embodiment, one functional component 763 of the
autonomous downhole tool 755 is a rotator operable to rotate the
tool 755 to a desired azimuth orientation within the well bore 120.
In an embodiment, the rotator comprises a mechanical interface on
the bottom of the tool 755 operable to engage a mating element on
the top of another downhole component 150, thereby rotating the
tool 755 to a desired azimuth orientation with respect to the
downhole component 150. In another embodiment, the rotator
comprises a motor operable to rotate the tool 755 to a desired
azimuth orientation. In an embodiment, the motor is activated based
on data from an azimuth sensor, such as a gyro.
[0103] It may be desirable to control the descent of the tool 755
within the well bore 120, for example, so as to prevent damage to
the tool 755 at diameter changes in the casing 125, so as to
prevent high stresses on the tool 755 when it stops, or so that the
tool 755 does not overshoot the target location. Thus, in an
embodiment, one functional component 763 of the autonomous downhole
tool 755 is a braking system 760 operable to dissipate the linear
kinetic energy of the tool 755 as it traverses the well bore 120.
The braking system 760 controls the descent of the tool 755 so as
to slow the tool 755, stop the tool 755, or both. In an embodiment,
the braking system 760 utilizes a velocity proportional technique
to slow the tool 755 by applying a slowing force proportional to
the velocity of the moving tool 755. Thus, an increase in the
velocity of the tool 755 results in a corresponding increase in the
slowing force, and vice versa. In an embodiment, the braking system
760 utilizes a constant technique to slow and/or stop the tool 755
by applying a slowing force that is independent of the velocity of
the moving tool 755. Both the velocity proportional technique and
the constant technique convert the linear kinetic energy of the
moving tool 755 into another form of energy, such as thermal
energy, rotary kinetic energy, or electrical energy, for
example.
[0104] Various embodiments of braking systems 760 utilizing
velocity proportional techniques may be provided. In more detail,
in an embodiment, the braking system 760 comprises a fluid drag
component, such as a parachute, for example, to cause drag on the
descending autonomous downhole tool 755. A higher velocity of the
tool 755 would create more drag, thereby providing a relatively
constant rate of descent. The parachute could be rigid or flexible,
and it could be located above or below the tool 755.
[0105] In another embodiment, the braking system 760 comprises
flow-induced drag blocks that are forced against the casing 125 (or
uncased wall of the well bore 120) in response to a pressure
differential created between the upper and lower end of the tool
755 during descent. A higher velocity of the tool 755 would create
more pressure differential, thereby exerting a higher force between
the drag blocks and the casing 125 to slow the tool 755. Return
springs may be incorporated into the drag blocks to cause them to
retract when the tool 755 slows.
[0106] In an embodiment, the braking system 760 comprises magnets,
such as sheet magnets, button magnets, electromagnets, or
combinations thereof, for example, disposed towards the exterior of
the tool 755. As the tool 755 descends, eddy currents are generated
in the casing 125 to slow the velocity of the tool 755. In
particular, by moving the magnets along the metal casing 125, a
whirlpool of circulating charge, i.e. eddy currents, are generated
that quickly decay into heat. Thus, the linear kinetic energy of
the moving tool 755 is dissipated into heat via the eddy currents
created by the magnets.
[0107] In an embodiment, the braking system 760 comprises a
rotating wheel connected to a generator. The wheel engages and
rotates against the casing 125 or well bore wall as the tool 755
descends to produce electrical energy in the generator. A higher
velocity of the tool 755 leads to faster rotation of the wheel,
thereby creating a larger drag on the generator to slow the descent
of the tool 755.
[0108] In an embodiment, the braking system 760 comprises a feature
of the tool 755 that causes the tool 755 to spin as it descends in
the well bore 120. By way of example, a plurality of fins may be
disposed on the exterior of the tool 755 to cause it to spin. By
spinning the tool 755, the linear kinetic energy of the descending
tool 755 is reduced as it is transferred to rotary kinetic
energy.
[0109] Various embodiments of braking systems 760 utilizing
constant techniques to slow and/or stop the tool 755 may also be
provided. In more detail, in an embodiment, the braking system 760
comprises mechanical slips having teeth that bite into the casing
125. In an embodiment, the braking system 760 comprises drag
blocks, namely mechanical slips without teeth. The drag blocks may
be rigid blocks that follow the contour of the casing 125 or open
wall of the well bore 120, thereby producing a drag force opposite
the direction of travel. Alternatively, the drag blocks may have
flexible fingers that provide a slowing force while the blocks
provide a stopping force. Further, the drag blocks may comprise
magnets to increase the friction for stopping the tool 755.
[0110] In another embodiment, the braking system 760 comprises a
permanent magnet, an electromagnet, or a combined
permanent/electromagnet to create a frictional braking force. A
permanent magnet creates a constant attractive force between the
tool 755, or a component thereof, and the casing 125; whereas an
electromagnet is selectively operable to create an attractive force
between the tool 755, or a component thereof, and the casing 125.
The attractive force results in frictional drag with the casing
125, thereby slowing the autonomous downhole tool 755. Using a
combined permanent/electromagnet, selective operation of the
electromagnet may cancel the field generated by the permanent
magnet. Thus, a combined permanent/electromagnet provides a
releasable or controllable magnetic assembly for applying or
releasing the braking system 760.
[0111] In another embodiment, the braking system 760 comprises an
adhesive. In an embodiment, the adhesive is forced or injected into
the annular gap between the tool 755 and the casing 125. Such
adhesive may comprise a high viscosity that creates a frictional
drag against the casing 125, thereby slowing the tool 755.
Alternatively, such adhesive may comprise expansive properties to
create pressure against the casing 125, thereby slowing the tool
755. As the tool 755 slows, the adhesive increasingly adheres to
the casing 125, which eventually stops the tool 755. In another
embodiment, the adhesive is injected internally of the tool 755 to
close off a flowbore, for example, thereby preventing fluid flow
through the tool 755, which slows and/or stops the tool 755. The
adhesive may be thermosetting, such as an epoxy, or the adhesive
may be thermoplastic. The adhesive may further comprise a
cross-linking agent, and cross-linking may be accomplished by
chemical, electrical, or magnetic stimulation, or a combination
thereof.
