U.S. patent application number 11/510114 was filed with the patent office on 2008-02-28 for wellbore tractor with fluid conduit sheath.
Invention is credited to N. Bruce Moore.
Application Number | 20080047715 11/510114 |
Document ID | / |
Family ID | 38608876 |
Filed Date | 2008-02-28 |
United States Patent
Application |
20080047715 |
Kind Code |
A1 |
Moore; N. Bruce |
February 28, 2008 |
Wellbore tractor with fluid conduit sheath
Abstract
A fluid conduit sheath for a wellbore tractor can provide
transportation of a working fluid external to a wellbore tractor in
a downhole environment. The fluid conduit sheath can further
provide cooling to electrical devices in the wellbore tractor. The
fluid conduit sheath can be configured to be disposed around the
body of the wellbore tractor, defining a fluid conduit between the
sheath and the wellbore tractor. Spacers can be used to maintain
the position of the sheath relative to the tractor and also to
couple the tractor to the sheath. The fluid conduit sheath can be
advantageous in tractors whose internal components substantially
preclude the use of an internal fluid conduit, such as tractors
with electrically-actuated grippers.
Inventors: |
Moore; N. Bruce; (Aliso
Viejo, CA) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
38608876 |
Appl. No.: |
11/510114 |
Filed: |
August 24, 2006 |
Current U.S.
Class: |
166/381 ;
166/162 |
Current CPC
Class: |
E21B 23/001 20200501;
E21B 4/18 20130101 |
Class at
Publication: |
166/381 ;
166/162 |
International
Class: |
E21B 23/00 20060101
E21B023/00 |
Claims
1. A tool for moving within a passage, comprising: an elongate body
having an outer surface; at least one gripper assembly engaged with
the body, the gripper assembly having an actuated position in which
the gripper assembly grips onto an inner surface of the passage to
substantially limit relative movement between the gripper assembly
and the inner surface, the gripper assembly having a retracted
position in which the gripper assembly permits substantially free
relative movement between the gripper assembly and the inner
surface of the passage; an actuator configured to move the gripper
between the actuated position and the retracted position; and a
fluid conduit sheath disposed around at least a portion of the
elongate body and having an inner surface such that the fluid
conduit sheath defines a fluid conduit between the outer surface of
the elongate body and the inner surface of the fluid conduit
sheath.
2. The tool of claim 1, wherein the elongate body has a
circumference and the fluid conduit sheath comprises: a first
segment defined by a substantially cylindrical profile disposed
around substantially the entire circumference of the elongate body;
and a second segment configured to allow passage of the gripper
assembly therethrough when the gripper assembly is in the actuated
position.
3. The tool of claim 1, further comprising a spacer separating the
outer surface of the elongate body and the inner surface of the
fluid conduit sheath.
4. The tool of claim 1, further comprising a plurality of spacers
separating the outer surface of the elongate body and the inner
surface of the fluid conduit sheath.
5. The tool of claim 1, wherein the actuator comprises a motor
configured to be powered by electricity.
6. The tool of claim 5, wherein the fluid conduit sheath is
configured to direct fluid near the motor to cool the motor.
7. The tool of claim 1, further comprising coiled tubing.
8. A sheath for use with a tool for moving within a passage, the
sheath comprising: a sheath body having an inner surface, the
sheath body configured to be disposed around the tool such that the
sheath body defines a fluid conduit between an outer surface of the
tool and the inner surface of the sheath body; and at least one
spacer configured to separate the tool and the sheath body to
maintain the position of the tool with respect to the sheath
body.
9. The sheath of claim 8, wherein the tool comprises an elongate
body and a gripper assembly, the gripper assembly having an
actuated position in which the gripper assembly grips onto an inner
surface of the passage to substantially limit relative movement
between the gripper assembly and the inner surface, the gripper
assembly having a retracted position in which the gripper assembly
permits substantially free relative movement between the gripper
assembly and the inner surface of the passage; and wherein the
sheath body comprises: a first portion configured to be disposed
around the elongate body; and a second portion configured to allow
passage of the gripper assembly therethrough when the gripper
assembly is in the actuated position.
