Apparatus and method for cementing well liners

Abstract

Apparatus and method for cementing a liner in a well bore in which the apparatus may comprise: a setting tool having a tubular mandrel connected in a pipe string for extension through the liner; a liner wiper releasably disposed within the liner near one end of the mandrel; a plug member for effecting a movable seal behind cement as it is pumped through the pipe string into the liner; a seal assembly sealingly engaging the exterior of the mandrel and the interior of the liner above the liner wiper; and a latch assembly releasably connecting the seal assembly to the liner so as to permit limited axial movement of the mandrel without disturbing the axial position of the seal assembly. In the method of cementing a liner using the apparatus, the force due to pressure applied to the seal assembly, during pumping of cement, is transferred to the liner without transfer to the mandrel.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to apparatus and methods for cementing liners in well bores. More specifically, it pertains to apparatus which permits cementing of liners in well bores without some of the attendant pressure problems of the prior art.

2. Brief Description of the Prior Art

A liner is a section of casing or tubing which is suspended in a well without normally extending to the surface. Cemented liners are utilized for a number of reasons: providing well control, reducing initial cost of casing, more rapid installation than full casing strings, etc. Liners may be installed entirely within outer casing strings or partially in an open hole.

Conventionally, a liner is set and cemented by first lowering the liner and a setting tool, connected to an operating string, into the well bore. The liner is hung, usually on slips, and the setting tool is released from the liner. Then cement is pumped through the operating string, into the liner, and displaced from the liner, usually through a foot valve, into the annular space between the liner and the surrounding casing or well bore.

Usually, at least one plug is introduced into the liner string immediately behind the cement in order to separate the cement from the displacing fluid and to wipe cement from the liner surface as the cement is pushed out of the liner into the surrounding annular space. It is also conventional to utilize at least one additional plug for introduction into the operating string to separate the cement from the displacing fluid and to wipe the cement from the operating string as cement is pumped into the liner. In more recent cementing operations, the plug which is to wipe the operating string is pumped behind the cement until it engages the liner wiper plug and then both plugs are forced downwardly together in the liner string so as to displace cement therefrom and to wipe the liner walls. Such apparatus may be seen in U.S. Pat. No. 3,364,996 -- C. C. Brown and U.S. Pat. No. 3,635,288 -- Lebourg.

In such cementing operations, it is also necessary to provide some sort of seal in the annular space between the setting tool and the surrounding liner since fluid pressure must be maintained in the operating string during the cementing operation. It has been common to provide this seal by attaching a chevron type seal assembly to the setting tool mandrel for sealing engagement with the surrounding liner at some point above the liner wiper plug. However, once the pumpdown plug has engaged the wiper plug and both plugs are forced downwardly through the liner to displace the cement therein, the pressure applied thereto acts against the lower end of the mandrel and the chevron seal assembly applying an upwardly directed force tending to force the operating string out of the well. Therefore, a substantial amount of weight must be maintained on the operating string to prevent this from occurring. In addition, upon removal of the setting tool from the liner, after cementing, a substantial amount of force may be required to overcome the hydraulic head due to fluids surrounding the operating string above the setting tool.

Chevron type seals have sometimes been replaced by inverted swab cups (one-way lip-type seals) to eliminate the problems associated with lifting an operating string against the hydraulic head created by fluids surrounding the operating string. Since the inverted swab cups seal against pressure in one direction only (pressure from below the seals) there is no problem in picking up the operating string and setting tool. However, this does not eliminate the forces acting upwardly on the operating string due to pressures applied to the plug seal and wiper plug as they move downwardly through the liner. Thus, the inverted swab cup still necessitates the maintaining of a substantial amount of weight on the operating string to prevent it from being forced out of the well bore.

In recent years, a seal assembly has been developed which reduces the forces tending to force the operating string out of the well as well as eliminating the problems associated with lifting the operating string against the hydraulic head created by fluids surrounding the operating string. Such assemblies are directly connected in the liner string and provided with a central opening and seal for engagement by a "slick" stinger or mandrel of the setting tool. The forces acting upwardly on the seal assembly are transferred directly to the liner string. However, once cementing is completed, such a seal assembly must be drilled out. This requires additional time and money.