[0112] In another embodiment, the braking system 760 comprises a
suction force created by hydraulic pressure. In yet another
embodiment, the braking system 760 comprises an inflatable chamber
that contacts the casing 125 or the open well bore wall, similar to
an inflatable packer, for example. Chemical out-gassing, compressed
pressure release, or pumped fluid, for example, could be used to
inflate the chamber to stop the tool 755.
[0113] Accordingly, in various embodiments, the braking system 760
comprises a fluid drag component, a pressure differential
component, an eddy current component, a generator component, a
rotary component, a mechanical component, a magnetic component, an
adhesive component, a suction component, an inflatable component, a
variable buoyancy component, or a combination thereof.
[0114] In an embodiment, the braking system 760 is operable to set
the tool 755 against a casing 125, or set the tool 755 against an
open hole wall in the well bore 120. In an embodiment, the braking
system 760 is releasable to unset the tool 755 from the casing 125
or from the open hole wall of the well bore 120. In an embodiment,
the releasable braking system 760 comprises a frangible component,
such as a shear pin or a rupture disc, for example, that is
fragmented to unset the tool 755.
[0115] In another embodiment, the releasable braking system 760
comprises a dissolvable material that is dissolved to unset the
tool 755. The dissolvable material may comprise a composition that
dissolves when exposed to a chemical solution, an ultraviolet
light, or a nuclear source, such as an epoxy resin, a fiberglass,
or a glass-reinforced epoxy resin, for example; a eutectic
composition that melts and flows away when heated; a composition,
such as an adhesive, for example, that degrades in a well bore
environment; a biodegradable material that degrades in a well bore
environment, or a combination thereof. Suitable biodegradable
materials are disclosed in copending U.S. patent application Ser.
No. 10/803,689 filed on Mar. 17, 2004, entitled "Biodegradable
Downhole Tools" (Attorney Docket No. HES 2003-IP-010245), and
copending U.S. patent application Ser. No. 10/803,668, filed on
Mar. 17, 2004, entitled "One-Time Use Composite Tool Formed of
Fibers and a Biodegradable Resin" (Attorney Docket No. HES
2003-IP-012174), which are both owned by the assignee hereof, and
are both hereby incorporated by reference herein for all purposes.
In an embodiment, the releasable braking system 760 comprises a
mechanical braking component coupled to the tool 755 via a
dissolvable material, such as an adhesive, for example. Thus, when
the adhesive dissolves, the tool 755 is released from the
mechanical braking component so that the tool 755 resumes
traversing the well bore 120 while the mechanical braking component
is left behind or falls to the bottom of the well bore 120.
[0116] In still another embodiment, the releasable braking system
760 may be selectively activated to slow or stop the tool 755, and
selectively deactivated to release the braking system 760 so that
the tool 755 resumes movement within the well bore 120. The braking
system 760 may be deactivated, for example, by retracting a
mechanical component or parachute; demagnetizing a magnetic
component; deflating an inflatable component; removing suction for
a suction component; reheating a thermoplastic adhesive component;
or by applying a counter force to the braking force. In an
embodiment, the releasable braking system 760 may be selectively
reactivated at another location in the well bore 120. Thus, a
selectively activated and deactivated braking system 760 is
operable at a plurality of well bore locations to slow or stop the
tool 755, then release the tool 755.
[0117] In an embodiment, the autonomous downhole tool 755 is
self-activating. In particular, referring again to FIG. 4, in an
embodiment, the autonomous downhole tool 755 comprises one or more
activators 790 operable to activate the one or more functional
components 763 of the tool 755, including the braking system 760,
at one or more locations in the well bore 120. In an embodiment,
the one or more locations are sensed by the navigation system
756.
[0118] In an embodiment, the activator 790 comprises a source of
energy stored on the tool 755, and a trigger for releasing the
stored energy to activate one or more of the functional components
763. The stored energy source may comprise mechanical, chemical,
electrical, or hydraulic energy, for example. In an embodiment, the
trigger comprises an electrically driven part, such as a pilot
valve or clutch. In an embodiment, the trigger comprises a spark to
start a chemical reaction or cause an explosion. In various
embodiments, the trigger of the one or more activators 790 releases
the stored energy in response to communications from the navigation
system 756; in response to communications from the surface 105,
such as via the cable 118, via a non-supportive communication line,
or via wireless communications (e.g. electronic signals, acoustic
signals, or pressure pulses generated in a fluid flowing into the
well bore 120); in response to communications from another downhole
component 150; or a combination thereof.
[0119] Thus, the one or more activators 790 may activate the one or
more functional components 763 of the tool 755 via a mechanical
operation, a chemical operation, an electrical operation, a
hydraulic operation, an explosive operation, a timer-controlled
operation, or any combination thereof.
[0120] By way of example only, in an embodiment, the trigger of the
activator 790 comprises an elastic spring that expands or a shear
pin that shears to release mechanical or hydraulic stored energy
for activating one or more functional components 763 of the tool
755.
[0121] In an embodiment, the trigger of the activator 790 starts a
chemical reaction that generates heat to activate one or more
functional components 763 by setting a phase change material, for
example, such as a shape memory alloy or a eutectic material. In
another embodiment, the trigger of the activator 790 starts a
chemical reaction that generates pressure to hydraulically activate
one or more functional components 763 of the tool 755. In yet
another embodiment, the trigger of the activator 790 starts a
chemical reaction that generates electricity for activating one or
more functional components 763. In still another embodiment, the
trigger of the activator 790 starts a chemical reaction that
generates a gas to activate one or more functional components 763,
such as to drive a piston, for example.
[0122] In other embodiments, the trigger of the activator 790 may
engage a battery or a capacitor to drive a motor or a lead screw,
for example, to gain mechanical advantage. In still other
embodiments, the trigger of the activator 790 may comprise a
rupture disc that ruptures or a pilot valve that opens to release
hydraulic energy to activate one or more functional components 763.
In further embodiments, the trigger of the activator 790 may
comprise an igniter to activate a detonator that generates an
impact load or a shock load, for example. As one of ordinary skill
in the art will appreciate, any combination of the various
embodiments of the activators 790 herein described, as well as
other types of activators, may be employed to activate one or more
functional components 763 of the tool 755.