10. The sheath of claim 9, wherein the gripper assembly comprises
three gripper arms and wherein the second portion of the sheath
body comprises three apertures, the apertures sealed with respect
to the tool such that fluid is retained in the fluid conduit, and
each of the apertures configured to permit passage of a
corresponding gripper arm therethrough when the gripper assembly is
in the actuated position.
11. The sheath of claim 9, wherein the sheath is comprised of a
material selected to withstand elevated temperatures in the
passage.
12. A method of transporting fluid downhole in a tool for moving
within a passage, the method comprising: providing a tool for
moving within a passage, the tool comprising: an elongate body
having an outer surface; at least one gripper assembly engaged with
the body, the gripper assembly having an actuated position in which
the gripper assembly grips onto an inner surface of the passage to
substantially limit relative movement between the gripper assembly
and the inner surface, the gripper assembly having a retracted
position in which the gripper assembly permits substantially free
relative movement between the gripper assembly and the inner
surface of the passage; a fluid conduit sheath disposed around at
least a portion of the elongate body and having an inner surface
such that the fluid conduit sheath defines a fluid conduit between
the outer surface of the elongate body and the inner surface of the
fluid conduit sheath and; transporting fluid through the fluid
conduit external to the elongate body.
13. The method of claim 12, wherein the tool further comprises an
electrical component and wherein the fluid conduit sheath is
configured to direct fluid near the electrical component to cool
the electrical component.
14. The method of claim 13, wherein the electrical component
comprises an electric motor configured to cause the gripper
assembly to move between its actuated position and its retracted
position.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This application relates generally to downhole tools and
more specifically to devices, systems, and methods for transporting
fluids in connection with downhole tools.
[0003] 2. Description of the Related Art
[0004] Tractors for moving within underground boreholes are used
for a variety of purposes, such as oil drilling, mining, laying
communication lines, and many other purposes. In the petroleum
industry, for example, a typical oil well comprises a vertical
borehole that is drilled by a rotary drill bit attached to the end
of a drill string. The drill string may be constructed of a series
of connected links of drill pipe that extend between ground surface
equipment and the aft end of the tractor. Alternatively, the drill
string may comprise flexible tubing or "coiled tubing" connected to
the aft end of the tractor. A drilling fluid, such as drilling mud,
is pumped from the ground surface equipment through an interior
flow channel of the drill string and through the tractor to the
drill bit. The drilling fluid is used to cool and lubricate the
bit, and to remove debris and rock chips from the borehole, which
are created by the drilling process. The drilling fluid returns to
the surface, carrying the cuttings and debris, through the annular
space between the outer surface of the drill pipe and the inner
surface of the borehole.
[0005] Tractors for moving within downhole passages are often
required to operate in harsh environments and limited space. For
example, tractors used for oil drilling may encounter hydrostatic
pressures as high as 16,000 psi and temperatures as high as
300.degree. F. Typical boreholes for oil drilling are 3.5-27.5
inches in diameter. Further, to permit turning, the tractor length
should be limited. Also, tractors must often have the capability to
generate and exert substantial force against a formation. For
example, operations such as drilling require thrust forces as high
as 30,000 pounds.
[0006] As a result of the harsh working environment, space
constraints, and desired force generation requirements, downhole
tractors are used only in very limited situations, such as within
existing well bore casing. While a number of the inventors of this
application have previously developed a significantly improved
design for a downhole tractor, further improvements are desirable
to achieve performance levels that would permit downhole tractors
to achieve commercial success in other environments, such as open
bore drilling.
[0007] Western Well Tool, Incorporated has developed a variety of
downhole tractors for drilling, completion and intervention
processes for wells and boreholes. For example, the Puller-Thruster
Tractor is a multi-purpose tractor (U.S. Pat. Nos. 6,003,606,
6,286,592, and 6,601,652) that can be used in rotary, coiled tubing
and wireline operations. A method of moving is described in U.S.
