US3667547A - Method of cementing a casing string in a well bore and hanging it in a subsea wellhead - Google Patents

Abstract

Method of cementing a casing string in a well bore and hanging it in a subsea wellhead, a safety joint being incorporated in the string below a casing hanger secured to the latter, enabling the joint to be disconnected, in the event the casing string sticks in the well bore during its reciprocation while being cemented, and the casing string above the joint and the casing hanger removed. An extension tool secured to the lower end of a length of casing string is attached to the casing hanger and spaced therefrom a distance corresponding to the distance between the wellhead and upper end of the casing string cemented in the well bore, and is lowered to place the tool over such upper end, with the hanger landed in the wellhead, after which the casing string cemented in placed is pulled upwardly into and secured to the extension tool by slips of the tool.

Description

United States Patent Ahlstone 1 June 6, 1972 Arthur G. Ahlstone, Ventura, Calif.

Vetco Offshore Industries, Inc., Ventura, Calif.

[22] Filed: Aug. 26, 1970 [21] Appl.No.: 67,005

[72] Inventor:

[73] Assignee:

[56] References Cited UNlTED STATES PATENTS 3,163,217 12/1964 Haeber ..166/277X 2,305,261 12/1942 Kinley ..166/301X OTHER PUBLICATIONS Oil-Well Cementing Practices in the United States, N.Y. Am.

Pet. Inst., 1959, pp. 106, 107 Uren, Lester C. Petroleum Production Engineering; Oil Field Development, N.Y., McGraw-Hill, 1956, pp. 433, 541

Primary Examiner-James A. Leppink Attorney-Bemard Kriegel [5 7] ABSTRACT Method of cementing a casing string in a well bore and hanging it in a subsea wellhead, a safety joint being incorporated in the string below a casing hanger secured to the latter, enabling the joint to be disconnected, in the event the casing string sticks in the well bore during its reciprocation while being cemented, and the casing string above the joint and the casing hanger removed. An extension tool secured to the lower end of a length of casing string is attached to the casing hanger and spaced therefrom a distance corresponding to the distance between the wellhead and upper end of the casing string cemented in the well bore, and is lowered to place the tool over such upper end, with the hanger landed in the wellhead, after which the casing string cemented in placed is pulled upwardly into and secured to the extension tool by slips of the tool.

5 Claims, 9 Drawing Figures METHOD OF CEMENTING A CASING STRING IN A WELL BORE AND HANGING IT IN A SUBSEA WELLHEAD The present invention relates to well bore methods, and more particularly to a method of securing a casing string in a subsea well bore and of landing the casing hanger in a subsea wellhead.

In drilling well bores on land, it is desirable to reciprocate the casing during the cementing operation to secure a better cement bond to the casing and prevent channeling of the cement in the annulus surrounding the well casing. After all of the cement has been pumped into place, the casing string is held stationary while the cement sets up. Thereafter, a sliptype casing hanger is placed around the casing string to support the casing and seal against it. The slip-type casing hanger makes it possible to support and seal the casing at any point along its upper portion, regardless of the fact that the casing might stick at any time during its reciprocation.

On wells drilled from floating drilling vessels, which use subsea wellheads on or near the ocean bottom, reciprocation has not been used heretofore because of the casing sticking problem, and the fact that subsea casing hangers are secured to the casing string at its upper end and lowered with the casing toward a landing shoulder in a wellhead housing. If the casing string sticks during its reciprocation, the casing hanger will be located above the wellhead landing shoulder and cannot be lowered into engagement therewith. If the subsea casing hanger does not land on the wellhead shoulder or seat, then stack-up and space-out problems occur. In addition, the casing string might be put into compression, involving a very dangerous situation. If the casing string sticks during the running in of the casing hanger, with the casing hanger above its associated seat in the wellhead, expensive and time consuming operations are required to effect correction. Thus, the casing must be cut off accurately in the area just above the wellhead housing. The cutofi casing hanger, running tool and running string are recovered from the well. A dressing mill is run into the well to prepare the top of the cutoff casing so that a special emergency slip-type casing hanger can be run into the wellhead housing and landed in place. A casing spear is lowered inside the cutoff casing string vto place it in tension in the slip assembly of the special emergency slip-type casing hanger. The casing spear and its running string are removed, after which the seal of the special emergency slip-type casing hanger is actuated, followed by recovery of the running string. The stub of easing sticking above the special emergency sliptype casing hanger is then cut off accurately and such stub of easing, the cutting tool and its running string removed.

