U.S. patent application number 11/627156 was filed with the patent office on 2007-12-06 for method and apparatus for sensing downhole characteristics.
Invention is credited to Maximo Hernandez.
Application Number | 20070278009 11/627156 |
Document ID | / |
Family ID | 38788794 |
Filed Date | 2007-12-06 |
United States Patent
Application |
20070278009 |
Kind Code |
A1 |
Hernandez; Maximo |
December 6, 2007 |
Method and Apparatus for Sensing Downhole Characteristics
Abstract
A system for sensing a borehole or formation characteristic at a
selected depth while a drill string 12 is in the borehole 36
includes a plurality of sensors 40 to positioned at axially spaced
locations along the drill string 12, and a data transmission system
46 for transmitting signals from each of the plurality of sensors
to the surface. A surface computer 22 receives the transmitted
signals and determining the sensed characteristics at a selected
depth as a function of one of a plurality of sensors positioned
along the drill string while at a first selected depth and
subsequently another of the plurality of sensors is along the drill
string while at substantially the first selected depth.
Inventors: |
Hernandez; Maximo; (Houston,
TX) |
Correspondence
Address: |
JEFFREY E. DALY;INTELLISERV, INC
400 N. SAM HOUSTON PARKWAY EAST, SUITE 900
HOUSTON
TX
77060
US
|
Family ID: |
38788794 |
Appl. No.: |
11/627156 |
Filed: |
January 25, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60804015 |
Jun 6, 2006 |
|
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Current U.S.
Class: |
175/40 ;
175/50 |
Current CPC
Class: |
E21B 47/00 20130101 |
Class at
Publication: |
175/40 ;
175/50 |
International
Class: |
E21B 47/00 20060101
E21B047/00 |
Claims
1. A system for sensing a selected borehole or formation
characteristic at a selected depth while a drill string is in the
borehole, comprising: a plurality of sensors each positioned at
axially spaced locations along the drill string, each of the
plurality of sensors sensing the selected borehole or formation
characteristic; a data transmission system for transmitting signals
from each of the plurality of sensors to the surface; and a surface
computer for receiving the transmitted signals and determining the
sensed characteristic at a selected depth as a function of one of
the plurality of sensors positioned along the drill string while at
a first selected depth and subsequently another of the plurality of
sensors positioned along the drill string while at substantially
the first selected depth.
2. A system as defined in claim 1, wherein each of a plurality of
sensors senses a spacing to a borehole wall at a selected depth,
such that the signals from the plurality of sensors indicate a
change in spacing to the borehole wall over time.
3. A system as defined in claim 2, wherein each of a plurality of
sensors measures a caliper of the borehole.
4. A system as defined in claim 1, further comprising: a surface
display for displaying signals from the plurality of sensors.
5. A system as defined in claim 1, wherein signals from each of a
plurality of sensors transmitted to the surface computer by a wire
conductor spaced along the drill string.
6. A system as defined in claim 5, wherein the transmission system
includes: a plurality of nodes spaced along the drill string and
interfacing with each of a plurality of sensors; and a plurality of
communication links between the nodes.
7. A system as defined in claim 1, wherein the computer
distinguishes signals from the plurality of sensors as a function
of their spacing along the drill string.
8. A system as defined in claim 1, wherein the sensed
characteristic are displayed at the surface as a function of
depth.
9. A system as defined in claim 1, wherein at least one of the
plurality of sensors is positioned on a bottom hole assembly.
10. A system as defined in claim 9, wherein at least one of the
plurality of sensors is positioned on a bit.
11. A method of sensing a selected borehole or formation
characteristic at a selected depth while a drill string is in the
borehole, comprising: positioning each of a plurality of sensors at
axially spaced locations along the drill string; sensing the
selected borehole or formation characteristic with each of the
plurality of sensors; transmitting signals from each of the
plurality of sensors to the surface; receiving the transmitted
signals and determining the sensed characteristic at a selected
depth as a function of one of the plurality of sensors positioned
along the drill string while at a first selected depth and
subsequently another of the plurality of sensors positioned along
the drill string while at subsequently the first selected
depth.
12. A method as defined in claim 11, wherein each of a plurality of
sensors senses a spacing to a borehole wall at a selected depth,
such that the signals from the plurality of sensors indicate a
change in spacing to the borehole wall over time.
13. A method as defined in claim 12, wherein each of a plurality of
sensors measures a caliper of the borehole.
14. A method as defined in claim 11, further comprising: displaying
signals from the plurality of sensors at the surface in
substantially real time.
