This invention pertains to downhole equipment for oil and gas wells. More particularly, it pertains to a downhole separation apparatus for use on a wellbore pipe string such as a coiled tubing string and., more particularly, this invention relates to an apparatus for separating the upper portion of a pipe string from the lower portion of the pipe string and bottom hole assembly or BHA.
During the drilling, work over, or plug and abandonment of oil and gas producing wellbores, a variety of downhole tools may be attached to the lower portion or bottom hole assembly of a pipe or coiled tubing string. The attached tools are utilized to perform various functions within the wellbore and the bottom hole assembly may be provided with a variety of stabilizers, reamers, hole deviation devices, drill collars, and the like that enhance the wellbore characteristics such as its shape, geometry and direction.
It is often desirable to release the lower portion or bottom-bole of a pipe or coiled tubing pipe string from the upper portion when the lower portion is still in the wellbore. This occurs when a tool is inserted in the wellbore on the pipe string and released in order to provide some function after the pipe or coiled tubing string is removed. It also occurs when a tool or the BHA becomes stuck in the wellbore and the pipe or coiled tubing string must be removed from the wellbore, independent of the tool or BHA so that a fishing tool string may be placed in the wellbore in order to try to retrieve the stuck tool or BHA, The upper and lower portions of a pipe or coded tubing pipe string are typically released from each other by an intervening tool separation device that has detachable upper and lower sections or subs.
Some tool separation devices have mechanical separation mechanisms that employ shear pins or shear screws as a principal component of the release mechanism. Such separation devices have a number of shortcomings. The shear pins of these devices may prematurely separate when the pipe of coiled tubing string is in the wellbore causing the unintended release of the attached tool or BHA. A separated portion of a shear pin may also jam the release mechanism impeding or preventing, the release of the attached tool. There is also the risk that a shear pin or a separated portion of a shear pin will stray into and remain in a lower or bottom sub portion of the separation device after separation from the pipe or coiled tubing string. A separated shear pin in the bottom sub of a separation device may prevent or impede reengagement of the upper portion of the tool separation device with the bottom sub portion at a later time.
The majority of tool separation devices have hydraulic separation mechanisms which also have shortcomings. The hydraulic separation mechanisms of many of these tool separation devices often utilize a collet mechanism that is released by a piston or ball. The piston or ball of these mechanisms is often left in the lower or bottom sub portion of the separation device when the upper portion is released. A ball left in the bottom sub portion may prevent an operator from subsequently circulating fluid through the bottom sub. The hydraulic separation mechanisms of other such devices suffer from unreliable tool release mechanisms or require high pressures to release a tool from the pipe or coiled tubing string.
Consequently, there is a need for a new tool separation apparatus having improved piston and collet configurations that will reliably release a tool or BHA from a pipe or coiled tubing suing without the aforementioned negative attributes.
The present invention provides a tool separation apparatus that satisfies the aforementioned needs. The separation apparatus is comprised of a collet body, a bottom sub, and a piston collet positioned within the collet body. Collet fingers on the upper end of the piston collet are releaseably retained on an internal abutment surface at the upper end of the collet body. The collet body has a plurality of collet fingers at its lower end that are threadedly engaged with the internal profile of the upper end of the bottom sub. The upper end of the collet body is attached to a pipe string the lower end of the collet body and the lower end of the bottom sub is attached to a tool or a bottom hole assembly.
The piston collet contains an internal profile such that a circulation bail of a given size will seat and substantially block the circulation of fluid through the separation apparatus and fluid pressure in the pipe strata, and piston collet above the circulation bail. When the increased fluid pressure in the piston collet exceeds the gripping, force exerted by the collet fingers of the piston collet on the abutment surface of the collet body the piston collet will shift downward. When the piston collet moves downward position, the collet fingers of collet body collapse so that splined features on the collet fingers of the collet body align and collapse into slots on the piston collet to release the collet body from the bottom sub and thus the bottom hole assembly from the pipe string.
The collet body (15) and bottom sub (10) have central bores, (135) and (140) respectively, in communication with the central bore of the pipe string. The collet body (15) and bottom sub (10) are threadably connected to each other by means of box connection (40) of bottom sub (10) and pin connection (35) of collet body (15). Collet body (15) also has a plurality of collect fingers (105) with internal splined features (95). Seal (75) prevents fluid from entering or exiting through abutting faces of collet body (15) and bottom sub (10).