With the present invention, a method is provided that allows the overall length of the casing string to be appropriately shortened in the event of the casing sticking in the well bore, with the casing hanger located above its normal seating position in the wellhead. This objective is accomplished by enabling the casing string to be disconnected at a convenient distance below the casing hanger and removed. This pennits the casing hanger to be secured to a shorter length of casing string and lowered in the well bore and appropriately related to the main portion ofthe casing string remaining in the well bore, with assurance that the casing hanger is landed in the subsea wellhead. The casing string is then pulled upwardly into sealed and supporting relation to the lower part of the casing string thereabove.

As a result of the foregoing method, substantial savings in cost and time are effected. Assurance is also had that the easing string will be in tension, rather than in compression, within the well bore.

In general, an object of the invention is to provide a method of readily shortening the overall length of the casing string, to secure proper hanging of the casing hanger in the wellhead, and to eliminate the problems previously associated with the sticking of the casing during its reciprocation.

This invention possesses many other advantages and has other objects which may be made more clearly apparent from a consideration of a method embodying the invention. This method is shown and described in the present specification in connection with the drawings accompanying and constituting a part thereof. Such drawings and method will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken ina limiting sense.

REFERRING TO THE DRAWINGS FIG. 1 is a diagrammatic view of a subsea well bore, with a casing string therein, and within a marine riser extending from a wellhead housing to a floating drilling vessel at the top of the ocean, or other body of water;

FIG. 2 is a diagrammatic view of a casing string being reciprocated during its cementing operation;

FIG. 3 is a diagrammatic view illustrating the lower main portion of a cemented casing string stuck in the well bore, with the casing hanger above the wellhead, and with a string shot being run for releasing a safety joint in the casing string; FIG. 4 is a view of the equipment disclosed in FIG. 3, with the casing hanger and the casing string above the safety joint removed;

FIG. 5 is a view illustrating an extension tool at the lower end of an emergency casing string telescoped over the upper end of the stuck casing, with the casing hanger landed in its seat in the wellhead;

FIG. 6 is a view similar to FIG. 5, illustrating the upper portion of the stuck casing string being pulled upwardly within the extension tool;

FIG. 7 is a view of the completed operation, with the casing spear and the associated running string removed, and with the hanger disposed on its seat in the wellhead to hold the casing string in tension;

FIG. 8 is an enlarged longitudinal section, a portion being disclosed in side elevation, of the safety joint portion of the original casing string;

FIG. 9 is a longitudinal section, with a portion shown in side elevation, of the extension tool telescoped over the upper end of a lower casing string to support the latter and to be sealed off with respect thereto, the extension tool being in the condition illustrated in FIG. 7.

As illustrated in the drawings, awell bore 10 has been drilled into aformation 11 underlying a body ofwater 12, such as an ocean, through use of a vessel 13 floating above the well bore, asuitable subsea wellhead 14 being disposed at the ocean floor and supporting anouter casing string 15 previously installed in the well bore and cemented in place. A suitablemarine riser 16 extends between the subsea wellhead l4 and the floating vessel 13, and through which various operations in drilling the well bore, cementing casing therein, and perfomiing other operations, occur.

As disclosed in the diagrammatic views in FIGS. 2 to 7, inclusive, the well bore 10 has been drilled below the lower end of theouter casing string 15. It is desired to run aninner casing string 17 into such well bore to a predetermined depth, cement such casing string in place, and support thecasing string 17 by means of acasing hanger 18 secured to its lower end and landed on aseat 19 in thesubsea wellhead 14, and which may be latched in place by a suitablehanger lock ring 20. Thering 20 may be a split inherently contractable lock ring mounted in an internalcircumferential groove 21 in the wellhead and having a downwardly taperingsurface 22 for. engagement by thecasing hanger 18 to be expanded outwardly within itsgroove 21 until the hanger lands on thewellhead seat 19, whereupon v the lock ring will contract inherently over an upwardly facingcasing hanger shoulder 23, to retain the hanger in thewellhead 14, in a known manner.