Pat. No. 6,230,813. The Electro-hydraulically Controlled Tractor
(U.S. Pat. Nos. 6,241,031 and 6,427,786) defines a tractor that
utilizes both electrical and hydraulic control methods. The
Electrically Sequenced Tractor (U.S. Pat. No. 6,347,674) defines a
sophisticated electrically controlled tractor. The Intervention
Tractor (also called the Tractor with improved valve system, U.S.
Pat. No. 6,679,341 and U.S. Patent Application Publication No.
2004/0168828) is preferably an all hydraulic tractor intended for
use with coiled tubing that provides locomotion downhole to deliver
heavy loads such as perforation guns and sand washing. A tractor
using an Expandable Ramp Gripper, which can incorporate the use of
a plurality of interconnected links to produce a dual radial force
mechanism is described in U.S. Provisional Patent Application No.
60/781,885. Each of the foregoing patents and patent applications
is incorporated by reference herein in its entirety.
[0008] These various tractors are intended to provide locomotion,
to pull or push various types of loads. For each of these various
types of tractors, various types of gripper elements have been
developed. Thus an important part of the downhole tractor tool is
its gripper system.
[0009] In one known design, a tractor comprises an elongated body,
a propulsion system for applying thrust to the body, and grippers
for anchoring the tractor to the inner surface of a borehole or
passage while such thrust is applied to the body. Each gripper has
an actuated position in which the gripper substantially prevents
relative movement between the gripper and the inner surface of the
passage, and a retracted position in which the gripper permits
substantially free relative movement between the gripper and the
inner surface of the passage. Typically, each gripper is slidingly
engaged with the tractor body so that the body can be thrust
longitudinally while the gripper is actuated. The grippers
preferably do not substantially impede "flow-by," the flow of fluid
returning from the drill bit up to the ground surface through the
annulus between the tractor and the borehole surface.
[0010] Tractors may have at least two grippers that alternately
actuate and reset to assist the motion of the tractor. In one cycle
of operation, the body is thrust longitudinally along a first
stroke length while a first gripper is actuated and a second
gripper is retracted. During the first stroke length, the second
gripper moves along the tractor body in a reset motion. Then, the
second gripper is actuated and the first gripper is subsequently
retracted. The body is thrust longitudinally along a second stroke
length. During the second stroke length, the first gripper moves
along the tractor body in a reset motion. The first gripper is then
actuated and the second gripper subsequently retracted. The cycle
then repeats. Alternatively, a tractor may be equipped with only a
single gripper for specialized applications of well intervention,
such as movement of sliding sleeves or perforation equipment.
[0011] Grippers may be designed to be powered by fluid, such as
drilling mud in an open tractor system or hydraulic fluid in a
closed tractor system. Typically, a gripper assembly has an
actuation fluid chamber that receives pressurized fluid to cause
the gripper to move to its actuated position. The gripper assembly
may also have a retraction fluid chamber that receives pressurized
fluid to cause the gripper to move to its retracted position.
Alternatively, the gripper assembly may have a mechanical
retraction element, such as a coil spring or leaf spring, which
biases the gripper back to its retracted position when the
pressurized fluid is discharged. Motor-operated or hydraulically
controlled valves in the tractor body can control the delivery of
fluid to the various chambers of the gripper assembly.
[0012] In other tractor configurations, grippers are designed to be
actuated by electric motors. The electric motors operate by
rotating an output shaft coupled to the gripper to move the gripper
between its retracted position and its actuated position. Often,
tractors including electric motors include other electronic
components, such as processor-based control systems to control the
sequenced operation of the grippers described above. The electric
motors and components must be configured to withstand the high
temperatures and pressures often encountered in downhole
environments.
[0013] In addition to the drilling fluid or hydraulic fluid noted
above, various downhole operations can require a supply of working
fluid. For example, sand working, equipment manipulation, setting
patches, milling, logging and perforating, and displacing fluid or
slurry are typically performed with a working fluid. This working
fluid must be transported downhole. In tractors with fluid powered
grippers, the fluid used for gripper actuation can be used in
downhole operations in addition to powering the grippers. However,
tractors having electrically actuated grippers often lack the
ability to transport fluid for use in downhole operations.