[0123] In an embodiment, the autonomous downhole tool 755 comprises
one or more detachable components 800 operable to selectively
detach from the tool 755 within the well bore 120. In an
embodiment, the detachable component 800 is returnable to the
surface 105 after detaching from the tool 755. In various
embodiments, the detachable component 800 may be buoyant and ascend
in the well bore 120 to the surface 105 via buoyancy; or may be
flowable and ascend in the well bore 120 to the surface 105 via
circulation of a flowing fluid, or may be retrieved via a
connection to the surface 105, such as via cable 118, or a
combination thereof.
[0124] In an embodiment, the detachable component 800 comprises a
functional component 763 or combinations thereof. In an embodiment,
the detachable component 800 comprises an enclosure for holding a
fluid sample, a core sample, or a consumable component of the
autonomous downhole tool 755, for example. In an embodiment, the
detachable component 800 comprises the navigation system 756 or a
portion thereof, such as a memory component, for example. Thus, at
least a portion of the navigation system 756 may be returned to the
surface 105 and reused. In an embodiment, the detachable component
800 comprises a logging device 850 that is independent of the
navigation system 756. In an embodiment, the logging device 850 is
operable to sense and record parameters as the device descends with
the tool 755 in the well bore 120.
[0125] In another embodiment, the logging device 850 may be
provided as a separate component from the autonomous downhole tool
755. In an embodiment, the separate logging device 850 is
untethered to the surface 105 and is operable to sense and record
parameters as the device descends and ascends in the well bore 120.
In an embodiment, the separate logging device 850 does not
communicate with the surface 105 as it traverses in the well bore
120. In an embodiment, the separate logging device 850 is
sufficiently small so as not to create operational concerns or
safety hazards should the device 850 fail to return to the surface
105. In an embodiment, the separate logging device 850 is a
miniature logging device. In various embodiments, the separate
logging device 850 is less than approximately 1-inch in diameter,
less than approximately 3/4-inch in diameter, less than
approximately 1/2-inch in diameter, or less than approximately
1/4-inch in diameter. In an embodiment, the separate logging device
850 comprises a navigation system 756.
[0126] In various embodiments, the separate logging device 850
descends in the well bore 120 via a cable 118, fluid circulation,
gravity, or a combination thereof. In various embodiments, the
separate logging device 850 ascends in the well bore 120 via a
cable 118, fluid circulation, buoyancy, or both. In an embodiment,
the separate logging device 850 comprises a variable buoyancy body,
wherein buoyancy may be changed by releasing a mass, releasing a
positively buoyant component from a negatively buoyant component,
emptying a ballast tank, releasing a gas bubble, or inflating a
balloon, for example. In various embodiments, the descent and
ascent of the separate logging device 850 is controlled by time,
location, memory usage, or a combination thereof. The separate
logging device 850 may be used to verify that an autonomous
downhole tool 755 is set against the casing 125 in the proper
location within the well bore 120, for example.
[0127] Referring again to FIG. 4, in an embodiment, the autonomous
downhole tool 755 further comprises a spacing component 900. In
FIG. 4, the spacing component 900 is shown coupled to the bottom
thereof for spacing the tool 755 a distance from a location in the
well bore 120, such as a plug set at the location, the bottom of
the well bore 120, or a change in internal diameter of the well
bore 120 at the location, for example. One exemplary autonomous
downhole tool 755 may comprise a perforating gun with a spacing
component 900 coupled to the bottom thereof for positioning the gun
at a distance from a frac plug set in the well bore 120. In an
embodiment, the frac plug may also be an autonomous downhole tool
755.
[0128] In an embodiment, the spacing component 900 may be coupled
to the top rather than the bottom of the tool 755. Thus, the
spacing component 900 may position the tool 755 with either a
compressive load or a tensile load. The spacing component 900 may
also act to control the descent of a tool 755 that is free-falling
via gravity into the well bore 120. For example, the spacing
component 900 may comprise fins that cause the tool 755 to spin as
it moves within the well bore 120.
[0129] In another embodiment, the spacing component 900 is provided
as a separate component from the tool 755 and is releasable into
the well bore 120. In particular, the releasable spacing component
900 is disposed within the well bore 120 by being dropped, pumped,
released from a wireline, released from a coiled tubing, released
from a slick line, released from jointed pipe, or a combination
thereof. In an embodiment, the releasable spacing component 900 is
an autonomous downhole tool 755.
[0130] In an embodiment, the spacing component 900 has an
adjustable length comprising at least a first length that positions
the autonomous downhole tool 755 at a distance from the location
within the well bore 120, and at least a second length that
positions the tool 755 at approximately the location. In various
embodiments, the spacing component 900 is collapsible, foldable,
bendable, buckleable, or a combination thereof. Thus, the spacing
component 900 may be extended when the tool 755 is positioned at a
distance from the location, and the spacing component 900 may be at
least partially collapsed, folded, bent, buckled or a combination
thereof, when the tool 755 is positioned approximately at the
location. In an embodiment, the spacing component 900 is extendable
from a non-extended position, locks or sets in the extended
position to provide the desired spacing function, and subsequently
unlocks or unsets to return to the non-extended position.
[0131] In an embodiment, the length of the spacing component 900 is
extendable and/or adjustable, for example via fluid flow through
the spacing component 900. In an embodiment, such a spacing
component 900 comprises a telescoping body having an inner member
and an outer member, wherein at least one of the members is
moveable axially with respect to the other member in response to
fluid flow through the telescoping body. In an embodiment, the
length of the spacing component 900 is adjustable proportionately
to the flow rate of the fluid flowing through the telescoping
body.
[0132] In other embodiments, the spacing component 900 is
frangible, dissolvable, degradable, combustible, or a combination
thereof. In various embodiments, the spacing component 900
comprises magnesium, cast iron, a ceramic, a composite material, or
a combination thereof. Thus, the spacing component 900 may be
intact when the tool 755 is positioned at a distance from the
location, and the spacing component 900 may be at least partially
fragmented, dissolved, burned away, or a combination thereof when
the tool 755 is positioned approximately at the location. By way of
example only, a ceramic or brittle cast iron spacing component 900
may be fragmented using a detonation cord or a shock wave, such as
when a perforating gun is fired, for example; a magnesium spacing
component 900 may be chemically dissolved by an acid; a composite
spacing component 900 may be chemically dissolved by certain
caustic fluids; and a combustible spacing component 900 could be
burned away via a low-order detonation.
