A lockable swivel (4) for use in drilling applications which allows the operator to selectively engage and disengage the swivel (4). The lockable swivel (4) is comprised of a locking mandrel (7) carried in a body (3) which engages, upon actuation, splined surfaces (20, 21) within the swivel mandrel (5) thereby locking the two together. Various methods for the use of the lockable swivel (4) in wireline and other drilling operations are demonstrated.
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0. 54. A drill string for use with a top drive unit and a rotary table comprising:
an assembly joint located between the top drive unit and a wireline access sub;
a lubricator joint located between the wireline access sub and a lockable swivel; and
a pipe string below the lockable swivel passing through the rotary table.
0. 46. A method to perform drilling services using a top drive assembly, the method comprising:
connecting a lockable swivel to a drill string above a rotary table and below an access sub;
unlocking the lockable swivel;
deploying a tool through the access sub, the lockable swivel, and the drill string;
rotating the drill string below the lockable swivel with the rotary table; and
holding the access sub stationary with the top drive assembly.
0. 34. A lockable swivel comprising:
a lower body having a first connection to a drill string, a first spline, and a bore;
a swivel mandrel to be received into said bore, said swivel mandrel including a second connection to the drill string and a second spline;
a retainer configured to retain said swivel mandrel within said lower body; and
said second spline configured to engage said first spline in a locked configuration and disengage in a swivel configuration.
0. 22. A lockable swivel, the swivel comprising:
a body having a first spline, a first connection to a drill string at a first end, and a bore to receive a swivel mandrel at a second end;
a retainer to retain said swivel mandrel within said body;
said swivel mandrel having a second spline configured to cooperate with said first spline and to actuate from an unlocked position to a locked position; and
said swivel mandrel having a second connection to the drill string.
1. A lockable swivel comprising
a retainer sub,
a lower body providing a cooperating surface for engagement with to engage a locking mandrel, said lower body connected to the retainer sub and enclosing the locking mandrel,
a the locking mandrel providing cooperating surfaces for engagement with the lower body,
a swivel mandrel,
a retainer nut connected to the lower body and enclosing the swivel mandrel,
means for engaging the cooperating surface means between engaging the locking mandrel and the swivel mandrel to permit relative rotational movement.
0. 57. A method of using a swivel in a drill string to perform wireline services, wherein the drill string includes a wireline access device, the method comprising:
connecting the swivel in the drill string above a rotary table and below the wireline access device; and
unlocking the swivel such that the portion of the drill string above the swivel is prevented from rotation while the portion of the drill string below the swivel can rotate freely and thus the drill string below the swivel can be rotated by the rotary table without having to remove the wireline access device.
11. A method of using a swivel in a drill string to perform wireline services, wherein the drill string includes a wireline access device, the method comprising the steps of:
connecting the swivel in the drill string above a rotary table and below the wireline access device; and
unlocking the swivel such that the portion of the drill string above the swivel is prevented from rotation while the portion of the drill string below the swivel can rotate freely and thus the drill string below the swivel can be rotated by the rotary table without having to remove the wireline access device.
4. An in-line swivel apparatus for use in wireline operations on a drilling operation comprising:
a tubular retainer sub providing a threaded connections for connecting the tubular body to the connection to a drill string,
a first tubular lower body providing spline surfaces for engaging to engage a locking mandrel,
a second tubular body top sub providing cooperating spline surfaces for engaging the to engage surfaces of the locking mandrel and to retain a swivel mandrel,
a bearing means connected to the tubular body top sub to permit rotation of the swivel mandrel,
a the locking mandrel providing first cooperating surfaces for engaging to engage the spline surfaces of the first tubular lower body, and second cooperating surfaces for engaging to engage the swivel mandrel.
0. 55. A method of using a lockable in-line swivel to recover a pipe string of a drill string, the method comprising:
connecting the swivel in the drill string, wherein the swivel is located between a top drive unit and a rotary table,
locking the swivel,
holding torque on the drill string with the top drive unit,
reciprocating the drill string longitudinally to work torque down the pipe string, and
thereafter affixing the pipe string to the rotary table to continue holding the torque on the pipe string while unlocking the swivel to thereby permit rotation of the drill string below the swivel without disengagement of wireline entry devices when present in the drill string above the swivel.