SUMMARY OF THE INVENTION

The cementing apparatus of the present invention includes a setting tool having a tubular mandrel connected in a pipe string for extension through the liner which is to be set. A wiper seal or plug is releasably disposed within the liner near one end of the mandrel and may have a central opening through which cement may be pumped. A pumpdown plug or seal is provided for sliding and sealing engagement with the interior of the pipe string and mandrel, effecting a movable seal behind the cement as it is pumped into the liner. The pumpdown plug is engageable with the wiper plug and movable therewith, upon release of the wiper plug, to effect a movable seal behind the cement as cement is displaced from the liner into the surrounding well bore.

Like in other cementing apparatus, a seal assembly is disposed in the annular space between the mandrel and the liner. However, unlike the prior art, such a seal assembly, which sealingly engages the interior of the liner and the exterior of the mandrel, is releasably connected to the liner by a latch assembly and permits limited axial movement of the mandrel without disturbing the axial position of the seal means.

Since the seal assembly is initially connected to the liner, any pressure acting against the seal, in either direction, is transmitted to the liner and not to the setting tool and operating string as is the case in the prior art. Thus, it is necessary to maintain only enough weight on the operating string to overcome the pressure acting directly on the end of the mandrel. Furthermore, there is no resistance due to hydraulic heads within the space surrounding the operating string when the operating string and setting tool are lifted upwardly relative to the liner.

These are substantial improvements over the prior art. In broad terms, the apparatus of the present invention keeps cement inside and below the setting tool, keeps drilling mud out of the liner while circulating cement through the liner and up the annular space therearound and allows axial movement of the setting tool without disengaging the sealing member. If the mandrel and seal are disengaged from the liner seal bore, it can be reinserted easily. All this is made possible by providing a seal which isolates the interior and exterior of the liner during circulating and sealing operations.

These objects are accomplished by apparatus which is relatively easy to manufacture and operate and is removable without having to drill it out. Many other objects and advantages of the invention will become apparent from a reading of the description which follows in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation view, partially in section, showing a setting tool, liner string and associated apparatus in a well bore in which the liner string is to be cemented;

FIG. 2 is an elevation view, partially in section, showing the apparatus of FIG. 1 after cement has been pumped into the annular space between the liner and the well bore;

FIG. 3 is a longitudinal quarter-sectional view of the setting tool and liner of the present invention, showing the setting tool and associated seal assembly in the initial running in position;

FIG. 4 is a longitudinal quarter-sectional view of the setting tool and liner of FIG. 3, in which the setting tool has been released from the liner and in which cement, followed by a pumpdown plug, has been pumped into the liner;

FIG. 5 is a longitudinal quarter-sectional view similar to FIGS. 3 and 4, in which the pumpdown plug and liner wiper plug have been released and pumped downwardly through the liner displacing cement into the annular space between the liner and well bore;

FIG. 6 is a longitudinal quarter-sectional view similar to FIGS. 3 - 5, showing the setting tool upwardly displaced prior to removal from the well or to indicate that the setting tool has been released from the liner;

FIG. 7 is a longitudinal quarter-sectional view similar to FIGS. 3 - 5, showing the setting tool picked up sufficiently to allow release of the latching mechanism of the associated seal assembly;

FIG. 8, taken along line 8--8 of FIG. 3 is a cross-sectional view illustrating the disposition of the latches of the associated seal assembly in the latched in position; and

FIG. 9 is a cross-sectional view, taken along line 9--9 of FIG. 7, illustrating the disposition of the latches of the seal assembly in the released or unlatched position.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIG. 1 of the drawings, there is shown a liner string 1 disposed near the bottom of a well bore 2. The well bore 2 may or may not be lined by a casing string 3 which may extend to the surface of the well. In any event, there is an annular space 4 between the liner string and the surrounding well bore 2.

The liner string 1 may include a liner hanger 5, liner extension 6, landing area 7 and cementing shoe 8. In addition, a liner packer (not shown) may be attached to the liner string above the liner hanger 5.