SUMMARY OF THE INVENTION
[0014] In various embodiments, a tractor including a fluid conduit
sheath, a fluid conduit sheath, and a method for transporting fluid
are provided. The embodiments discussed herein overcome the
shortcomings of prior tractors and provide transportation of a
working fluid downhole for use in downhole operations. This
external fluid conduit for transportation of working fluid downhole
can be integrated into an existing tractor, such as one having
electrically-actuated grippers. This working fluid can also be used
to cool electric motors and other electronic components of a
tractor.
[0015] In some embodiments, a tool for moving within a passage is
provided. The tool comprises: an elongate body having an outer
surface; at least one gripper assembly engaged with the body; an
actuator; and a fluid conduit sheath disposed around at least a
portion of the elongate body. The gripper assembly has an actuated
position in which the gripper assembly grips onto an inner surface
of the passage to substantially limit relative movement between the
gripper assembly and the inner surface. The gripper assembly has a
retracted position in which the gripper assembly permits
substantially free relative movement between the gripper assembly
and the inner surface of the passage. The actuator is configured to
move the gripper between the actuated position and the retracted
position. The fluid conduit sheath has an inner surface such that
the fluid conduit sheath defines a fluid conduit between the outer
surface of the elongate body and the inner surface of the fluid
conduit sheath.
[0016] In other embodiments, a sheath for use with a tool for
moving within a passage is provided. The sheath comprises a sheath
body and at least one spacer configured to separate the tool and
the sheath body. The sheath body has an inner surface. The sheath
body is configured to be disposed around the tool such that the
sheath body defines a fluid conduit between an outer surface of the
tool and the inner surface of the sheath body. The spacer is
configured to maintain the position of the tool with respect to the
sheath body.
[0017] In other embodiments, a method of transporting fluid
downhole in a tool for moving within a passage is provided. The
method comprises providing a tool for moving within a passage, the
tool comprising a fluid conduit sheath defining a fluid conduit;
and transporting fluid through the fluid conduit. The tool
comprises: an elongate body having an outer surface; at least one
gripper assembly; and the fluid conduit sheath. The gripper
assembly is engaged with the body. The gripper assembly has an
actuated position in which the gripper assembly grips onto an inner
surface of the passage to substantially limit relative movement
between the gripper assembly and the inner surface. The gripper
assembly has a retracted position in which the gripper assembly
permits substantially free relative movement between the gripper
assembly and the inner surface of the passage. The fluid conduit
sheath is disposed around at least a portion of the elongate body.
The fluid conduit sheath has an inner surface such that the fluid
conduit sheath defines a fluid conduit between the outer surface of
the elongate body and the inner surface of the fluid conduit
sheath.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a perspective view of one embodiment of tool for
movement within a passage having a fluid conduit sheath;
[0019] FIG. 2 is a schematic diagram of a longitudinal cross
section of the tool of FIG. 1;
[0020] FIG. 3 is a cross sectional view of the tool of FIG. 1 taken
along line 3-3;
[0021] FIG. 4 is a cross-sectional view of the tool of FIG. 1 taken
along line 4-4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] With reference to FIGS. 1 and 2, one embodiment of tool for
movement within a passage is shown. The tool can be a downhole
tractor 10 having an elongate body 12 and at least one gripper
assembly 14. In the illustrated embodiment, the downhole tractor 10
includes two gripper assemblies 14. It is contemplated that in
other embodiments, the tool can comprise more than two gripper
assemblies 14. The tool further comprises an actuator 16
operatively coupled to at least one of the gripper assemblies 14.
In the illustrated embodiment, each gripper assembly 14 is
operatively coupled to a corresponding one actuator 16. It is
contemplated that in other embodiments, a single actuator 16 can be
coupled to more than one gripper assembly 14. The tool further
comprises a fluid conduit sheath 18 disposed around at least a
portion of the elongate body 12.