[0133] Further, a spacing component 900 comprising a flexible
material may buckle under a shock load or impact load imparted when
a perforating gun is fired, for example. In an embodiment, the
spacing component 900 comprises a segmented linkage, such as a
compound scissor mechanism, for example, that folds upon itself. In
an embodiment, the spacing component 900 comprises concentric tubes
with fragible shear pins that enable the tubes to collapse from a
fully-extended position.
[0134] In an embodiment, the spacing component 900 further
comprises an activation mechanism 950 that activates to adjust its
length, for example lengthening or shortening the spacer component
900. In various embodiments, the activation mechanism 950 comprises
a detonator, a chemical solution, a shear pin, a shock load, an
impact load, or a combination thereof. The activation mechanism 950
may be operable via a mechanical operation, a chemical operation,
an explosive operation, an electrical operation, a timer-controlled
operation, a hydraulic operation, or a combination thereof. In an
embodiment, the activation mechanism 950 is triggered by the
navigation system 756, such as, for example, to extend the length
of the spacing component 900 as it approaches a target location
within the well bore 120 and/or when the autonomous downhole tool
755 is being slowed by the braking system 760. In an embodiment,
the activation mechanism 950 is triggered in response to or in
coordination with the operation of one or more tools located
proximate the spacing component 900, for example upon firing of a
perforating gun spaced a distance by the spacing component 900.
[0135] The autonomous downhole tool 755 may take a variety of
different forms. In an embodiment, the tool 755 comprises a plug
that is used in a well stimulation/fracturing operation, commonly
known as a "frac plug." FIG. 9 depicts an exemplary autonomous frac
plug 1408 in a run-in position as the frac plug 1408 is being
pumped into the well bore 120 from the surface 105 or descends
within the well bore 120 via gravity, FIG. 10 depicts the frac plug
1408 in a set position against casing 125 in the well bore 120
wherein servicing fluid is prevented from flowing downwardly
through the frac plug 1408, FIG. 11 depicts the frac plug 1408 in
the set position wherein production fluid is permitted to flow
upwardly through the frac plug, and FIG. 12 depicts the frac plug
1408 in a flow-back position for returning the frac plug 1408 to
the surface 105 after the well stimulation/fracturing operation is
complete.
[0136] The frac plug 1408 comprises an elongated tubular body
member 210 with an axial flowbore 205 extending therethrough. An
optional wiper plug 270 is disposed at the upper end of the body
member 210. The wiper plug 270 comprises at least one set of wiper
blades 272 that act to form a sealing engagement with the casing
125 so that the plug 1408 may be pumped into the well bore 120. The
wiper plug 270 has an axial flowbore 275 extending therethrough
that is in fluid communication with the axial flowbore 205 through
the body member 210.
[0137] A cage 220 is housed within the wiper plug 270 for retaining
a ball 225 that operates as a one-way check valve. In particular,
when the frac plug 1408 is set, the ball 225 seals off the flowbore
205 to prevent servicing fluid from flowing downwardly through the
frac plug 1408, as depicted in FIG. 10, but the ball 225 allows
production fluid to flow upwardly through the flowbore 205, as
shown in FIG. 11.
[0138] A packer element assembly 230, which comprises at least an
upper sealing element 232 and a lower sealing element 234, extends
around the body member 210. An upper set of slips 240 and a lower
set of slips 245 are mounted around the body member 210 above and
below the packer assembly 230, respectively. In an embodiment, a
braking system 760 is disposed around the body member 210, below
the lower set of slips 245.
[0139] A tapered shoe 250 is provided at the lower end of the body
member 210 for guiding and protecting the frac plug 1408 as it
traverses the well bore 120. In an embodiment, the navigation
system 756 of the autonomous frac plug 1408 is disposed in the
tapered shoe 250 below the body member 210. In an embodiment, the
navigation system 756 is detachable and returnable to the surface
105. As previously described, the navigation system 756 may be
initialized at the surface 105 before the plug 1408 is deployed
into the well bore 120. Initialization may include providing the
navigation system 756 with a well bore log and a mission program
that identifies the one or more locations in the well bore 120 to
set the frac plug 1408. In an embodiment, an activator 790 for
activating the braking system 760 is also disposed in the tapered
shoe 250. In an embodiment, the activator 790 comprises a small
explosive charge that when detonated, opens a chamber to external
hydrostatic forces that activate the braking system 760.
[0140] Referring now to FIG. 10, to set the frac plug 1408 as
shown, the navigation system 756 determines the target location
within the well bore 120, as previously described, and the
activator 790 activates the braking system 760 as the frac plug
1408 approaches the location. The braking system 760 sets the lower
slips 245 of the plug 1408 against the casing 125. Then hydraulic
fluid forces from above the frac plug 1408 act against the wiper
plug 270 since flow is prevented through the flow bore 205 of the
frac plug 1408 by the ball 225. These hydraulic forces act to
compress the packer assembly 230 downwardly against the lower slips
245 and outwardly against the casing 125, thereby sealing off the
well bore 120 below the frac plug 1408. Once the packer assembly
230 is fully compressed, the upper slips 240 engage the casing 125,
thereby retaining the packer 230 in the set position.
[0141] Referring now to FIG. 11, after the frac plug 1408 has been
set to isolate a zone of the well bore 120 below the frac plug
1408, production fluids from the isolated zone may flow upwardly
through the frac plug 1408, thereby unseating the ball 225 from the
flowbore 205 to permit the production fluids to flow up the well
bore 120 for recovery at the surface 105, such as at the well
head.