15. A method as defined in claim 14, further comprising: displaying
a rate of change in the transmitted signals.
16. A method as defined in claim 11, wherein signals from each of
the plurality of sensors are transmitted to the computer through a
wire conductor along the drill string.
17. A method as defined in claim 15, wherein a signal transmission
system includes: a plurality of nodes spaced along the drill string
and interfacing with each of the plurality of sensors; and a
plurality of communication links between the nodes.
18. A method as defined in claim 11, wherein a computer
distinguishes signals from the plurality of sensors as a function
of their spacing along the drill string.
19. The method as defined in claim 11, wherein the sensed
characteristics are displayed at the surface as a function of the
depth.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a non-provisional application claiming
priority from U.S. provisional application Ser. No. 60/804,015,
filed on Jun. 6, 2006--the entire disclosure of which is
incorporated by reference herein for all it contains.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention pertains to well drilling operations
and, more particularly, to sensing a change in downhole conditions
over time and depth while a drill string is in the well.
[0004] 2. Description of the Related Art
[0005] Drilling operators logically need as much information as
possible about borehole and formation characteristics while
drilling a well for safety and reserves calculations. If problems
arise while drilling, minor interruptions may be expensive to
overcome and, in some cases, pose a safety risk. Since current
economic conditions provide little margin for error and cost,
drilling operators have a strong incentive to fully understand
downhole characteristics and avoid interruptions.
[0006] Gathering information from downhole can be challenging,
particularly since the downhole environment is harsh, ever
changing, and any downhole sensing system is subject to high
temperature, shock, and vibration. In many wells, the depth of the
well at which the sensors are positioned causes significant
attenuation in the signals which are transmitted to the surface. If
signals are lost or data becomes corrupted during transmission, the
operator's reliance on that data may result in significant
problems. Accordingly, many downhole conditions sensed while
drilling a well have reliability concerns.
[0007] Typically, various types of sensors may be placed at a
selected location along the bottom end of the drill string, and a
mud pulser, which is part of a measurement-while-drilling (MWD)
system is widely used in the oilfield industry to transmit and send
signals to the surface. Signals from bottom hole sensors may be
transmitted to the surface from various depths, but sensed
conditions at a particular depth near the wellbore are generally
assumed to remain substantially the same as when initially sensed.
In many applications, this assumption is erroneous, and downhole
sensed conditions at a selected depth change over time. In other
applications, a downhole condition may not have changed, but the
error rate in the transmitted signals does not provide high
reliability that the sensed conditions are accurately determined.
Updated sensed conditions are typically not available to the
drilling operator, and accordingly most drilling operations
unnecessarily incur higher risks and costs than necessary. The
disadvantages of the prior art are overcome by the present
invention, and an improved method and system for sensing a selected
borehole or formation characteristic in a well is disclosed.
BRIEF SUMMARY OF THE INVENTION
[0008] In one embodiment, a system for sensing a borehole or
formation characteristic at a selected depth includes a plurality
of sensors each positioned at axially spaced locations along a
drill string, with each of the plurality of sensors sensing the
selected borehole or formation characteristic. A data transmission
system is utilized for transmitting signals from each of a
plurality of sensors to the surface. A surface computer receives
the transmitted signals and determines sensed characteristics at a
selected depth as a function of one of the plurality of sensors
positioned along a drill string while at a selected first depth,
and subsequently another of the plurality of sensors positioned
along the drill string while at substantially the first selected
depth.
[0009] According to another embodiment, a method of sensing a
selected borehole or formation characteristic depth includes
positioning each of a plurality of sensors at axially spaced
locations along a drill string, sensing the selected borehole
formation characteristic with each of a plurality of sensors,
transmitting signals from each of a plurality of sensors to the
surface, and receiving the transmitted signals and determining a
sensed characteristic at a selected depth as a function of one of
the plurality of sensors positioned along the drill string while at
a first selected depth, and subsequently another of the plurality
of sensors positioned along the drill string while at substantially
the first selected depth.
[0010] These and further features and advantages of the present
invention will become apparent from the following detailed
description, wherein reference is made to the figures in the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a cross-sectional view illustrating one embodiment
of a drill rig showing a directional drilling application and a
system for sensing borehole or formation characteristics.
[0012] FIG. 2 is a functional block diagram of a suitable data
transmission from the plurality of sensors.
[0013] FIG. 3 is a representative plot for analyzing measurements
at the same depths for changes over time.
DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED
EMBODIMENT
[0014] FIG. 1 illustrates a drilling operation 10 in which a
borehole 36 is being drilled beneath the surface 26 of the ground.
The drilling operation includes a drilling rig 20 and a drill
string 12 which extends from the rig into the borehole. A bit or
other cutting device 16 is provided at the lower end of the drill
string. The bottom hole assembly 15 may include a drill bit 16, a
new bit sensor package 38 and a directional drilling motor or
rotary steerable device 14, as shown in FIG. 1.
[0015] The drill string 12 preferably includes a plurality of
network nodes 30. The nodes 30 are provided at desired intervals
along the drill string. Network nodes essentially function as
signal repeaters to regenerate data signals and mitigate signal
attenuation as data is transmitted up and down the drill string.
The nodes 30 may be integrated into an existing section of drill
pipe or a downhole tool along the drill string. Sensor package 38
in the bottom hole assembly may also include a network node 30.
Connectors 34 represent drill pipe joint connectors, while the
connectors 32 connect a node 30 to an upper and lower drill pipe
joint.
[0016] The nodes 30 comprise a portion of a downhole network 46
used to transmit information along the drill string. A downhole
network may thus include multiple nodes based along the drill
string. Communication links 48 may be used to connect the nodes to
one another, and may comprise cables or other transmission media
integrated directly into sections of the drill string. The cable
may be routed through the central borehole of the drill string, or
routed externally to the drill string, or mounted within a groove,
slot or passageway in the drill string. Preferably signals from the
plurality of sensors are transmitted to the surface through a wire
conductor 48 along the drill string. Communication links may also
use wireless connections.
[0017] A plurality of packets may be used to transmit information
along the nodes. Packets may be used to carry data from tools or
sensors located downhole to an uphole mode, or may carry
information or data necessary to function the network. Other
packets may be used to send control signals from the top node to
tools or sensors located at various downhole positions. Further
detail with respect to suitable nodes, a network, and data packets
are disclosed in U.S. Publication 2005/0284663 A1 hereby
incorporated by reference.
[0018] Various types of sensors may be employed along the drill
string, including axially spaced resistivity, caliper, rock
strength (sonic), pressure sensors, temperature sensors, seismic
devices, strain gauges, inclinometers, accelerometers, bending,
vibration, and rotation sensors, and flow rate sensors. Sensors
which measure conditions which would logically experience
significant change over time provide particularly valuable
information to the drilling operator. For example, the caliper or
cross-sectional configuration of a wellbore at a particular depth
may change during the drilling operation due to formation stability
and fluid washout conditions. The skin of a formation defining the
borehole may tend to absorb fluids in the well and may thus also
change over time, particularly if the well is overbalanced. By
providing a system which allows a sensor to transmit to the surface
at a known depth in substantially real time, a particular borehole
or formation characteristic, such as the caliper of the well, and
by providing another sensor which can provide the same type of
information at substantially the same depth with a different sensor
as the well is drilled deeper, the operator is able to compare a
wellbore caliper profile at a selected depth at time one, and later
measure the same caliper at substantially the same depth at time
two. This allows the operator to better understand changes in the
well that occur over time, and to take action which will mitigate
undesirable changes. Other sensors which monitor conditions which
are likely to degrade or change over time include sensors that
measure wellbore stability, resistivity sensors, equivalent
circulating density (ECD) measurements sensors, primary and/or
secondary porosity sensors, and temperature sensors.
[0019] Other sensors may monitor conditions which are unlikely to
substantially change over time, such as borehole inclination, pore
pressure sensors, and other sensors measuring petrophysical
properties of the formation or of the fluid in the formation. In
the latter case, an operator may use the signals from different
sensors at different times to make a better determination of the
actual condition sensed. For example, the inclination of a wellbore
at a particular depth likely will not change. The inclination
measurement at time one may thus be averaged with an inclination at
the same depth at time two and another inclination measurement at
the same depth at time three, so that the average of these three
signals at the same depth taken at three times will likely provide
a more accurate indication of the actual borehole inclination.
[0020] According to the technique of the present invention, an
operator at the surface may instruct a particular sensor to take a
selected measurement. In most applications, however, a plurality of
substantially identical sensors for sensing a particular wellbore
formation characteristic will be provided along the drill string,
and each of those sensors will output a signal at a selected time
interval, e.g., every tenth of a second or every second, such that
signals at any depth may be correlated with signals from a similar
sensor at another depth. Thus an entire profile of the sensed
condition based on a first sensor as a function of depth may be
plotted by the computer, and a time lapse plot may be depicted for
measurements from a second sensor while at the same depth at a
later time. Also, it should be understood that the system may
utilize sensors which are able to take reliable readings while the
drill string and thus the sensors are rotating in the well, but in
another application the rotation of the drill string may be briefly
interrupted so that sensed conditions can be obtained from
stationary sensors, then drilling resumed. In still other cases,
the drill string may slide or rotate slowly in the well while the
sensed conditions are monitored, with the majority of the power to
the bit being provided by the downhole motor or rotary steerable
device.