6. A method of using a lockable in-line swivel for the purpose of recovering a pipe string of a drill string, the method comprising the steps of:
connecting the swivel in a drill string, wherein the swivel is located between a top drive unit and a rotary table,
locking the swivel,
holding torque on the drill string with the top drive unit,
reciprocating the drill string longitudinally to work torque down the pipe string, and
thereafter affixing the pipe string to the rotary table to continue holding the torque on the pipe string while unlocking the swivel to thereby permit rotation of the drill string below the swivel without disengagement of wireline entry devices when present in the drill string above the swivel.
15. A method of using a swivel in a drill string to perform wireline services, wherein the drill string has a wireline access device, the method comprising the steps of:
connecting the swivel in the drill string above a rotary table and below the wireline access device such that the swivel can alternate from a locked position, in which the portion of the drill string below the swivel does not rotate independently of the portion of the drill string above the swivel, to an unlocked position in which the swivel allows the portion of the drill string below the swivel to rotate independently of the portion of the drill string above the swivel; and
selectively alternating the swivel between its locked position and its unlocked position.
0. 56. A method of using a lockable in-line swivel to recover a pipe string of a drill string, the drill string having a wireline entry device, the method comprising:
connecting the in-line swivel in the drill string above a rotary table and below the wireline entry device and a top drive unit,
engaging the drill string below the swivel on the pipe string with the rotary table,
applying torque to the pipe string with the rotary table,
holding the torque on the pipe string with the rotary table,
locking the in-line swivel,
releasing the torque held by the rotary table such that the torque on the pipe string is transferred to the locked in-line swivel and top drive unit,
reciprocating the drill string longitudinally to distribute the torque evenly over the entire length of the drill string, and
thereafter affixing the pipe string to the rotary table to continue holding the torque on the pipe string while unlocking the swivel to thereby permit rotation of the drill string below the swivel without disengagement of the wireline entry device.
8. A method of using a lockable in-line swivel for the purpose of recovering a pipe string of a drill string, the drill string having a wireline entry device, the method comprising the steps of:
connecting the in-line swivel in the drill string above a rotary table and below the wireline entry device and a top drive unit,
engaging the drill string below the swivel on the pipe string with the rotary table,
applying torque to the pipe string with the rotary table,
holding the torque on the pipe string with the rotary table, locking the in-line swivel,
releasing the torque held be the rotary table such that the torque on the pipe string is transferred to the locked in-line swivel and the top drive unit,
reciprocating the drill string longitudinally to distribute the torque evenly over the entire length of the drill string, and
thereafter affixing the pipe string to the rotary table to continue holding the torque on the pipe string while unlocking the swivel to thereby permit rotation of the drill string below the swivel without disengagement of the wireline entry device.
2. The lockable swivel of
5. The in-line swivel of
7. The method of
18. The method of
19. A drill string for use with a top drive unit and a rotary table comprising:
an assembly joint;
a wireline access sub;
a lubricator joint;
a lockable swivel according to
a pipe string,
wherein when the drill string is in use
the assembly joint is located between the top drive unit and the wireline access sub,
the lubricator joint is located between the wireline access sub and the lockable swivel,
the lockable swivel is located between the top drive unit and the rotary table, and
the pipe string is located below the lockable swivel.
0. 23. The lockable swivel of
0. 24. The lockable swivel of
0. 25. The lockable swivel of
0. 26. The lockable swivel of
0. 27. The lockable swivel of
0. 28. The lockable swivel of
0. 29. The lockable swivel of
0. 30. The lockable swivel of
0. 31. The lockable swivel of
0. 32. The lockable swivel of
0. 33. The lockable swivel of
0. 35. The lockable swivel of
0. 36. The lockable swivel of
0. 37. The lockable swivel of
0. 38. The lockable swivel of
0. 39. The lockable swivel of
0. 40. The lockable swivel of
0. 41. The lockable swivel of
0. 42. The lockable swivel of
0. 43. The lockable swivel of
0. 44. The lockable swivel of
0. 45. The lockable swivel of
0. 47. The method of
0. 48. The method of
0. 49. The method of
0. 50. The method of
0. 51. The method of
0. 52. The method of
0. 53. The method of
0. 58. The method of
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This application claims the benefit of International Application No. PCT/US97/24043, filed Dec. 27, 1997, which claims the benefit of U.S. Provisional Application No. 60/034,799, filed Dec. 31, 1996.