[0142] After the well stimulating/fracturing operation is complete,
the frac plug 1408 may be removed from the well bore 120. In an
embodiment, to remove the frac plug 1408 from the set position of
FIG. 10, the braking system 760 releases, as previously described
herein, to unset the lower slips 245 from the casing 125. In an
embodiment, the frac plug 1408 is then returnable to the surface
105. In particular, referring now to FIG. 12, in an embodiment, at
least a portion of the cage 220 is selectively removable such that
once the lower slips 245 are unset, hydraulic fluid forces flowing
upwardly from the producing zone of the formation F below the frac
plug 1408, as represented by the flow arrow 260, act to move the
ball 225 upwardly, thereby sealing the flowbore 275 of the wiper
plug 270. In this position, the ball 225 prevents flow upwardly
through the flow bore 205 of the frac plug 1408. Further, in an
embodiment, the wiper plug 270 may be configured with selectively
reversible wiper blades 272 that can be flipped 180-degrees
top-to-bottom so as to provide wiper blades 274 that are oriented
in the opposite direction, as shown in FIG. 12. Alternatively, the
wiper plug 270 may be configured with two sets of selectively
retractable/extendable wiper blades 272, 274 that are oriented in
opposite directions from one another such that the wiper blades 272
for moving the frac plug 1408 downwardly within the well bore 120
may be retracted, and the wiper blades 274 for moving the frac plug
1408 upwardly within the well bore 120 may be extended. Therefore,
the upward force of the fluid 260 acting against the wiper plug 270
causes the upper slips 245 to disengage from the casing 125 and the
packer assembly 230 to decompress, thereby unsealing the well bore
120. Then the frac plug 1408 flows upwardly to the surface 105 in
the flow-back position depicted in FIG. 12.
[0143] In embodiments, a well bore zonal isolation device, such as
the frac plug 1408 described herein, or a perforating gun, is
movable along at least a partial length of the well bore 120 via an
external force and has a communication line connected from the
device 1408 to the surface 105. In an embodiment, the communication
line is non-supportive of the device 1408 in the well bore 120, in
contrast to the cable 118, which has the ability to support the
entire device 1408 as it is conveyed into or retrieved from the
well bore 120. The communication line is operable to provide
communications to and from the device 1408 located in the well bore
120, for example electronic or hydraulic communications. Examples
of communication lines include microtubing, microwire, microfiber,
fiber optics, and the like, and a source of such communication line
may be located at the surface 105 and fed out as the device 1408
traverses the well bore 120 or vice-versa.
[0144] In an embodiment, the device 1408 is pumped and/or
free-falls via gravity in the well bore 120, and the communication
line is sized such that it does not interfere with the pumping
and/or free fall. In an embodiment, the device 1408 comprises a
navigation system 756 as disclosed herein, for example a navigation
system 756 comprising at least two sensors 757, 759 located on the
device 1408. The sensors 757, 759 communicate with a locator
component 761 to determine the location of the device 1408, wherein
the locator component 761 may be located onboard the device 1408 or
at the surface 105 and communicating with the device via the
communication line.
[0145] In an embodiment, the device 1408 is operable in response to
the navigation system 756. For example, the zonal isolation device
1408 sets/releases or the perforating gun fires in response to the
navigation system 756. In an embodiment, the device 1408 comprises
a braking system 760 as disclosed herein, which may be responsive
to the navigation system 756. In an embodiment, the device 1408
comprises a spacing component 900 as disclosed herein, which may be
responsive to the navigation system 756. Alternatively, the spacing
component 900 may be operable in response to braking, for example
extending via inertial force.
[0146] In operation, the various embodiments of the autonomous
downhole tools 755 described herein may be employed to perform a
variety of different well servicing methods. In an embodiment, the
autonomous downhole tool 755 is deployed at least a partial length
into the well bore 120 via an external force, as described herein.
In an embodiment, the autonomous downhole tool 755 self-determines
its location as it traverses the well bore 120, as described
herein, without receiving location communications from an external
source. In an embodiment, the autonomous downhole tool 755 brakes
to self-slow and/or self-stop the tool 755, as described herein, at
one or more sensed locations in the well bore 120. In an
embodiment, the one or more locations are predetermined.
[0147] In an embodiment, the autonomous downhole tool 755
self-activates one or more functional components of the tool 755 at
a sensed location in the well bore 120 without receiving command
communications from an external source. By way of example, in an
embodiment, the tool 755 brakes to self-stop, then self-activates
to seal off a portion of the well bore 120, such as, for example,
to temporarily seal off a portion of the well bore 120 for well
servicing, or to permanently seal off a portion of the well bore
120 to abandon the well. In another embodiment, the tool 755 brakes
to self-slow or self-stop, then self-activates to create
perforations through the casing 125 and into the formation F. In
another embodiment, the tool 755 brakes to self-stop, then
self-activates to rotate to a desired azimuth orientation and set
against the casing 125 or a well bore wall. In another embodiment,
the tool 755 brakes to self-slow, then self-activates the spacing
component 900 to adjust its length as the tool 755 approaches a
target location within the well bore 120. In an embodiment, the
length of the spacing component 900 is adjusted via inertial force
in response to the braking action. For example, the spacing
component 900 extends via inertial force when the braking system
760 is activated. In an embodiment, the spacing component 900
extends and then locks into the extended position. In an
embodiment, the lock is releasable. As one of ordinary skill in the
art will appreciate, autonomous downhole tools 755 may be employed
to perform many other types of functions within the well bore
120.
[0148] In an embodiment, the autonomous downhole tool 755 releases
a releasable component 800 of the tool 755. In an embodiment, the
releasable component 800 is returned to the surface 105 via a
mechanical connection to the surface 105, via buoyant action, via
fluid circulation in the well bore 120, or a combination thereof.
In an embodiment, the releasable component comprises a portion of
the navigation system 756 or a separate logging device 850.
[0149] In an embodiment, after the tool 755 performs a function at
the sensed location, the autonomous downhole tool 755 releases the
brake to continue traversing the well bore 120. In an embodiment,
the autonomous downhole tool 755 reactivates the brake to self-slow
or self-stop at another sensed location in the well bore 120. In an
embodiment, the autonomous downhole tool '755 self-activates again
to perform the same function or one or more different functions at
another location in the well bore 120.
[0150] In an embodiment, the autonomous downhole tool 755 remains
in the well bore 120 permanently. In an embodiment, the autonomous
downhole tool 755 is removable from the well bore 120.
