Workstring Disconnect Tool and Method of Use

Abstract

A tool for economically, efficiently, and reliably separating a workstring in a wellbore is disclosed.

Description

FIELD OF THE INVENTION

The invention pertains to tools for allowing rapid and economical disconnection of a workstring in a wellbore.

BACKGROUND OF THE INVENTION

Drilling technology has evolved allowing wells to be drilled directionally so that larger portions of the wellbore can reside within the hydrocarbon bearing deposit, thus increasing productivity. Wells are increasingly being directionally drilled. Directional drilling introduces new challenges, including sticking of the workstring.

When the workstring lies on the low side of a directional well bore and the well is in an overbalanced pressure state, the workstring often becomes differentially stuck. The method for fishing a stuck workstring requires releasing of the workstring above the point of sticking and running back in with a fishing tool assembly in order to jar the stuck workstring free.

Conventional methods of releasing from and reconnecting the workstring are time consuming and costly. It is desirable to provide an efficient and cost-effective device and method for releasing a workstring “above” (that is, nearer to the surface) a stuck portion of a workstring, returning to efficiently re-couple to the stuck workstring portion with a fishing tool, for example, ajar, and proceeding with drilling operations once the stuck portion of the workstring has been freed.

SUMMARY OF THE INVENTION

The invention is a disconnect tool for separating portions of a workstring in a wellbore. If a workstring becomes stuck, it is necessary to “unlink” the portion of the workstring above the stuck section, so it can be removed from the wellbore and a fishing tool, such as a jar, can be run downhole to attempt to free the stuck section of workstring. (Those of skill in the art will recognize that terms such as “above” and “up” are understood to mean “closer to the surface,” and that “below” and “down” mean “further from the surface.” These conventions are necessary because, with the use of directional drilling techniques, the affected portion of the workstring may be horizontal, or nearly so.)

The tool comprises an upper body, a lower body, and a ball seat sub that can be shifted from a first (initial) position to a second position. In the first position, the ball seat sub maintains a mechanical linkage (such as, for example, by the use of intermeshed splines) with the upper body and with the lower body, so that the upper body, ball seat sub, and lower body are rotationally locked together. Thus, with the ball seat sub in the first position, the disconnect tool acts simply as another link in the workstring.

Should the portion of the workstring below the disconnect tool become stuck, the disconnect tool can be utilized to separate the upper body and the portion of the workstring above the disconnect tool from the lower body and the stuck portion of the workstring. This action is accomplished by dropping or pumping a shifting ball down the workstring to seat on the ball seat of the ball seat sub. Hydraulic pressure is then used to release a retaining device, such as by shearing shear screws or pins, and allowing the ball seat sub to shift down relative to the upper body, releasing the mechanical linkage between the upper body and the ball seat sub.

With the ball seat sub in this second position, the upper body and the ball seat sub (and, thus, the lower body) are no longer rotationally locked. In a preferred embodiment of the invention, the linkage between the upper body and the lower body is a left-handed threaded connection, so that continued normal (clockwise) rotation of the workstring will separate the upper body from the lower body. Once separated, the upper body and the portion of the workstring above it can be withdrawn from the wellbore.

Additionally, in a preferred embodiment of the invention, the lower body is provided with a right-handed thread external retrieval thread, so that an appropriate retrieval tool may be run downhole and threaded onto the lower body to begin retrieval operations. The retrieval tool may be integrated with, or merely attached to, a fishing tool, such as a jar or other device. Upon completion of fishing operations, the intact workstring may be removed from the wellbore or used to continue downhole operations.

Those of skill in the art will recognize that multiple workstring disconnect tools of the present invention can be spaced at various locations in the workstring, and may, for example, be provided with variously sized ball seats. In this way, the operator may have a choice of which of the tools to use to separate the workstring, thus allowing a choice of where along the workstring the separation will occur.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross sectional view of a workstring disconnect tool of the present invention configured to run in to a wellbore.

FIG. 2 is a partial cross sectional view of a retrieving sub for use with the present invention.

FIG. 3 is a partial cross sectional view of a workstring disconnect tool of FIG. 1, with a shifting ball in its initial position.

FIG. 4 is a partial cross sectional view of a workstring disconnect tool of FIG. 1 in the releasing position.

FIG. 5 is a partial cross sectional view of a workstring disconnect tool of FIG. 1 after completion of the releasing operation.

FIG. 6 is a partial cross sectional view of the lower body of a workstring disconnect tool of FIG. 1 with a retrieving sub (FIG. 2) ready to be engaged.

FIG. 7 is a partial cross sectional view of the lower body of a workstring disconnect tool of FIG. 1 in sealing engagement and mechanical linkage with a retrieving sub (FIG. 2).

FIG. 8 is a partial cross sectional view of the upper body of a workstring disconnect tool of FIG. 1.

FIG. 9 is a side view of a ball seat sub of the present invention.

DETAILED DESCRIPTION

Referring to FIG. 1, a workstring disconnect tool 10 of the present invention is shown in its run-in configuration. Workstring disconnect tool 10 comprises workstring coupler 14, upper body 12, ball seat sub 70, and lower body 42. Upper body 12 and lower body 42 are connected by the intermeshing of upper body internal thread 22 and lower body external thread 46. This threaded relationship is preferably left handed, so that when the internal interlock of the workstring disconnect tool 10 is disengaged as described below, continued normal rotation of the workstring will separate upper body 12 and lower body 42.