Most of the components of the liner string are not materially different from liner components of the prior art. The liner hanger 5 may be provided with slips 9 and a setting cone 10 by which the liner string is supported in the well bore. Such construction is well known in the industry and will not be described in detail herein. The landing area 7 is provided with a seat and latch engaging profile 11 for receiving a liner wiper plug as will be more fully understood hereafter. The cementing shoe 8 is provided with a back pressure or check valve 12 which permits passage of cement from within the liner into the annular area 4 via ports 13.

One material difference in the liner string is the provision of an annular recess 14 by which a liner wiper plug 15 may be initially maintained at a predetermined level within the liner string. In addition, the liner string may be provided with an internal latch profile 16 for engagement by latches of a seal assembly, generally designated by the numeral 17 to be more fully described hereafter.

The liner string 1 is initially attached by rotatably releasable connector means 18 to a setting tool generally indicated by the numeral 19. The setting tool 19 is in turn connected to an operating pipe string 20 which extends to the surface of a well.

Referring also to FIG. 3, the setting tool 19 comprises a tubular mandrel 21, the internal diameter of which may be substantially uniform throughout its length. The external diameter of the mandrel 21 may be reduced at 22 for a purpose to be more fully understood hereafter. Lugs 23 may be attached to the reduced diameter portion 22 of the mandrel to act as a centralizer and as a stop means, as will be seen hereafter. Space is provided between the lugs 23 so that they do not disturb fluid flow in the annular space 24 between the mandrel 21 and the surrounding liner hanger 5.

The upper portion of the setting tool 19 is provided with an annular shoulder 25 and ring 26 forming races for ball bearings 27. This permits the setting tool and operating string 20 to be rotated, without axial displacement, relative to the liner string. The bearing ring 26 is adapted to engage a portion of the liner string to remain stationary during such rotation.

As previously stated, the liner hanger may be provided with an internal latch profile 16 for engagement by the latches of seal assembly 17. Sometimes this latch profile 16 may be located in a setting sleeve 28 which may be attached at the lower end to the liner hanger 5 and at the upper end to a liner packer 29 (only a portion of which is shown).

As previously mentioned, the liner string is initially attached to the setting tool 19 by rotating connector means 18. The rotating connector means 18 may take the form of a lefthand threaded nut 30 which engages coarse lefthand threads 31 on the interior of the hanger setting sleeve 28. The interior of the nut 30 may be provided with longitudinal slots for engagement with corresponding splines 32 on the setting tool 19. Thus rotation of the setting tool 19 in the righthand direction will cause the nut 30 to move upwardly on the splines 32 and to eventually disengage the threads 31 and the setting sleeve 28, effectively releasing the setting tool from the liner string.

As previously mentioned, a liner wiper plug 15 may be releasably disposed within the liner string near one end of the tool mandrel 21. Such a plug may comprise a tubular body 33 having a central opening 34 therethrough. The body 33 may have an upwardly and outwardly flaring portion 35 creating a guide funnel into the central opening 34. A resilient lip-type seal 36 may be attached to the body by a seal retainer 37 for sliding and sealing engagement with the internal walls of the liner string. External latches, which may be slip-like members 38, may be provided around the lower portion of the body 33. The central opening 34 may be provided with a frictionally engageable surface such as downwardly directed teeth 39. The liner wiper plug 15 may be initially maintained at a predetermined level within the liner string by a frangible projection 40 which engages the annular recess 14 provided in the liner string. It will be noted that the central opening 34 is engaged by the lower end of the mandrel 21 and is in fluid communication with the interior thereof. In fact, the liner wiper plug 15 may, alternatively, be connected to the mandrel 21 rather than the liner string.

As previously mentioned, a seal assembly 17 is disposed in the annular space 24 between the setting tool mandrel 21 and liner string. This seal assembly 17 may comprise a tubular body or sleeve 41 at the lower end of which is provided annular seals 42 and 43 sealingly engaging the interior 5a of the liner string and the exterior of the mandrel 21, respectively. The longitudinal distance between seals 42 and the latches 44, to be described hereafter, is critical. This dimension should be greater than the distance between the upper end of the threads 31 and the lower end of latch profile 16, for reasons to be explained hereafter.