[0021] A significant advantage of the present invention is the
ability to analyze information from the sensors when there is time
lapse between a particular sensed condition at a particular depth,
and the subsequent same sensed condition at the same depth. As
disclosed herein, the system provides sensors for sensing
characteristics at a selected depth in a well, and a particular
depth may be "selected" in that the operator is particularly
concerned with signals at that depth, and particularly change and
rate of change for certain characteristics. Such change and rate of
change (time lapse in the transmitted signals) may be displayed to
the operator in real time). Otherwise stated, however, information
from a sensor at selected axial locations or after a selected time
lapse may be important, and the term "selected" as used herein
would include a signal at any known, presumed, or selected
depth.
[0022] FIG. 2 illustrates conceptually a drill pipe 12 having a
plurality of axially spaced sensors 40 spaced along the drill
string, each for sensing the same borehole or formation
characteristic. Each sensor may be provided within one of the nodes
30 positioned along the drill string, as previously discussed. The
downhole network 46 transmits information from each of a plurality
of sensors to surface computer 22, which also receives information
from depth sensor 50 via line 51. Depth sensor 50 monitors the
length of drill string inserted in the well, and thus the output
from the sensors 14 may be correlated by the computer 22 as a
function of their depth in the well.
[0023] Information from the well site computer 22 may be displayed
for the drilling operator on a well site screen 24. Information may
also be transmitted from computer 22 to another computer 23,
located at a site remote from the well, with this computer 23
allowing an individual in the office remote from the well to review
the data output by the sensors 40. Although only five sensors 40
are shown in FIG. 1, those skilled in the art will understand that
a larger number of sensors may be used along a drill string when
drilling a fairly deep well, and that all sensors associated with
any particular node may be housed within or annexed to the node 30,
so that a variety of sensors rather than a single sensor will be
associated with that particular node.
[0024] FIG. 3 depicts a plot of sensed borehole information
characteristics numbered 1 and 2 each plotted as a function of
depth, and also plotted as a function of time when the measurements
are taken. For characteristic #1, pass 1 occurs first, pass 2
occurs later, and pass 3 occurs after pass 2. The area represented
by 60 shows the difference in measurements between passes 1 and 2,
while the area represented by 62 represents a difference in
measurements between passes 2 and 3. The strong signal at depth D1
for the first pass is thus new and is further reduced for pass 2
and pass 3. For characteristic #2, the area 64 represents the
difference between the pass 1 signal and the pass 2 signal, and the
area 66 represents the difference between the pass 2 and pass 3
signals. For this borehole information characteristic, signal
strength increases between pass 1 and 2, and further increases
between pass 2 and 3.
[0025] Those skilled in the art will appreciate that various forms
of markings may be employed to differentiate a first pass from a
second pass, and a second pass from a subsequent pass, and that
viewing the area difference under the curve of signals from
different passes is only one way of determining the desired
characteristic of the borehole or formation. Assuming that
characteristic #2 is the borehole size, the operator may thus
assume that, at a depth shortly above depth D1, the borehole has
increased in size, and has again increased in size between the
taking of the pass 2 measurements and the pass 3 measurements. For
all of the displayed signals, signals may be displayed as a
function of plurality of sensors at a single elected location in a
borehole, so that a sent signal at a depth of, e.g., 1550 feet,
will be compared with a similar signal from a similar sensor
subsequently at a depth of 1550 feet.
[0026] Although specific embodiments of the invention have been
described herein in some detail, this has been done solely for the
purposes of explaining the various aspects of the invention, and is
not intended to limit the scope of the invention as defined in the
claims which follow. Those skilled in the art will understand that
the embodiment shown and described is exemplary, and various other
substitutions, alterations and modifications, including but not
limited to those design alternatives specifically discussed herein,
may be made in the practice of the invention without departing from
its scope.
[0027] Whereas the present invention has been described in
particular relation to the drawings attached hereto, it should be
understood that other and further modifications apart from those
shown or suggested herein, may be made within the scope and spirit
of the present invention.
* * * * *