[0023] In the illustrated embodiment, the fluid conduit sheath 18
has an inner surface 20. The fluid conduit sheath 18 defines a
fluid conduit 22 between an outer surface 24 of the elongate body
12 and the inner surface 20 of the fluid conduit sheath. A working
fluid such as a hydraulic fluid or other fluid for sand washing,
setting patches, sampling fluids, milling, logging and perforating,
or fluid and slurry displacement can be transported through the
fluid conduit 22. A pump or other fluid transport device can be
used to transport the working fluid in the fluid conduit. In some
embodiments, the fluid transport device can be positioned in the
tractor 10, while in other embodiments, the fluid transport device
can be located on the outside of the wellbore.
[0024] In the embodiments illustrated in FIGS. 1 and 2, the fluid
conduit sheath 18 comprises a generally cylindrical sheath body 26
having a generally circular cross sectional profile that is
disposed around a generally cylindrical elongate body 12 of the
downhole tool. In other embodiments, it is contemplated that the
sheath body 26 could have different cross-sectional configurations,
for example, the sheath body could having a generally oval cross
sectional profile, a generally triangular cross-sectional profile,
a generally square cross-sectional profile, or another shape. In
some embodiments, the shape of the sheath body 26 can be selected
to fit within or travel easily within a wellbore having a known
geometry.
[0025] Desirably, the material of the sheath body 26 is selected
and sized to withstand the adverse temperature and pressure
conditions that can be encountered by a tractor in a downhole
environment. Uphole of the tractor body, the sheath body 26 can be
a different material such as a semi rigid material allowing the
tractor to advance around bends or other obstacles substantially
without the sheath body 26 binding (as is possible with a rigid
sheath body) or crimping (as is possible with a flexible sheath
body). Uphole of the tractor body, wireline, coiled tubing 27,
other control cables, wires, tethers, or other devices can run
inside the sheath body 26 to operatively couple the tractor 10 to a
surface location.
[0026] With reference to FIGS. 3 and 4, the sheath body 26 can be
configured to allow passage of the gripper assembly 14 therethrough
when the gripper assembly is in an actuated configuration. As
illustrated in FIG. 3, the sheath body 26 comprises a first segment
30 defined by a substantially cylindrical profile configured to be
disposed around substantially the entire circumference of the
elongate body 12. As noted above, in other embodiments, the
cross-sectional profile of the first segment can be other than
circular. The external fluid conduit 22 thus allows a working fluid
to be delivered by a tractor 10 whose internal space constraints
would substantially preclude transport of fluid internally.
[0027] With reference to FIG. 4, the sheath body 26 further
comprises a second segment 32 configured to allow passage of the
gripper assembly 14 when the gripper assembly 14 is in its actuated
position. In the illustrated embodiments, a gripper assembly 14
comprises three gripper arms 28. As illustrated, the second segment
32 of the sheath body 26 comprises three apertures 34, each sized
and configured to allow the passage of a corresponding gripper arm
28. In the second segment, the fluid conduit 22 defined by the
sheath body 26 is thus divided by the apertures 34 into three flow
areas extending between each pair of adjacent gripper arms 28. Each
of the flow areas can have a pair of side walls to sealingly couple
the fluid conduit sheath 18 to the tractor 10 such that the working
fluid is retained in the fluid conduit 22. It is contemplated that
in different embodiments of tractor, gripper assemblies 14 can have
more or fewer than three gripper arms 28 and the fluid conduit
sheath 18 can have correspondingly more or fewer apertures 34 and
flow areas.
[0028] In the illustrated embodiments, the gripper assemblies 14
include linkage based gripper arms 28, however, it is contemplated
that in other embodiments, the tractor can have different gripper
configurations, such as continuous beam grippers or inflatable
bladder grippers. In these embodiments, the second segment 32 of
the fluid conduit sheath can have apertures 34 sized and configured
to allow the gripper assemblies to be actuated.