1. Technical Field
The present invention relates generally to a drill string apparatus for use in drilling operations, and more particularly to an apparatus and method for selectively locking an inline swivel to permit rotational movement of the drill string.
2. Background Art
In wireline operations, it is often desirable to selectively allow the drill string to rotate freely while the wireline operator manipulates the wireline.
Previously, if the operator desired to rotate the drill string during wireline operations, the wireline was pulled from the well bore and the entry devices were disengaged from the drill string. The removal of the wireline could be avoided if an inline swivel was placed in the drill string between the wireline device and the rotary table. This arrangement would permit rotation to be accomplished with a wireline in place, but effectively disengaged the top-drive unit from its preferred role of providing both lifting power and rotation to the drill string.
The invention disclosed herein provides an apparatus which would allow the connection of various wireline devices 106 to be placed in the drill string 100 between the top drive unit 102 and the rotary table 114 of a conventional drilling rig throughout wireline operations. Such devices 106 as the Boyd Borehole Drill Pipe Continuous Side Entry Or Exit Apparatus (such as described in U.S. Reissue Pat. No. 33,150) or applicant's Top Entry Sub Arrangement (as described in U.S. Pat. No. 5,284,210) may both be utilized for various wireline operations.
Referring to
Accordingly, it is the primary purpose of the invention disclosed herein to provide an apparatus and method which permits the wireline entry devices 106 described above to be left in the drill string 100 during all operations involving the wireline operation. This avoids the time consuming makeup and disengagement of the entry tools 106 required to safely permit entry of the wireline into the well bore. If rotation and longitudinal movement is desired with the invention disclosed herein, the wireline alone is removed from the wellbore, but the entry tool 106 remains in place and the swivel 110 is locked to provide transmission of all rotation through the swivel 110 into the pipe string 112.
At other times, the operator using a top-drive unit 102 may desire to pick up the drill string 100 and yet maintain torque which has been put into the pipe string 112 in pipe recovery operations. This is best done by engaging the swivel 110 in locked position and picking up with the top drive unit 102. As the torque is worked through the drill string 100, additional wireline operations may be desired. In this eventuality, the operator would set the drill string 100 down, disengage the swivel 110, continue to rotate with the rotary table 114 and continue the wireline operations.
Using prior conventional technology, the drill pipe was separated and raised high above the rig floor on each run in order to change out tools. Although the pipe can be rotated, the operator could not circulate or reciprocate the pipe during these periods. Circulation was achieved by adding a pump-in sub and another T.I.W. safety valve immediately above the existing T.I.W. valve; which, however, put the disconnect or break point between the upper T.I.W. valve and the swivel several feet above the rig floor creating a safety hazard while operating the rig tongs.
Further, since the tool strings must be stripped in and out beneath the upper assembly, a lubricator or tool protection device could not be used and all tools and explosives were brought onto the rig floor unshielded and unconfined. In the event of an inadvertent detonation of the explosive string shot or perforators, all personnel on the rig floor were totally exposed to this unnecessary life-threatening hazard.
Once rigged-up and going in the hole using conventional technology such as the Boyd side-entry sub, the wireline passed through the acute angle in the side entry sub. This caused excessive wearing of the wireline and creates sever grooving in the sub. The single rubber pack-off, which is commonly used with this system, is very susceptible to leaking and/or line gripping and stoppage during pump-down operations. The system cannot be used when working under surface pressure and with the need to utilize a grease injector and wireline blow out preventers (BOPs).
During pipe recovery operations, both right and left-hand torque must be worked down-hole using the rig tongs. This is a procedure has long been recognized to be one of the greatest safety hazards to be encountered during pipe recovery operations. When using this prior technology, pipe tongs were attached to the drill string and secured to the rig to hold torque that had been put into the drill string from the rotary table or top drive unit. With the present invention, this torque can be maintained while continuing circulation and wireline operation.