The seal assembly 17 is initially held in position by a latch assembly, including a plurality of latches 44 which engage the corresponding latch profile 16 and the surrounding liner string. The latches 44 may be disposed in radial apertures 45 (see FIG. 8) for movement between extended positions, such as is shown in FIGS. 3 and 8, and retracted positions, such as shown in FIGS. 7 and 9. As disposed is FIG. 3, the latches 44 cannot be retracted due to the outside diameter of mandrel 21. The latches 44 may be maintained in the apertures 45 in any suitable manner. As shown in the drawings, this is accomplished by holes 46 of elongated cross-section and retainer rods or pins 47 disposed therein. It is important to notice that although the seal assembly 17 is attached to the liner string and may not move axially relative thereto, there is nothing in the seal assembly to prevent the setting tool mandrel 21 from moving axially relative to the seal assembly 17.

As seen in FIG. 1 and better shown in FIG. 4, a pumpdown plug 48 may also be utilized with the invention. Such a pumpdown plug might be provided with lip-type seals 49 for sliding and sealing engagement with the interior of the operating string 20 and the setting tool mandrel 21. The pumpdown plug 48 is also sized and adapted to engage the central opening 34 of the liner wiper plug 15. A latching device such as slips 50 may be provided for frictional engagement with the friction surfaces 39 provided in the central opening 34 to latch the pumpdown plug 48 to the liner wiper plug 15. An annular seal 51 may be provided for sealing between the pumpdown plug 48 and liner wiper plug 15.

STATEMENT OF OPERATION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1 - 9 of the drawings, operation of the preferred embodiment of the invention would proceed as follows. The liner string 1, liner wiper plug 15, seal assembly 17 and setting tool 19 would be assembled as is shown in FIG. 3 and lowered on operating string 20 into the well bore 2. After reaching the setting depth, the liner hanger would be actuated and hung in a conventional manner. Circulation would be established by pumping circulating fluid down through the operating string 20, the setting tool 19, the liner string 1 and through the liner shoe 13 into the annular space 4 surrounding the liner string 1.

After circulation is established, the setting tool 19 is then released from the liner string 1 by rotating the operating string 20 in the righthand direction to release the splined nut connector 18 as shown in FIG. 4. The operating string 20 may be lifted a few inches, such as in FIG. 6, to be sure that this release has been effected.

There is a possibility that the operating string would be lifted too much, releasing the seal assembly and displacing it upwardly so as to break the seal between the interior 5a of the liner string and seal member 42. This seal could be reestablished by again lowering the operating string until the seal member 42 reengages the liner string interior 5a. There is also a possibility, in this reengagement, that the latches 44 would hang on the threads 31. However, this would create no problem, since, as previously mentioned, the distance between latches 44 and seal 42 is greater than the distance between the upper end of threads 31 and the lower end of profile 16.

A properly measured amount of cement is then pumped into the operating string 20. At this point, the pumpdown plug 48 is placed in the operating string 20 effecting a movable seal behind the cement as it is pumped through the operating string 20, setting tool 19 and the central opening 34 of the liner wiper plug 15 into the liner string. A displacing fluid is pumped behind the pumpdown plug 48 forcing the pumpdown plug 48 into the central opening 34 and into engagement with the liner wiper plug 15 as seen in FIG. 4.

Further pressure, induced by pumping a displacing fluid behind pumpdown plug 48, will cause the frangible connection 40 between the liner wiper plug 15 and the liner string to break, releasing both the pumpdown plug 48 and liner wiper plug 15 for further movement down the liner string. The pumpdown plug and liner wiper plug are movable together, upon release of the liner wiper plug, to effect a movable seal behind the cement as the cement is displaced from the liner through the shoe 13 into the annular space 4 surrounding the liner string 1. (See FIGS. 1 and 2) Upon reaching the landing area 7, the liner wiper plug 15 lands and seats in the latch profile 11 and the latching mechanism 38 latches the liner wiper plug 15 and pumpdown plug 48 in the position shown in FIG. 2. At this point, cement should have been pumped upwardly into the annular space 4 surrounding the liner string to the desired level. The relative position of the setting tool 19 and seal assembly 17 upon termination of pumping cement is shown in FIG. 5.