[0151] After an autonomous downhole tool 755 has completed its
intended function in the well bore 120, the tool 755, or a
detachable component 800 or a spacing component 900 thereof, may be
removed from the well bore 120. In an embodiment, the autonomous
downhole tool 755 is retrievable. In a retrievable embodiment, the
tool 755 may alter its buoyancy so that it floats to the surface
105 for retrieval. Alternately, the tool 755 may be flowable so
that it flows to the surface 105 in a fluid flowing in the well
bore 120 for retrieval. In another embodiment, the tool 755 may be
retrieved via a connection to the surface 105, such as via cable
118. As one of ordinary skill in the art will understand, other
retrieval methods, or a combination of retrieval methods may also
be employed.
[0152] In another embodiment, the autonomous downhole tool 755 is
disposable. In a disposable embodiment, the tool 755 may comprise
drillable materials, millable materials, or both, such that the
tool 755 is drilled or milled out of the well bore 120 after its
service is complete. Alternately, the tool 755 comprises an
effective amount of dissolvable material, such as an epoxy resin, a
fiberglass, or a glass-reinforced epoxy resin, for example, such
that the tool desirably decomposes when exposed to a chemical
solution, an ultraviolet source, or a nuclear source. In another
embodiment, the tool 755 comprises an effective amount of
biodegradable material such that the tool desirably decomposes over
time when exposed to a well bore 120 environment. Suitable
biodegradable materials are disclosed in copending U.S. patent
application Ser. No. 10/803,689, filed on Mar. 17, 2004, entitled
"Biodegradable Downhole Tools", and copending U.S. patent
application Ser. No. 10/803,668, filed on Mar. 17, 2004, entitled
"One-Time Use Composite Tool Formed of Fibers and a Biodegradable
Resin", as previously referred to herein.
[0153] Turning now to FIGS. 13A, 13B, 13C, and 13D, four stages of
a method for performing a fracturing well service job using at
least one autonomous downhole tool is depicted. Referring now to
FIG. 13A, a well bore configuration 1400 depicts a first autonomous
zonal isolation device 1408a set against the casing 1414 to isolate
the well bore zone below the device 1408a. In an embodiment, a
first set of perforations 1407 has been made through a casing 1414
and into the formation F so that the zone below the device 1408a
can be produced through the perforations 1407. In alternate
embodiments, the device 1408a is set for another reason, such as to
limit the quantity of service fluid required in the well bore 120
above the device 1408a, and therefore, no perforations 1407 are
required below the device 1408a.
[0154] To set the first autonomous zonal isolation device 1408a,
the device 1408a is initially deployed along at least a partial
length of the well bore 120 via an external force. In particular,
in various embodiments, the first autonomous zonal isolation device
1408a is lowered into the well bore 120 on a cable 118 as shown in
FIG. 1, pumped into the well bore 120 as shown in FIG. 2, released
into the well bore 120 to descend by force of gravity as shown in
FIG. 3, or a combination thereof. In an embodiment, the first
autonomous zonal isolation device 1408a is self-navigating, i.e.
the device 1408a is operable to self-determine its location as it
traverses the well bore 120. In an embodiment, as the first zonal
isolation device 1408a approaches the location where it will set,
for example, a predetermined location identified in a mission
program 767, the first zonal isolation device 1408a self-activates
a brake 760, as previously described herein, to slow the device
1408a. In an embodiment, when the first zonal isolation device
1408a arrives at the predetermined location, the device 1408a
self-activates to set against the casing 1414 and thereby seal the
well bore 120 without command communications from the surface
105.
[0155] In an embodiment, the first zonal isolation device 1408a
comprises a navigation system 756, and the navigation system 756,
or a portion thereof, is releasable for recovery to the surface
105, either through buoyant action or via fluid circulating in the
well bore 120. In an alternate embodiment, a separate logging
device 850 may be coupled to the top of the first zonal isolation
device 1408a. In this embodiment, the logging device 850 may be
released to return to the surface 105, either through buoyant
action or via fluid circulating in the well bore 120, for
example.
[0156] In another embodiment, the separate logging device 850 is
separately deployed into the well bore 120 to engage the set device
1408a and verify its location, then return to the surface 105. In
an embodiment, the separately deployed logging device 850 comprises
a variable buoyancy body such that the device 850 descends in the
well bore 120 via gravity to engage the set device 1408a, and then
alters its buoyancy to ascend in the well bore 120 through buoyant
action. In another embodiment, the separately deployed logging
device 850 is flowable such that the device descends and ascends by
flowing in a fluid being circulated in the well bore 120.
[0157] In another embodiment, the separate logging device 850 is
attached to the isolation device 1408a and deployed therewith into
the well bore 120. After the isolation device 1408a is set, the
logging device 850 is selectively detached from the isolation
device 1408a and returned to the surface 105 via buoyant action or
fluid circulation. Thereafter, the same logging device 850 may be
separately deployed into the well bore 120 via gravity or fluid
circulation to engage the set device 1408a to verify its location,
and then return to the surface 105 again via buoyant action or
fluid circulation.
[0158] The various embodiments of the logging device 850 may
collect logging information, such as information about properties
of the well bore 120, during descent into the well bore 120, during
ascent out of the well bore 120, or both. The logging information
may be retrieved from the logging device 850 at the surface
105.
[0159] Referring now to FIG. 13B and to well bore configuration
1402, a method for using a first perforating gun 1412a to create a
second set of perforations 1413 through the casing 1414 and into
the formation F beyond is depicted. In an embodiment, after the
first zonal isolation device 1408a is set against the casing 1414,
a first releasable spacing component 1410a and the first
perforating gun 1412a are deployed into the well bore 120. The
first releasable spacing component 1410a may be coupled to the
bottom of the first perforating gun 1412a, or it may be provided as
a separate component. In an alternate embodiment, the first
releasable spacing component 1410a may have been coupled to the top
of the first zonal isolation device 1408a and deployed therewith
into the well bore 120.
[0160] The first releasable spacing component 1410a and the first
perforating gun 1412a are either pumped or dropped into the well
bore 120 to free-fall by force of gravity, or both, until the first
releasable spacing component 1410a is stopped by contact with the
first zonal isolation device 1408a, and the first perforating gun
1412a is stopped by contact with the first releasable spacing
component 1410a. The first releasable spacing component 1410a has a
sufficient length to position the first perforating gun 1412a at a
desirable location to create perforations 1413 through the well
bore casing 1414 and into the formation F. Alternatively, the first
perforating gun 1412a may be deployed into the well bore 120 to
engage the first zonal isolation device 1408a directly without
having the first spacing component 1410a therebetween. The first
perforating gun 1412a fires in response to the deceleration of the
gun 1412a, in response to an expired on-board timer, in response to
another triggering means, or a combination of these or other known
arming or safety methods.