These and other objects, features, and advantages of the present invention will become apparent from the drawing and the descriptions given herein.
In
The retainer sub 1, locking mandrel 2, and lower body 3 of the lockable swivel apparatus 110 engage the top sub 4 of an inline swivel. Brass packing rings 27 and washpipe packing 26 seal swivel mandrel 5 permitting fluid communication through the annulus of the inline swivel apparatus without leakage. Swivel mandrel 5 is secured to the circumferentially spaced brass wear ring 31, bearing 29, packing 28 and 30 by a bearing retainer nut 6, which is threadably engaged on the top sub 4 by threads 33 and 33′. As shown in
Hydraulic fitting ports 40 and 41 provided in the lower body 3 are disposed on either side of a dynamic seal means 17 in a chamber formed between exterior of the locking mandrel 2 and the interior wall 43 of the lower body 3 to move the locking mandrel 2 either up or down and thereby into or out of engagement with the splines 21 on the swivel mandrel 5 and the splines 20 in the lower body 3. The locking mandrel 2 moves up or down as provided and is stopped by shoulder 15 from moving into retainer sub 1.
Washpipe packer or seal means 45 and 46 are provided to make a hydraulic seal in chamber 43′ to enable an operator on the rig floor 116 to selectively move the locking mandrel 2 into and out of engagement with the swivel mandrel and to thereby control undesired rotation of the pipe string 112 by actuating a hydraulic pump.
In the preferred embodiment, standard hydraulic lines are attached to hydraulic fitting ports 40 and 41 and connected by hydraulic lines to a pump controlled by the operator in a manner well known to those in the industry. The operator switches the flow of hydraulic fluid to port 40 if locking of the swivel is desired, and to port 41 if unlocking of the swivel is desired.
When used in conjunction with wireline services on directional drilling operations, the magnetic or gyro-type tools have direct entry into the pipe string 112 through the top entry sub (a wireline access sub 106). Once the tools have been landed in the down-hole-guide sub, or in the wet-connect sub, the pipe string 112 can then be oriented using the rotary table 114, while maintaining the swivel 110 in the unlocked position. Once the desired orientation has been attained, the pipe can then be held in position by locking the swivel and engaging the back-brake on the top drive unit 102.
Should minor adjustments in the orientation be required, this can be easily accomplished since the locking mechanism in the swivel 110 incorporates a splined shaft which provides eighty three separate orientations per revolution. Utilization of this package enables drilling two or three joint per connection, depending on rig height, and eliminates holding the back-torque with the rig tongs.
In pipe recovery operations, once the downhole package has been assembled, the wireline tools always have direct entry into the pipe string 112 which eliminates having to separate and re-connect the pipe string 112 each run. Also, the tools can be fully lubricated which minimizes any bending, flexing or jarring of sensitive instrumentation. All explosive devices, such as string shots, cutters, severing tools and perforating guns are contained within the lubricator while in close proximity of the rig floor 116. This minimizes exposure to potential injury in the event of an inadvertent detonation. The assembly enables operation under surface pressure, while performing pump-down operations, and while employing a grease injector system. Between wireline runs, the operator retains the ability to continue circulation and reciprocation of the pipe string 112, thus preventing additional subsidence and sticking. During actual operations both make-up and reverse torque can be applied to the pipe string 112 and worked-down without utilizing the rig tongs. Prior to the ability to maintain the torque by setting the swivel 110 in the locked position, torque was maintained on the drill string by attaching pipe tongs to the string and cabling the end of the tong to the drilling structure while the operator reciprocates and manipulates the string. The disengagement of the pipe tong cabling while torque was being applied caused the tongs and cabling to dangerously rotate rapidly around the rig floor.
During pipe recovery operations, the wireline engineer must apply right hand, “make-up,” torque to the pipe string 112 and work it down in order to assure that the entire string is sufficiently tight before applying the left hand, “back off,” torque. With the pipe string 112 setting on the slips in the rotary table 114, usually at neutral weight, the right hand torque is applied to the pipe string 112 in an amount less than the full make-up torque of the string and then releasing or relaxing the brake on the pipe string 112. Non-absorbed torque will “come back.” This process is then repeated three to four times, with each iteration providing greater amounts of torque, until a predetermined amount based upon the recommended maximum torque load for the type of pipe and connections has been reached. The drilling engineer also uses the behavior of the pipe string 112 during this process to determine the amount of torque the hole is “trapping” or whether the torque is being distributed evenly through-out the pipe string 112 or encountering premature build up because of angle changes, dog legs, etc.