The string ofcasing 17 to be disposed within the well bore has its upper end suitably secured to thecasing hanger 18, which,'in turn, is releasably attached to a runningtool 24 secured to a runningstring 25 that extends through theriser 16 to the drilling vessel 13. Normally,the casing string is lowered through the marine riser and into the well bore 10.

Thecasing hanger 18 is connected to the uppermost casing joint and to the runningtool 24 attached to the runningstring 25, lowering of the casing string being continued until the casing hanger is adjacent to the wellhead l4. Circulation is then established down through the runningstring 25 and thecasing string 17 to condition the well bore, after which the required charge of cement slurry is pumped down through the running string and the casing string to discharge from the lower end, or other predetermined point, of the latter, and for upward passage around the casing string to a desired elevation in the well bore. During the pumping of fluid and cement slurry through the casing string and out of thecasing string 17, the latter is reciprocated to prevent channelling of the cement in theannulus 26 surrounding the casing string, and to secure a better bond between the casing string and the wall of the surrounding well bore. After the desired amount of cement slurry has been pumped out of the casing string, thehanger 18 is lowered into engagement with itsseat 19, the cement setting up and hardening around the casing string.

At times, thecasing string 17 may stick in the well bore, leaving thecasing hanger 18 disposed above thesubsea wellhead 14, which introduces the difficult situation hereinabove described. 7

To enable thecasing hanger 18 to be landed on itsseat 19, and thecasing string 17 placed in tension in the event it becomes stuck in the well bore, asafety joint 30 is incorporated in the casing string at a desirable distance below thewellhead 14. In the event of the casing string sticking in the well bore, the runningstring 25,casing hanger 18 andupper portion 17a of the casing string can be released at the safety joint from the lower portion 17b of the casing string and withdrawn through themarine riser 16 to the drilling vessel 13.

The safety joint includes an elongate innertubular member 31, the lower end of which is threadedly secured to an adjacent casing section 17b, such inner tubular member having a left-hand threadedpin 32 on its lower portion above which the tubular member has a smooth, externalcylindrical surface 33 extending to a smoothtapered surface 34 at the upper terminal portion of the inner member. The safety joint further includes an elongateouter member 35 having a lower box 36 provided with a left-hand thread 37 mating with thepin thread 32 and having an internal smoothcylindrical surface 38, the upper end of which terminates at an upwardly taperinginner surface 39 companion to the uppertapered surface 34 of the inner member. When the threadedportions 32, 37 of the joint are fully engaged, thesetapered surfaces 34, 39 contact one another to provide a metallic seal between the inner and outer members. As further assurance against leakage between the inner and outer tubular members, anelastomer side seal 40 may be provided in agroove 41 in the outer member, engaging thetapered surface 34 of the inner member. The inner and outer members are of any suitable length, being, for example, about to 12 feet in length from the upper ends of theirthreads 32, 37 to their taperedseal portions 34, 39.

Thesafety joint 30 is incorporated in the casing string, as described above. If reciprocation of thecasing string 17 does not result in its sticking, thecasing hanger 18 is landed and locked in place in thesubsea wellhead 14, after which the runningtool 24 can be released from thecasing hanger 18 and elevated on the runningstring 25 to the drilling vessel. If, however, the casing string sticks so that thehanger 18 does not reach itscompanion seat 19 in the wellhead, it is necessary to shorten the overall length of thecasing string 17. A string shot (FIG. 3) is lowered on asuitable wireline 45 through the runningstring 25 into the casing, and is set off within the threadedportion 32, 37 of thesafety joint 30, while right-hand torque is applied by the running string to rotate theupper por tion 17a of the casing string and theouter member 35 relative to theinner member 31, to unthread the outer member from the inner member and allow theouter portion 35 of the safety joint, together with thecasing string portion 17a, casinghanger 18, runningtool 24 and runningstring 25, to be recovered through themarine riser 16 to the drilling vessel, the main lower portion 17b of the casing string remaining cemented in the well bore, as illustrated diagrammatically in FIG. 4.