[0161] Referring now to FIG. 13C and to well bore configuration
1404, the first releasable spacing component 1410a has been reduced
in length to lower the first perforating gun 1412a substantially
clear of the second set of perforations 1413. Sometime during or
after the first perforating gun 1412a fires, the first releasable
spacing component 1410a may dissolve due to the presence of a
dissolving fluid introduced for this purpose into the well bore 120
so as to collapse. In other embodiments, the spacing component
1410a folds, bends, buckles, fragments, or bums away, as previously
described herein, during or after the first perforating gun 1412a
fires.
[0162] Regardless of the method for reducing the length of the
releasable spacing component 1410a, the reduced length releasable
spacing component 1410a does not block production fluids from
flowing up the well bore 120. In various embodiments where debris
of the releasable spacing component 1410a remains, such debris may
have a high permeability to allow flow therethrough, or the debris
may be circulated out of the well bore 120 by the production
fluids, or the debris may be dissolvable in the production fluids,
for example.
[0163] In an alternative embodiment, a spacing component 1410a is
not provided, and the first perforating gun 1412a has an adjustable
length. In various embodiments, the perforating gun 1412a may be
collapsible, foldable, bendable, buckleable, frangible,
dissolvable, degradable, combustible, or a combination thereof,
similar to the various embodiments of the spacing component 1410a.
Thus, the first perforating gun 1412a may be moved clear or
substantially clear of the second set of perforations 1413 by being
retrieved to the surface 105, or by being at least partially
collapsed, folded, bent, buckled, fractured, dissolved, degraded,
burned away, or a combination thereof.
[0164] After the second set of perforations 1413 is created, a
fracturing fluid may be introduced into the well bore 120 for
purposes of fracturing the formation F through the second set of
perforations 1413. In more detail, referring now to FIG. 14, the
third well bore configuration 1404 is shown in the context of a
formation F containing a zone A, a zone B, and a zone C. In
operation, the zonal isolation device 1408a may be used in a well
stimulation/fracturing operation to isolate the zone A below the
zonal isolation device 1408a. Stimulation fluid may be introduced
into the well bore 120, such as by lowering a tool into the well
bore 120 for discharging the stimulation fluid at a relatively high
pressure or by pumping the fluid directly into the well bore 120.
The stimulation fluid then passes through the perforations 1413
into the zone B, a producing zone of formation F, for stimulating
the recovery of fluids in the form of oil and gas containing
hydrocarbons. These production fluids pass from the zone B, through
the perforations 1413, and up the well bore 120 for recovery at the
surface 105, such as at a well head. As previously described, the
zonal isolation device 1408a provides a check valve function
whereby fluid flow may not pass downwardly but may pass upwardly
through the zonal isolation device 1408a. In this case, after
completion of the stimulation job, and after the pressure of the
stimulation fluid has dropped sufficiently, production fluids from
the zone A may flow upwardly through the zonal isolation device
1408a and join with the production fluids from zone B, to flow up
the well bore 120 for recovery at the surface 105, such as at the
well head.
[0165] Referring to FIG. 13D, a fourth well bore configuration 1406
is depicted in which a second zonal isolation device 1408b has been
set, and a second releasable spacing component 1410b along with a
second perforating gun 1412b have been deployed to create a third
set of perforations 1416. The fourth well bore configuration 1406
depicts the method after the second perforating gun 1412b has
created the third set of perforations 1416 in the well bore casing
1414 and the second releasable spacing component 1410b has reduced
in length. The process whereby the second zonal isolation device
1408b, the second releasable spacing component 1410b, and the
second perforating gun 1412b are deployed into the well, set and
fired may be the same as or similar to the process described above
for the first zonal isolation device 1408a, the first releasable
spacing component 1410b, and the first perforating gun 1412b.
[0166] Referring again to FIG. 14, a typical stimulation job may be
conducted to stimulate the recovery of fluids in the form of oil
and gas containing hydrocarbons through the third set of
perforations 1416 from the zone C, for example. These production
fluids pass from the zone C, through the perforations 1416, and up
the well bore 120 for recovery at the surface 105, such as at a
well head. Again, the second zonal isolation device 1408b provides
a check valve function whereby fluid flow may not pass downwardly
but may pass upwardly through the device 1408b. In this case, after
completion of the stimulation or fracturing job, and after the
pressure of the stimulation fluid has dropped sufficiently,
production fluids from zone A and zone B below the second zonal
isolation device 1408b may flow upwardly through the device 1408b
and join with the production fluids from zone C, and up the well
bore 120 for recovery at the surface 105, such as at the well
head.
[0167] Referring again to FIGS. 13, after the well fracturing
operation is complete, the various tools may be removed from the
well bore 120. In an embodiment, the first zonal isolation device
1408a, the second zonal isolation device 1408b, the first
perforating gun 1412a, and the second perforating gun 1412b may be
floated back to the surface via production fluid flow.
[0168] In an embodiment, the first zonal isolation device 1408a,
the first perforating gun 1412a, the second zonal isolation device
1408b, and the second perforating gun 1412b may be drilled through
using a drill bit and a drill string assembly.
[0169] In an embodiment, the zonal isolation devices 1408a, 1408b
may self-activate to release from the casing 1414 and descend to
the bottom of the well bore 120 by force of gravity or by pumping
using servicing fluid. Alternately, the zonal isolation devices
1408a, 1408b may fully or partially dissolve, for example in the
presence of a fluid pumped into the well bore 120 for this purpose,
such that the devices 1408a, 1408b release from the casing 1414 and
descend to the bottom of the well bore 120 by force of gravity or
by pumping using servicing fluid.
[0170] Turning now to FIGS. 15A, 15B, and 15C, a method of
self-navigating and self-activating a plurality of autonomous
perforating guns 1450a, 1450b, 1450c to create multiple sets of
perforations 1452, 1456, 1460 in a well bore casing 1446 is
depicted. Referring to FIG. 15A and to well bore configuration
1448, a first autonomous perforating gun 1450a is shown making a
first set of perforations 1452 through the casing 1446 and into the
formation F beyond.
