BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of one embodiment of tool for movement within a passage having a fluid conduit sheath;
FIG. 2 is a schematic diagram of a longitudinal cross section of the tool of FIG. 1;
FIG. 3 is a cross sectional view of the tool of FIG. 1 taken along line 3-3;
FIG. 4 is a cross-sectional view of the tool of FIG. 1 taken along line 4-4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Patent Application
20080047715