Theouter portion 35 of the casing safety joint is removed from the lower end of theupper portion 17a of the casing string, and an extension tool (FIG. 9) threaded on the bottom of the latter, an appropriate length of casing 170 being provided between theextension tool 50 and thecasing hanger 18 to correspond to the distance between the upper end of the casing 17b cemented in the well bore and theseat 19 in thewellhead 14, such that the lowering of the substitute casing string or casing string extension 170 will effect landing of the casing hanger on the wellhead seat and telescoping of theextension tool 50 partially over theinner tubular member 31 of the safety joint. 7

Theextension tool 50 is secured to the lower end of thecasing string extension 17c, the upper end of which is attached to thecasing hanger 18, which, in turn, is secured to a runningtool 24 attached to the runningstring 25, and lowered through themarine riser 16. The extension tool is telescoped over the upper portion of theinner tubular member 31 of the safety joint portion, whereupon thecasing hanger 18 engages itscompanion wellhead seat 19. The extension tool (FIG. 9) includes anouter body 51 having an elongate internalcircumferential groove 52 therein, in which asplit slip ring 53 is disposed having inner upwardly facingteeth 54 adapted to grip thecylindrical surface 33 of theinner tubular member 31. The slip ring also has a downwardly taperingexternal expander surface 55 engaging a companion internal taperedsurface 56 in anexpander 57 embraced by the inner wall orbase 58 of thebody groove 52. The lower end of the expander bears against the upper end of a stack of metallic frusto-conical seal rings 59 inclined in an upward and inward direction, the lower one of which bears against a back-upring 60 resting upon abody shoulder 61 defining the lower end of theelongate groove 52.

When thecasing hanger 18 is landed on itsseat 19, theouter body 51 is telescoped over the uppercylindrical portion 31 of theinner tubular member 30, as disclosed diagrammatically in FIG. 5. A casing spear of a known type is then secured to atubing tension string 71 and lowered down through the runningstring 25 until the spear is located within theinner tubular member 31. An upward pull is now taken on thetension string 71, such pull causing the casing spear to grip theinner tubular member 31 and exert an upward pull on the lower casing string 17b, stretching the latter and moving the elongate innertubular member 31 upwardly within theouter body 51 of theextension tool 50, and to a position in which the upper end of the safety joint member is disposed above the slip ring 53 (FIG. 6). Relaxation of the tension on thetubing string 71 andcasing spear 70 will cause the lower casing string 17b to tend to contract. However, thecylindrical surface 33 of theinner member 31 will be gripped by theteeth 54 of the slip ring, tending to shift the latter downwardly within theexpander 57, the coengaging taperedsurfaces 55, 56 forcing the teeth more firmly into the periphery of the inner tubular member. The downward force, resulting from the tension in the lower casing string, will be transmitted from theexpander 57 to the inclined metal seal rings 59, expanding the latter in inward and outward directions against thecylindrical periphery 33 of theinner tubular member 31 and thecylindrical base 58 of the groove, thus effectively sealing theouter body 51 with respect to theinner tubular member 31.

Thecasing spear 70 is now removed (FIG. 7), the lower casing section 17b continuously exerting a pull upon the casing string extension 17b through theslip 53,expander 57, seal rings 59 andouter body 51, this pull being transferred through thecasing hanger 18 to the shoulder orseat 19 within thewellhead 14. The effective length of thecasing string 17 has been restored, with thehanger 18 appropriately landed in thewellhead 14, and with thecasing string 17 held in tension.

Thecasing hanger 18 can now be pressure tested in a known manner. If appropriately sealed in thewellhead 14, the runningtool 24 is released and removed with the runningstring 25 through themarine riser 16 to the drilling vessel 13. Subsequent operations can now be performed in the usual manner.