Positioned within the collet body (15) and bottom sub (10) is a tubular piston collet (20). Piston collet (20) has an upper radially outwardly extending latching shoulder (50) comprised to a plurality collet fingers (60), radial slots (90), and external splined groove features (100). Piston collet (20) is axially aligned with collet body (15) and bottom sub (10) with the latching shoulder (50) in contact with the internal radial abutment surface (55) of collet body (15). The annulus between piston collet (20) and the internal surface of collet body (15) is sealed by seal (70). The splined groove features (100) of piston collet (20) interlock with spline features (95) of the collet body (15) to prevent rotational movement of piston collet (20) within collet body (15) and the slots (90) are configured to receive the spline features (95) of the collet body (15) when piston collet is shifted along the collet body.
The engagement of collet fingers (60) of shoulder (50) of piston collet (20) with abutment surface (55) of collet body (15) will retain the piston collet (20) in place without relying on shear screws which are used with many current downhole separation devices. Retaining the piston collet (20) in place by engagement of shoulder (50) and surface (55) allows the downhole separation apparatus (5) and the pipe string to be jarred during operations while reducing the likelihood of premature separation of the BHA from the pipe string. Often such premature separation of a tool separation device is due to connection failure caused when a shear pin (or screw) is sheared as the pipe string is jarred.
In another embodiment, a plurality of shear screws (45a) shown in
The latching shoulder (50) of piston collet (20) holds against abutment shoulder (55) of collet body (15) until a circulation ball is pumped through the pipe string or coiled tubing string and lands on seat (65) inside the piston collet (20) to create a fluid pressure on the piston collet that collapses the collet fingers (60) to disengage the piston collet from the abutment shoulder (55). The amount of force required to downwardly shift the collet piston (20) while collapsing the collet fingers (60) inward from abutment surface (55) of the collet body (15) can be varied by altering the number and or length of slits (150), the thickness of each of the fingers of the collet (20), and the angle of latching shoulder (50) with a corresponding angle on shoulder (55) in collet body (15)). This force can be adjusted to suit the particular application.
The abutment shoulder (115) of the piston collet (20) limits axial travel of the piston collet (20) upon separation but allows the piston collet (20) sufficient downward axial travel to place the smaller diameter (85) of piston collet (20) below the lower end of collet body (15) so that the collet fingers (105) can collapse, as seen in
Use of the piston collet (20) gives the downhole separation apparatus (5) the ability to withstand repeated jarring impacts as is well known in the art) while substantially reducing the potential for premature separation of the BHA from the pipe string and without the use of shear screws that are typically employed to retain a piston assembly in place in other downhole separation devices.
Another advantage of the piston collet (20) of separation apparatus (5) is that piston collet (20) does not have to be collapsed for assembly or disassembly of the apparatus (5). This eliminates the need for special tooling to collapse the fingers (60) of the collet (20).
For assembly of the downhole separation apparatus (5), the piston collet (20) is inserted into the collet body (15) until shoulder (50) of piston collet (20) contacts shoulder (55) of bottom collet body (15). Splined features (95) of collet body (15) are aligned with groove features (100) of piston collet (20) while piston collet (20) is inserted into collet body (15). Collet body (15) is then inserted into bottom sub (10) and threadably attached via threads (35) and (40) of the collet body (15) and bottom sub (10). The shear screws (45a) can then be inserted if being utilized. The downhole separation apparatus (5) is now complete.
As shown in
When a tensile load is applied to the pipe string, by pulling the pipe string from the surface or otherwise, the collet body (15) of the downhole separation apparatus (5) is separated from the bottom sub (10) as shown in
It is thought that the downhole separation apparatus (5) presented herein as well as its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the parts thereof without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form described herein being merely art example embodiment of the invention.
This application claims priority to U.S. provisional application Ser. No. 61/937,222 filed Feb. 7, 2014 entitled “Downhole Separation Apparatus and Method”, the entire content of which is hereby incorporated by reference.
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