[0029] With reference to FIG. 3, the tractor can include one or
more spacers 36 separating the outer surface of the elongate body
12 from the inner surface of the fluid conduit sheath 16. The
spacers 36 can maintain the position of the fluid conduit sheath 18
relative to the elongate body of the tractor 10 such that the fluid
conduit defined thereby has a substantially constant area. The
spacers 36 can also couple the fluid conduit sheath 18 to the
tractor 10. In the illustrated embodiments, the spacers 36 maintain
the fluid conduit sheath substantially concentrically disposed
about the tractor 10, although in other embodiments, it is
contemplated that the spacers 36 can be configured to position the
fluid conduit sheath 18 such that a longitudinal axis of the fluid
conduit sheath 18 is offset from a longitudinal axis of the tractor
10.
[0030] With reference to FIG. 2, the actuator 16 for the gripper
assembly 14 may be an electric motor positioned within the elongate
body 12. In the illustrated embodiment, the electric motor drives
an output shaft which is operatively coupled to the gripper
assembly 14. It is contemplated that in other embodiments, the
actuator can be a hydraulic piston or fluid turbine actuator. In
some embodiments, the tractor 10 can include other electrical
devices, such as processor devices to control valve sequencing or
motor operations. In view of elevated temperatures that can be
encountered by the tractor 10 in a downhole environment, these
electrical motors and devices can become damaged and unreliable
after relatively short downhole operational time, requiring
maintenance or replacement. This overheating of electrical
components can be especially pronounced in tractors having electric
motor actuators as they often do not include potentially heat
dissipating internal fluid conduits to transport fluid for use in
hydraulic actuators. Advantageously, however, the flow of fluid
through the fluid conduit defined by the fluid conduit sheath 18
can cool these electrical motors and components. In some
embodiments, the fluid conduit sheath 18 can be sized and
configured such that the fluid conduit can transport a desired
volumetric flow rate of working fluid to provide a predetermined
amount of cooling for electrical components. In some embodiments,
the spacers 36 can be shaped and positioned to direct a flow of
working fluid in the fluid conduit towards electrical devices.
Thus, transport of the working fluid within the fluid conduit
sheath can extend the duty cycles of various electrical devices in
a tractor 10.
[0031] While the illustrated embodiments depict a tractor 10
including a fluid conduit sheath 18, in other embodiments, a fluid
conduit sheath 18 can be applied as a retrofit to a tractor. The
fluid conduit sheath 18 can be configured to be disposed around
existing and future tractor and gripper configurations of
Schlumberger, Welltec, Expro Americas, Inc., Aker Kvaerner, or
other downhole tractor designers and manufacturers. The cooling and
fluid transport advantages can be highly desirable on tractors
including centrally mounted electrical motors or turbines that
would substantially prevent fluid flow through an internal conduit.
However, the fluid conduit sheath can also be used in a tractor
having hydraulically actuated gripper assemblies. In these
tractors, the addition of a fluid conduit sheath as described
herein can provide fluid transportation to perform various downhole
operations, and increase equipment lifespan through cooling.
[0032] A tractor and fluid conduit sheath such as the one described
herein can be used in various embodiments of a method to
transporting fluid downhole. The method can include the steps of
providing a tractor including an elongate body, a gripper, and a
fluid conduit sheath disposed around the elongate body and defining
a fluid conduit therebetween, and transporting fluid through the
fluid conduit external to the elongate body. In some embodiments,
the method can include the steps of determining a cooling
requirement for an electrical device, and configuring the fluid
conduit sheath to have sufficient cooling capacity to meet the
cooling requirement.
[0033] Although these inventions have been disclosed in the context
of certain preferred embodiments and examples, it will be
understood by those skilled in the art that the present inventions
extend beyond the specifically disclosed embodiments to other
alternative embodiments and/or uses of the inventions and obvious
modifications and equivalents thereof. Further, the various
features of these inventions can be used alone, or in combination
with other features of these inventions other than as expressly
described above. Thus, it is intended that the scope of the present
inventions herein disclosed should not be limited by the particular
disclosed embodiments described above, but should be determined
only by a fair reading of the claims that follow.
* * * * *