Referring also to FIG. 9, sealing between the upper body 12 and the ball seat sub 70 is provided by upper ball seat seal 30, which is positioned in upper seal groove 72, and lower ball seat seal 32, positioned in lower seal groove 76. Shearable device 40 (such as shear screws or pins) holds ball seat sub 70 in its first position relative to upper body 12, by engagement with shearing spotface 74. Sealing between upper body 12 and lower body 42 is provided by the engagement of upper body sealing surface 20 with connector seal 34.

In the run-in position, upper body internal keyway 18 (see, also, FIG. 8), comprising, for example, splines, intermeshes with ball seat sub external keyway 80 to rotationally lock ball seat sub 70 to upper body 12, and thus (via workstring coupler 14) to the portion of the workstring above the workstring disconnect tool 10. S Similarly, ball seat sub external keyway 80 simultaneously intermeshes with lower body internal keyway 48, rotationally locking ball seat sub 70 to lower body 42.

Referring now to FIGS. 1, 3-5, should the workstring become stuck below workstring disconnect tool 10, the tool can be utilized by the following process. Shifting ball 90 is dropped or pumped downhole through the workstring (not shown) to seat on ball seat 86. Once shifting ball 90 is in sealing engagement with ball seat 86, hydraulic pressure is increased, shearing shearable device 40, such as shear screws or pins. (Those of skill in the art will recognize that a plurality of shear screws or shear pins spaced around the circumference of the ball seat sub will be desirable.) The hydraulic pressure then shifts ball seat sub 70, placing ball seat sub 70 in its second position. In this position, upper body internal keyway 18 (see, also, FIG. 8) is separated from ball seat sub external keyway 80, so that ball seat sub 70 is no longer rotationally locked to upper body 12.

In this configuration, continued normal (clockwise) rotation of the workstring, will disengage the left-handed threaded relationship between upper body internal thread 22 and lower body external thread 46, separating upper body 12 from lower body 42. The workstring may now be withdrawn from the wellbore, pulling with it upper body 12, ball seat sub 70, and shifting ball 90. Lower body 42 and the continuation of the workstring (not shown) connected to lower body 42 at lower workstring connection 56 remain in the wellbore, awaiting rescue. As the workstring is withdrawn, drain holes 16 allow the outflow of well fluid from the interior of the workstring.

Referring now to FIGS. 6 and 7, the connection of a retrieval tool 60 to lower body 42 is shown. Retrieval tool 60 comprises an internal retrieval thread 66 for engagement with external retrieval thread 52 on lower body 42. Retrieval tool 60 may be any type of, or (as is more likely the case) may be coupled to (via retrieval tool coupler 62), any type of tool, such as, for example, a jar, designed to recover a stuck toolstring.

As retrieval tool 60 is positioned relative to lower body 42, lower end guide 68 assists in correct alignment. As internal retrieval thread 66 engages external retrieval thread 52 on lower body 42, the normal (clockwise) rotation of the workstring will tighten the threads together, until torque shoulder 64 engages lower body upper end 44, and retrieval tool seal 36 is in sealing engagement with lower body sealing surface 54.

Those of skill in the art will understand that the descriptions above are by way of example only, and that variations on the above can be made without departing from the spirit of the invention.

Claims

1. A disconnect tool for separating a workstring in a well bore, comprising

an upper body,

a lower body, selectively connectable to said upper body, and

a ball seat sub, selectively movable from a first position to a second position, wherein in said first position, said ball seat sub is rotationally locked to both said upper body and said lower body, and in said second position said ball seat sub is not rotationally locked to said upper body.

2. The disconnect tool of claim 1, wherein the selective connection between said upper body and said lower body is a left-handed threaded connection.

3. The disconnect tool of claim 1, wherein said ball seat sub is selectively movable by use of hydraulic pressure.

4. The disconnect tool of claim 1, wherein said lower body additionally comprises a retrieval connection.

5. The disconnect tool of claim 4, wherein said retrieval connection is a sealable connection.

6. The disconnect tool of claim 4, wherein said lower body said retrieval connection is an exterior, right-handed threaded connection on said lower body.

7. The disconnect tool of claim 1, wherein said ball seat sub is retained in said first position by a plurality of shearable devices.

8. The disconnect tool of claim 7, wherein said shearable devices are shear screws.

9. The disconnect tool of claim 7, wherein said shearable devices are shear pins.

10. A method of disconnecting portions of a workstring in a wellbore, comprising

providing as part of the workstring a disconnect tool comprising an upper body, a lower body, and a ball seat sub, wherein said ball seat sub maintains a rotational lock to said upper body and said lower body, and wherein said upper body and said lower body are selectively connected, shifting said ball seat sub so that it is not rotationally locked to said upper body, and

disconnecting said upper body from said lower body.

11. The method of claim 10, additionally comprising the step of providing a left-handed threaded connection as the selective connection between said upper body and said lower body.

12. The method of claim 10, additionally comprising the step of providing said lower body with a selective connection for a retrieval tool.

13. The method of claim 10, wherein the step of providing said lower body with a selective connection for a retrieval tool additionally comprises the step of providing a right handed threaded connection on said lower body.

14. The method of claim 10, additionally comprising the step of providing a sealable connection for a retrieval tool on said lower body.

15. The method of claim 12, additionally comprising the step of providing a sealable connection for a retrieval tool on said lower body.

16. The method of claim 14, additionally comprising the step of continuing well operations without removing the workstring from the wellbore.

17. The method of claim 15, additionally comprising the step of continuing well operations without removing the workstring from the wellbore.