It should be noted that during cementing, the force applied to the seal assembly 17 as a result of pressure within the annular space 24 is transferred to the liner string 1 and not to the setting tool 19 or operating string 20. Thus, unlike in cementing methods of the prior art, it is not necessary to maintain a great deal of weight on the operating string 20 to prevent this pressure from forcing the setting tool 19 and operating string 20 out of the liner string.

Since the seal assembly 17 is not connected directly to the mandrel 19, the mandrel 19 may be lifted or axially displaced by a limited amount without interrupting the seal between seal member 43 and the exterior of the mandrel 19. See, for example, FIG. 6 in which the setting tool 19 has been lifted a substantial amount. This may be done to check whether or not the setting tool 19 has been released from the liner hanger by disengagement of the connector means 18.

It will be noted that in either the position of FIG. 5 or FIG. 6, the seal assembly 17 is maintained in a latched in condition since the external diameter of the mandrel 21 prevents retraction of the latches 44. To release the latches 44 so that the setting tool 19 and seal assembly 17 may be removed from the liner string, the setting tool 19 is lifted still further until the reduced diameter portion 22 lies behind latches 44, allowing the latches 44 to be retracted into the released position. It will also be noted that once the reduced diameter portion 22 is in registration with the seal member 43, the seal between the sealing assembly 17 and the mandrel is broken and any liquid contained in the annular space 24a above the seal assembly 17 will be dumped.

Once the latches 44 are retracted, the seal assembly 17 is free to move upwardly with the setting tool and in fact so does when it is engaged by the centralizer lugs 23. When the seal between the seal assembly 17 and the setting tool 19 is broken, reverse circulation can be conducted, if so desired, to remove excess cement from the liner string.

After cementing is completed, the setting tool 19 and seal assembly 17 can be completely removed from the well. However, if a liner packer is utilized with the liner string, the packer would be set prior to the removal of the setting tool 19. In fact, depending upon the type of liner packer used, the setting tool 19 may be utilized in setting such a packer. There are many types of liner packers suitable for use with the present invention and since they are well known in the industry, no further discussion of liner packers will be given.

CONCLUSION

As can be seen from the description of the preferred embodiment of the invention, the apparatus and method thereof are improvements over the prior art and offer distinct advantages thereover. Probably the most apparent advantage is the removal of pressure forces which would normally be transferred from the seal assembly to the operating string. With the unique design of the present invention, these forces are transferred to the liner string and have no effect on the operating string. Thus, maintenance of great weights on the operating string during cementing is eliminated and pressure heads normally encountered in many of the prior art designs when the operating string is lifted are also eliminated. In addition, the resistance to lifting the operating string and setting tool due to the hydraulic head in the space surrounding the operating string is eliminated.

Although only one embodiment of the invention has been described herein, many variations may be made by those skilled in the art without departing from the spirit of the invention. It is therefore intended that the scope of the invention be limited only by the claims which follow.

Claims

We claim:

1. Apparatus for cementing a liner in a well bore comprising:

a. a setting tool having a tubular mandrel connected in a pipe string for extension through said liner;

b. seal means releasably attached to said liner and sealingly engaging the exterior of said mandrel and the interior of said liner permitting at least limited axial movement of said mandrel without movement of said seal means;

c. latch means included with said seal means engageable with corresponding groove means within said liner to releasably hold said seal means against axial displacement therein; and

d. said mandrel comprising a first portion and an axially spaced second portion of less diameter than said first portion, said first portion when in registration with said latch means preventing disengagement of said latch means from said groove means, said second portion when in registration with said latch means allowing disengagement of said latch means from said groove means.

2. Apparatus as set forth in claim 1 in which said sealing engagement between said seal means and said first mandrel portion is interruptable upon axial displacement of said mandrel to a position in which said seal means surrounds said second mandrel portion.