[0171] The perforating gun 1450a is deployed into the well bore 120
via an external force, and the gun 1450a is operable to
self-determine its location within the well bore 120. In an
embodiment, the gun 1450a is deployed into the well bore by force
of gravity or by being pumped into the well bore 120 in a fluid
being circulated in the well bore 120, or both. In an embodiment,
the gun 1450a is operable to self-fire perforating charges at
predetermined locations within the well bore 120 to perforate the
well bore casing 1446. In an embodiment, as the perforating gun
1450a approaches the predetermined location for creating the first
set of perforations 1452, a braking system 760 is activated to slow
the velocity of the perforating gun 1450a. Thus, when the
perforating gun 1450a reaches the predetermined location, the
perforating gun 1450a has sufficiently slowed or stopped before it
self-fires perforating charges, thereby creating the first set of
perforations 1452. The first perforating gun 1450a may then
deactivate the brake and continue traversing the well bore 120 to
descend to the bottom thereof, or may otherwise disintegrate or be
removed from the well bore 120 by techniques described herein.
[0172] Referring now to FIG. 15B and to well bore configuration
1454, a second autonomous perforating gun 1450b is shown making a
second set of perforations 1456 through the casing 1446 and into
the formation F beyond. In an embodiment, as the second perforating
gun 1450b approaches the predetermined location for creating the
second set of perforations 1456, a braking system 760 is activated
to slow the velocity of the perforating gun 1450b. Thus, when the
perforating gun 1450b reaches the predetermined location, it has
sufficiently slowed or stopped before it self-fires perforating
charges, thereby creating the second set of perforations 1456. The
perforating gun 1450 may then deactivate the brake and continue
traversing the well bore 120 to descend to the bottom thereof, or
may otherwise disintegrate or be removed from the well bore 120 by
techniques described herein.
[0173] Referring now to FIG. 15C and to well bore configuration
1458, a third perforating gun 1450c is shown making a third set of
perforations 1460 in the casing 1446 according to the same or
similar methods employed to make the first and second sets of
perforations 1452, 1456. In various embodiments, each of the
perforating guns 1450a, 1450b, and 1450c may be disposed of, for
example, by descending to the bottom of the well bore 120, or each
of the perforating guns 1450a, 1450b, and 1450c may be retrieved to
the surface 105, such as by altering its buoyancy so that it floats
to the surface 105, for example.
[0174] Turning now to FIGS. 16A, 16B, and 16C, in an alternative
method, an autonomous downhole tool 1475 comprising a string of
perforating guns 1450a, 1450b, 1450c may be used to create multiple
sets of perforations 1452, 1456, 1460 in a well bore casing 1446.
The autonomous downhole tool 1475 is deployed into the well bore
120 via an external force, and is operable to self-determine its
location within the well bore 120. In an embodiment, the autonomous
downhole tool 1475 is deployed into the well bore 120 by force of
gravity or by being pumped into the well bore 120 in a fluid being
circulated in the well bore 120, or both. In an embodiment, the
autonomous downhole tool 1475 is operable to self-fire perforating
charges from one or more of the perforating guns 1450a, 1450b,
1450c at predetermined locations within the well bore 120 to
perforate the well bore casing 1446.
[0175] Referring to FIG. 16A and to well bore configuration 1448,
an upper perforating gun 1450a of the autonomous downhole tool 1475
is shown making a first set of perforations 1452 through the casing
1446 and into the formation F beyond. In an embodiment, as the
autonomous downhole tool 1475 approaches the predetermined location
for creating the first set of perforations 1452, a braking system
760 is activated to slow the velocity of the tool 1475. Thus, when
the upper perforating gun 1450a reaches the predetermined location,
the tool 1475 has sufficiently slowed or stopped before the upper
perforating gun 1450a self-fires perforating charges, thereby
creating the first set of perforations 1452. The braking system 760
may then be deactivated so that the autonomous downhole tool 1475
may continue traversing the well bore 120.
[0176] Referring now to FIG. 16B and to well bore configuration
1454, a middle perforating gun 1450b is shown making a second set
of perforations 1456 through the casing 1446 and into the formation
F beyond. In an embodiment, as the autonomous downhole tool 1475
approaches the predetermined location for creating the second set
of perforations 1456, a braking system 760 is activated to slow the
velocity of the tool 1475. Thus, when the middle perforating gun
1450b reaches the predetermined location, the tool 1475 has
sufficiently slowed or stopped before the middle perforating gun
1450b self-fires perforating charges, thereby creating the second
set of perforations 1456. The braking system 760 may then be
deactivated so that the autonomous downhole tool 1475 may continue
traversing the well bore 120.
[0177] Referring now to FIG. 16C and to well bore configuration
1458, a lower perforating gun 1450c is shown making a third set of
perforations 1460 in the casing 1446 according to the same or
similar methods employed to make the first and second sets of
perforations 1452, 1456. In various embodiments, the autonomous
downhole tool 1475 may be disposed of, for example, by descending
to the bottom of the well bore 120, or the tool 1475 may be
retrieved to the surface 105, such as by altering its buoyancy so
that it floats to the surface 105, for example.
[0178] The foregoing descriptions of specific embodiments of an
autonomous tool 100, 755, 1408, 1450, 1475 and the systems and
methods for servicing a well bore 120 using such tools 100, 755,
1408, 1450, 1475 have been presented for purposes of illustration
and description and are not intended to be exhaustive or to limit
the invention to the precise forms disclosed. Obviously many other
modifications and variations are possible. In particular, the type
of autonomous downhole tool, the particular components that make up
the downhole tool, or the type of well servicing method could be
varied.
[0179] While various embodiments of the invention have been shown
and described herein, modifications may be made by one skilled in
the art without departing from the spirit and the teachings of the
invention. The embodiments described here are exemplary only, and
are not intended to be limiting. Many variations, combinations, and
modifications of the invention disclosed herein are possible and
are within the scope of the invention. Accordingly, the scope of
protection is not limited by the description set out above, but is
defined by the claims which follow, that scope including all
equivalents of the subject matter of the claims.
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