I claim:

1. A method of hanging a well bore casing string from a wellhead, comprising providing a releasable threaded connection in the casing string at a predetermined location, said threaded connection comprising a lower inner tubular member forming the upper part of a lower portion of the easing string and threadedly connected to an upper outer tubular member forming the lower part of an upper portion of the easing string, lowering the casing string in the well bore, releasing the connection by rotating the upper portion of the casing string relative to the lower portion to unthread the upper outer tubular member from the lower inner tubular member, elevating the upper portion of the casing string from the well bore with the lower portion of the casing string remaining in the well bore, lowering a casing string extension in the well bore with an extension tool secured to its lower end and a casing hanger secured to its upper end, such casing string extension being of a predetermined length and being lowered until said extension tool telescopes over the periphery of said lower inner tubular member of said lower portion of the casing string and said hanger lands in the wellhead, and pulling the upper part of said lower casing string portion upwardly to shift said inner tubular member upwardly within said extension tool, said tool embodying gripping means which engages the periphery of said inner tubular member to prevent its movement downwardly of the extension tool, whereby said casing string extension and lower portion of the casing string are maintained in tension with the hanger landed in the wellhead' 2. A method as defined inclaim 1; cementing the casing string in the well bore prior to release of the connection, and reciprocating the casing string in the well bore during the cementing operation 3. A method as defined inclaim 1; said threaded connection between said inner and outer tubular members being left hand.

4. A method as defined inclaim 1; said casing string extension being lowered in the well bore on a first tubular running string releasably secured to the casing hanger, upward pulling of the upper part of said lower casing string portion being effected by lowering a spear through the running string and the casing string extension on a second running string, securing said spear to said upper part, pulling upwardly on the second running string, releasing the spear and removing the spear and second running string through the casing string extension and first running string, and then releasing said first running string from the casing hanger.

5. A method as defined in claim 4; firing a string shot lowered into the releasable connection to facilitate release of the connection upon rotation of the casing string above the connection, cementing the casing string in the well bore prior to release of the connection, and reciprocating the casing string in the well bore during the cementing operation.

Claims (5)

1. A method of hanging a well bore casing string from a wellhead, comprising providing a releasable threaded connection in the casing string at a predetermined location, said threaded connection comprising a lower inner tubular member forming the upper part of a lower portion of the casing string and threadedly connected to an upper outer tubular member forming the lower part of an upper portion of the casing string, lowering the casing string in the well bore, releasing the connection by rotating the upper portion of the casing string relative to the lower portion to unthread the upper outer tubular member from the lower inner tubular member, elevating the upper portion of the casing string from the well bore with the lower portion of the casing string remaining in the well bore, lowering a casing string extension in the well bore with an extension tool secured to its lower end and a casing hanger secured to its upper end, such casing string extension being of a predetermined length and being lowered until said extension tool telescopes over the periphery of said lower inner tubular member of said lower portion of the casing string and said hanger lands in the wellhead, and pulling the upper part of said lower casing string portion upwardly to shift said inner tubular member upwardly within said extension tool, said tool embodying gripping means which engages the periphery of said inner tubular member to prevent its movement downwardly of the extension tool, whereby said casing string extension and lower portion of the casing string are maintained in tension with the hanger landed in the wellhead.

2. A method as defined in claim 1; cementing the casing string in the well bore prior to release of the connection, and reciprocating the casing string in the well bore during the cementing operation.

3. A method as defined in claim 1; said threaded connection between said inner and outer tubular members being left hand.

4. A method as defined in claim 1; said casing string extension being lowered in the well bore on a first tubular running string releasably secured to the casing hanger, upward pulling of the upper part of said lower casing string portion being effected by lowering a spear through the running string and the casing string extension on a second running string, securing said spear to said upper part, pulling upwardly on the second running string, releasing the spear and removing the spear and second running string through the casing string extension and first running string, and then releasing said first running string from the casing hanger.

5. A method as defined in claim 4; firing a string shot lowered into the releasable connection to facilitate release of the connection upon rotation of the casing string above the connection, cementing the casing string in the well bore prior to release of the connection, and reciprocating the casing string in the well bore during the cementing operation.

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