3. Apparatus as set forth in claim 1 in which said seal means comprises tubular body means, having apertures in which latch members of said latch means are mounted for radial movement between extended positions, in which said latch members engage said groove means, and retracted positions, in which said latch members are not in engagement with said groove means, said mandrel being movable between a first position engaging and holding said latch members in said extended positions, and a second position permitting said latch members to move to said retracted positions.

4. Apparatus as set forth in claim 1 in which said mandrel is provided with a plurality of radially projecting lug members for centralizing said mandrel within said liner.

5. Apparatus as set forth in claim 4 in which said lug members are engageable with said seal means upon predetermined axial displacement of said mandrel to permit removal of said mandrel and seal means from said liner.

6. Apparatus as set forth in claim 1 in which said seal means comprises a sleeve member carrying a first annular seal for sealing engagement with said liner and a second annular seal for sealing engagement with said mandrel.

7. Apparatus as set forth in claim 6 in which said latch means comprises a plurality of latch members radially movable between extended positions, in which said latch members engage said groove means, and retracted positions, in which said latch members are not in engagement with said groove means.

8. Apparatus as set forth in claim 7 in which said first annular seal is disposed below said latch members a distance greater than the distance between said groove means and any upwardly facing shoulder in said liner above said groove means capable of engagement by said latch members.

9. Apparatus as set forth in claim 7 in which said mandrel is initially attached to said liner by connector means operable upon rotation of said mandrel to release said mandrel for said limited axial movement relative to said liner.

10. Apparatus as set forth in claim 9 in which said connector means comprises threads in said liner engageable with a nut member carried by said mandrel.

11. Apparatus as set forth in claim 10 in which said first annular seal is disposed below said latch members a distance greater than the distance between said threads and said groove means.

12. Apparatus for cementing a liner in a well bore comprising:

a. a setting tool having a tubular mandrel connected in a pipe string for extension through said liner creating an annular space therebetween;

b. connector means carried by said setting tool for releasably connecting said liner thereto;

c. wiper means releasably disposed within said liner near one end of said mandrel and having a central opening through which cement may be pumped into said liner through said pipe string and mandrel;

d. plug means adapted for sliding and sealing engagement with the interior of said pipe string and mandrel effecting a movable seal behind said cement as it is pumped into said liner, said plug means being engageable with said wiper means and movable therewith, upon release of said wiper means, to effect a movable seal behind said cement as said cement is displaced from said liner into said surrounding well bore;

e. seal means disposed in said annular space comprising a sleeve member carrying first and second annular seals for sealingly engaging the interior of said liner and the exterior of said mandrel, respectively; and

f. latch means releasably connecting said seal means to said liner permitting limited axial movement of said mandrel without disturbing the axial position of said seal means.

13. Apparatus for cementing a liner in a well bore as set forth in claim 12 in which said connector means is operable by rotation of said mandrel to release said mandrel for said limited axial movement relative to said liner.

14. Apparatus as set forth in claim 12 in which said latch means comprises a plurality of latches carried by said seal means for movement from extended positions, engaging corresponding surfaces carried by said liner, to retracted positions not engaging said corresponding liner surfaces, said latches being held in said extended positions by the exterior of said mandrel preventing axial movement of said seal means relative to said liner.

15. Apparatus as set forth in claim 14 in which said first annular seal is disposed below said latches a distance greater than the distance between said connector means and said corresponding liner surfaces.

16. Apparatus as set forth in claim 14 in which said mandrel is provided with a reduced diameter portion which upon registration with said latch means by predetermined axial movement of said mandrel permits movement of said latches to said retracted positions to permit removal of said seal means from said liner.

17. Apparatus as set forth in claim 16 in which the sealing engagement of said seal means with said mandrel is interruptable by said reduced diameter mandrel portion upon less than said predetermined axial movement of said mandrel.

18. Apparatus as set forth in claim 16 in which said mandrel is provided with stop means engageable with said seal means upon further axial movement of said mandrel to remove said mandrel and seal means from said liner.

19. Apparatus as set forth in claim 18 in which said stop means comprises a plurality of radially projecting lug members centralizing said mandrel within said liner.