Volume compensated shifting tool

[0001] This application claims the benefit of U.S. Provisional Application 60/410,359, filed on Sep. 13, 2002.

[0002] 1. Field of Invention

[0003] The present invention pertains to shifting tools used in subsurface well completions, and particularly to hydraulic shifting tools used in closed hydraulic volumes.

[0004] 2. Related Art

[0005] Shifting tools are commonly used in well completions in which actuation of a tool is brought about by relative movement of a tool element. This can be, for example, opening or closing a valve (e.g., sleeve, ball, or flapper), setting a packer, or initiating an explosive train. The earliest shifting tools were simple mechanical devices that engaged a profile in the tool element to be moved, and the tool element was moved as an operator manipulated the shifting tool.

[0006] More sophisticated shifting tools use hydraulic pressure to apply a force to a moveable element, such as a piston, to induce motion of the element. Existing hydraulic shifting tools generally require a fluid path to the surface or well annulus to permit movement of relatively incompressible well fluids. If such tools are run into a sealed volume, the tool will be stopped from advancing, and the piston will be prevented from moving, unless the fluid within the volume is routed to the surface or well annulus.

[0007] The present invention provides for an apparatus and method of use for a hydraulic shifting tool to be used in a sealed volume in a subsurface well completion to actuate a downhole device, without a fluid return to surface or the well annulus.

[0008] Advantages and other features of the invention will become apparent from the following description, drawings, and claims.

[0013] Referring to FIGS. 1A–1E, a volume compensated shifting tool 10 has, in accordance with an embodiment of the invention, an inner sleeve 12, a compensating piston 14, an actuator piston 16, and a housing 18.

[0014] Inner sleeve 12 is disposed within housing 18 and releasably engages housing 18 with an upper collet 20. Housing 18 carries a locking dog 22, a locator dog 24, an upper spring 26, a lower collet 28, compensating piston 14, and actuator piston 16. Compensating piston 14 and actuator piston 16 are disposed in chambers 30 and 32, respectively, within housing 18. Chamber 32 is in fluid communication with an interior 34 of a tubing (not shown) via a lower port 36, and chamber 30 is in fluid communication with the interior of a tool body 38 (only a representative portion of which is shown) via an upper port 40. Housing 18 also has a balance port 42 on the lower end of housing 18 to allow fluid communication between the interior of tool body 38 and tubing interior 34. Inner sleeve 12 carries a seal 43 on its lower end that seals against the inner wall of housing 18.

[0015] Actuator piston 16 releasably engages housing 18 with lower collet 28. A shifting element 46 is slidably mounted to housing 18 and moves within a slot therein in response to the movement of actuator piston 16. Shifting element 46 engages a moveable assembly 48 that is part of tool body 38. Moveable assembly 48 has a recess 50 terminated on its lower end by a shoulder 52. Shifting element 46 moves within recess 50, causing moveable assembly 48 to move down when shifting element 46 bears on shoulder 52. A lower spring 54 is carried in the lower end of chamber 32 and bears against shifting element 46.

[0016] In operation, shifting tool 10 is initially run in on wireline or other common deployment system. Shifting tool 10 is held in its running-in position by collet 20. Shifting tool 10 is run in until locator dog 24 catches on a matching profile in a nipple or portion of tool body 38 to properly position shifting tool 10.

[0017] With locator dog 24 properly engaged, inner sleeve 12 is displaced downward (FIGS. 2A–2E) relative to housing 18, disengaging upper collet 20. Inner sleeve 12 is displaced, for example by mechanical means, and moved downward until locking dog 22 is locked in place. That secures shifting tool 10 in place. In this position, shifting element 46 is disposed in recess 50. Also, balance port 42 is sealed closed by seal 43 to prevent fluid communication between interior 34 and the interior of tool body 38.

[0018] To move moveable assembly 48 (FIGS. 3A–3E), pressure is applied within interior 34. That pressure is communicated to actuator piston 16 via lower port 36 and displaces actuator piston 16 and shifting element 46 downward. Upon sufficient downward movement, shifting element 46 engages and bears on shoulder 52, causing moveable assembly 48 to move downward.

[0019] The fluid in chamber 32 is generally incompressible, and must therefore be displaced as actuator 16 moves downward. Because the fluid is in communication with the interior of tool body 38, it can be collected in the lower end of chamber 30 via upper port 40. The fluid pressure acts on compensating piston 14, causing it to be displaced upward, pushing against spring 26. The upper end of chamber 30 may be an atmospheric chamber or may hold compressible fluid such as a charge of gas. Thus, energy may be stored in spring 26 and the compressible fluid, if any, in chamber 30. The upper end of chamber 30 is preferably prepressurized with a compressible fluid to compensate for anticipated hydrostatic pressure within tool body 38.

[0020] Compensating piston 14 and the compressible volume in the upper end of chamber 30 allow shifting tool 10 to enter a closed, hydraulically locked volume (i.e., having no hydraulic return path to the surface or into the well annulus). Shifting tool 10 does not merely balance to downhole hydrostatic conditions, but rather carries a displaceable volume into an otherwise hydraulically closed volume. The incompressible fluid in the closed volume must be displaced to allow entry of shifting tool 10 into the closed volume. Shifting tool 10 routes the incompressible fluid into the lower end of chamber 30, as described above. Compensating piston 14 and chamber 30 also allow work to be done by shifting tool 10, such as moving a piston in the closed volume. Thus, only a single fluid path is required to activate shifting tool 10 remotely. Shifting tool 10 can be placed in a system without using a fluid conduit (e.g., by slickline or wireline) and actuated by pressurizing the system, without providing a separate vent or return path for displaced wellbore fluids. Similarly, shifting tool 10 can be used to remove a tool from a hydraulically locked system.

[0021] If an operator wishes to repeat the actuation sequence, perhaps because the operator believes a valve failed to open properly, the operator can pull upward on inner sleeve 12. This pulls actuator piston 16 upwards and allows shifting element 46 to move upward in response to lower spring 54 (FIGS. 4A–4E). Inner sleeve 12 is then lowered to again close port 42. Tubing pressure may then be reapplied to repeat the downward displacement cycle. Alternatively, simply bleeding and reapplying the tubing pressure can also repeat this operation. The charged volume in chamber 30 will work to return the piston substantially to its original position. Similarly, if the operator is ready to retrieve shifting tool 10, the operator pulls upward with sufficient force on inner sleeve 12 to release locking dog 22 and locator dog 24. When shifting tool 10 is pulled out of the hole, balancing port 42 is open to allow flow through shifting tool 10. This allows shifting tool 10 to be removed from a hydraulic lock or reduces the effect of an overbalanced (downward flow) well situation. It also eliminates the requirement of equalizing the well before and after operation to allow installation or removal.

[0022] In the preceding description, directional terms, such as “upper,” “lower,” “vertical,” “horizontal,” etc., may have been used for reasons of convenience to describe the completion valve assembly and its associated components. However, such orientations are not needed to practice the invention, and thus, other orientations are possible in other embodiments of the invention.

[0023] Although only a few example embodiments of the present invention are described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.