With the right hand torque being held securely with the rotary back-brake or the rotary lock, the operator switches the manual control valve on the hydraulic pump from the open/unlocked position to the closed/locked position to begin closing the locking mechanism in the swivel 110. The operator should count the strokes and to observe the sudden pressure increase. If the number of strokes and the pressure change are consistent with the results experienced in the installation phase, the internal lock is completely closed. To assure that the swivel 110 remains in locked position, it is recommended that approximately 500 pounds of back pressure against the lock be maintained.
Referring to
Once satisfied that the pipe string 112 has been sufficiently tightened to the point of accepting left-hand torque without breaking pre-maturely, the pipe string 112 can be placed back on the slips in the rotary table 114. The back-brake or the lock on the rotary table 114 should then be engaged.
With the weight of the pipe string 112 now resting on the rotary table 114, the torque being held with the top drive unit 102 can be slowly transferred to the rotary table 114.
With the torque transferred and the top drive unit 102 disengaged, the operator switches the controls on the hydraulic pump and opens or “unlocks” the swivel 110. As before, the operator should count the strokes and watch the pressure to assure that the swivel 110 is totally open, or “unlocked.” Again, it is recommended that approximately 500 pounds of back pressure be maintained to assure that swivel 110 remains in the open or “unlocked” position. The wireline access sub 106 should then be realigned with the derrick sheave and the top drive unit 102 relocked. The torque can then be released with the rotary table 114. At this point, the engineer may elect to reciprocate the pipe string 112 in order to work out any remaining trapped torque prior to running the free point or other services.
The invention also enables rotating, circulating and reciprocating the pipe while running and pumping-down various wireline tools and performing various services, i.e., end-of-hole gyros, “measure-while-drilling” (M-W-D) retrieval tools, pipe recovery service tools, gamma ray logging devices or total “vertical depth” (T.V.D.) devices and other logging or perforating service tools.
Since the package can be assembled in a variety of configurations, customer preference, operating conditions and job requirements, whether involving directional drilling, pump downs, grease injectors, MWD retrieval, coil tubing or pipe recovery, will strongly influence which configuration is most advantageous for the job to be performed.
Once the chosen packages described above have been installed and tightened, the hydraulic hoses should be attached to the locking swivel 110 and the hand pump. The hoses, the swivel and the hand pump have mated quick-connects which assures that the labeling on the hand pump, closed/locked and open/unlocked corresponds correctly with the direction of movement and position of the internal locking mechanism within the swivel 110.
Lock the rotary table 114, or attach the back-up rig tongs to the joint of pipe in the rotary table 114, and the assembly can be tighten to maximum torque allowed using the top drive unit 102.
Engage the top drive unit 102 and slowly increase the amperage until the maximum foot pounds of torque allowed for the particular drill pipe being used in the upper assembly has been reached. Reduce the amperage to zero and then increase back to maximum allowed amperage at least one or two more times.
Once the assembly has been properly tightened and the top drive amperage reduced to zero, unlock the rotary, or release the back-up tongs, and then open, “unlock”, the swivel.
Use the top drive unit 102 and slowly orient the upper assembly until the wireline access port in the top entry sub (a wireline access sub 106) is in perfect alignment with the wireline sheave in the derrick. The top drive unit 102 should then be locked in this alignment and secured so as to prevent inadvertent unlocking.
Upon making one final check and assuring that the top drive unit 102 is locked in the aligned position and the swivel 110 is in the unlocked position, the assembly will be ready to begin operations.
Patent | Priority | Assignee | Title |
11788379, | Aug 23 2019 | Odessa Separator, Inc. | Gas venting in subterranean wells |
8627890, | Jul 27 2007 | WEATHERFORD TECHNOLOGY HOLDINGS, LLC | Rotating continuous flow sub |
8826992, | Apr 12 2011 | Saudi Arabian Oil Company | Circulation and rotation tool |
9316074, | Nov 27 2012 | Baker Hughes Incorporated | Resettable selective locking device |
9416599, | Jan 06 2010 | WEATHERFORD TECHNOLOGY HOLDINGS, LLC | Rotating continuous flow sub |
9803785, | Aug 04 2010 | Disc brake lock swivel |
Patent | Priority | Assignee | Title |
2100418, | |||
3313345, | |||
3948588, | Aug 29 1973 | REED MINING TOOLS, INC | Swivel for core drilling |
4051456, | Dec 08 1975 | Exxon Production Research Company | Apparatus for establishing and maintaining electric continuity in drill pipe |
4064953, | Jun 22 1976 | Chevron Research Company | Shear sub for drill string |
4074775, | Feb 25 1975 | Fishing Tools, Inc. | Power swivel |
4106575, | Jul 12 1976 | FMC Corporation | Tool string and means for supporting and rotating the same |
4470469, | Apr 01 1980 | SLURRY MINING ENGINEERING INC , WESTFIELD, N J A CORP OF NJ | Swivel head for drilling and mining tool |
4506729, | Feb 22 1983 | Exxon Production Research Co.; Gearhart Industries, Inc. | Drill string sub with self closing cable port valve |
4575359, | May 02 1984 | Bermingham Construction Limited | Rotary drive coupling |
4821814, | Apr 02 1987 | 501 W-N Apache Corporation | Top head drive assembly for earth drilling machine and components thereof |
4981180, | Jul 14 1989 | NATIONAL-OILWELL, L P | Positive lock of a drive assembly |
4992997, | Apr 29 1988 | Atlantic Richfield Company | Stress wave telemetry system for drillstems and tubing strings |
5086844, | Oct 10 1989 | UNION OIL COMPANY OF CALIFORNIA, A CORP OF CA | Hydraulic release oil tool |
5107940, | Dec 14 1990 | Hydratech; HYDRATECHNOLOGY, INC , D B A HYDRATECH, A CORP OF TX | Top drive torque restraint system |
5159226, | Jul 16 1990 | Atlantic Richfield Company | Torsional force transducer and method of operation |
5168943, | Jun 24 1991 | Adjustable bent sub | |
5251709, | Feb 06 1990 | NABORS DRILLING LIMITED | Drilling rig |
5284210, | Feb 04 1993 | OIL STATES ENERGY SERVICES, L L C | Top entry sub arrangement |
5373906, | Mar 08 1993 | TIW Corporation | Orientable guide assembly and method of use |
5388651, | Apr 20 1993 | NATIONAL OILWELL VARCO, L P | Top drive unit torque break-out system |
5396952, | Oct 20 1993 | FORUM US, INC | Drilling rig kelly spinner |
5735351, | Mar 27 1995 | OIL STATES ENERGY SERVICES, L L C | Top entry apparatus and method for a drilling assembly |
5738178, | Nov 17 1995 | Baker Hughes Incorporated | Method and apparatus for navigational drilling with a downhole motor employing independent drill string and bottomhole assembly rotary orientation and rotation |
5996712, | Jan 08 1997 | Smith International, Inc | Mechanical locking swivel apparatus |
GB2307495, | |||
JP5311642, | |||
RE33150, | Jul 17 1989 | Boyd's Bit Service Inc. | Borehole drill pipe continuous side entry or exit apparatus and method |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Sep 01 2002 | SPECIALTY RENTAL TOOLS & SUPPLY, INC | SPECIALTY RENTAL TOOLS & SUPPLY, L P | CONVERSION | 017766 | /0954 | |
Jun 29 2007 | SPECIALTY RENTAL TOOLS & SUPPLY, L P | SPECIALTY RENTAL TOOLS & SUPPLY, L L C | MERGER SEE DOCUMENT FOR DETAILS | 020232 | /0726 | |
Dec 31 2011 | SPECIALTY RENTAL TOOLS & SUPPLY, L L C | OIL STATES ENERGY SERVICES, L L C | MERGER SEE DOCUMENT FOR DETAILS | 029139 | /0610 |
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