Title:
DOWNHOLE WELL CASING HANGER ESPECIALLY SUITABLE FOR ARCTIC ENVIRONMENT
United States Patent 3736984


Abstract:
A downhole well casing hanger apparatus especially suitable for use in arctic areas where a layer of permafrost covers the ground. The apparatus comprises a hanger unit for suspending a string of casing at a subsurface location, such as in the consolidated earth below the permafrost layer, and a combined casing landing sub-cement squeeze tool for interconnecting an upper section of casing to the hanger, for cementing the well, and also for conducting a squeezing operation on the well. The landing subsqueeze tool is connected to, and released from, the hanger unit solely by right hand rotation, which can be performed without damaging the sheath of insulation material that surrounds the section of casing that extends through the permafrost layer between the hanger and the surface.



Inventors:
GARRETT M
Application Number:
05/217023
Publication Date:
06/05/1973
Filing Date:
01/11/1972
Assignee:
FMC CORP,US
Primary Class:
Other Classes:
166/330
International Classes:
E21B34/12; E21B43/10; (IPC1-7): E21B43/10
Field of Search:
166/115,208,226
View Patent Images:
US Patent References:
3695358WELL COMPLETION SYSTEMS1972-10-03Blout
3608634HYDRAULIC SET LINER HANGER1971-09-28Cochran
3590922WASHING CEMENT FROM AROUND DISCONNECTIBLE DOWN HOLE CONNECTION1971-07-06Slack
3460615CIRCULATING CASING HANGER AND RUNNING TOOL APPARATUS1969-08-12Watkins
3420308WELL CASING HANGER1969-01-07Putch
3260309Liner cementing apparatus1966-07-12Brown



Primary Examiner:
Leppink, James A.
Claims:
What is claimed is

1. A downhole well casing hanger apparatus especially suitable for suspending casing in a well located in an Arctic environment, comprising:

2. a tubular body having at least one internal cylindrical surface,

3. annular locking groove means in said cylindrical surface,

4. first anti-rotation means for preventing relative rotation between said hanger body and an inner annular element, and

5. means for suspending the hanger body within an outer well element, and

6. a tubular body having a first outer annular groove, a second outer annular groove axially spaced from said first groove, an outer cylindrical surface intermediate said first and second grooves, and external right-hand threads around said first groove and said outer cylindrical surface,

7. an annular resilient self-contracting locking spring for selective positioning in said first and second grooves and about said outer cylindrical surface, and

8. a tubular actuator means having internal right-hand threads for cooperation with said external right-hand threads to vary the relative position of said tool body and said actuator means in an axial direction, and second anti-rotation means for cooperation with said first anti-rotation means to prevent relative rotation between said hanger body and said actuator means,

9. An apparatus according to claim 1 wherein further right-hand rotation of said tool positions said second groove opposite said locking spring, thereby facilitating contraction of said spring into said second groove and releasing said tool from said hanger unit.

10. An apparatus according to claim 1 wherein said hanger body has at least one wash port, and said tool body has at least one wash port that can be registered with said hanger body wash port when said tool and hanger unit are locked together, thereby establishing a means for conducting fluid from within said tool body to without said hanger body.

11. An apparatus according to claim 3 wherein said wash ports are located so that a first measured rotation of said tool body with respect to said hanger body locks said bodies together with said wash ports out of registration and said hanger body wash port closed a second measured rotation of said tool body brings said wash ports into registration, a third measured rotation of said tool body moves said wash ports out of registration and closes said hanger body wash port, and a fourth measured rotation of said tool body releases it from said hanger body.

12. An apparatus according to claim 4 including seal means for establishing a fluid-tight seal between said tool body and said hanger body to prevent leakage of fluid from said wash ports.

13. An apparatus according to claim 1 wherein said hanger body has an inner annular seat upon which said actuator means rests when said tool and said hanger unit are locked together, said seat and said locking ring thereby preventing axial movement of said actuator means with respect to said hanger body.

14. An apparatus according to claim 1 wherein said first anti-rotation means comprises a pin that extends inwardly from the inner cylindrical surface of the hanger body towards the axis of said hanger body, and said second anti-rotation means comprises an axial open-ended groove that accepts said pin when said tool is inserted in said hanger unit.

Description:
BACKGROUND OF THE INVENTION

This invention relates to apparatus for use in suspending pipe in a well, and more particularly for hanging a casing string in an oil or gas well at a level below the earth's surface, for extending the casing to a surface-located wellhead, for cementing the well, and for conducting a squeezing operation on the well. The general field of art to which this apparatus pertains includes classes 166 and 285 of the classification of United States patents, especially the art relating to apparatus of this type for use in wells drilled through permafrost or other unconsolidated earth formations.

The world wide search for petroleum and natural gas has led the industry to remote corners of the globe, with the result that one of the greatest potential reserves of these energy sources has been discovered beneath the permafrost covered area of the north slope region in the arctic. However, many problems have been encountered in drilling wells into these rich deposits, and in producing the relatively warm hydrocarbon fluids through the permafrost layer, for if the permafrost thaws it will subside and fail to support the wellhead and other surface structures, and also the well casing strings that are supported or hung from these structures.

Various techniques have been employed to prevent this subsidence, including covering the permafrost with a pad of gravel to insulate it from the relatively warm surface equipment, running refrigerated liquid down through the annulus between outer and inner strings of casing to maintain the temperature of the permafrost below its thawing point, supporting the surface equipment above the permafrost on large platforms that rest on long pilings frozen into the permafrost, insulating the upper section of well casing that extends through the permafrost to prevent heat in the well from thawing it, and employing a system of slip-joint casing to compensate for downdrag forces resulting from permafrost subsidence.

Although some measure of success has been achieved with these techniques, none of them provide the complete solution to the problem, and all of them are expensive to employ. The technique of insulating the upper section of casing that extends through the permafrost has been found favorable, but a prominent problem with this technique is that the insulation material is generally easily damaged. Accordingly, installation of the upper insulated casing section must be accomplished with extreme care, and one of the more important objects of this invention is to provide an apparatus for doing just that.

Another object of this invention is to provide an apparatus for landing and suspending a string of casing in a well at a remote location beneath the earth's surface.

Another object of this invention is to provide apparatus for cementing a well, and especially one that has been drilled in a permafrost covered area.

Still another object of this invention is to provide apparatus for conducting a squeeze operation on a well, particularly one located in a permafrost region.

Yet another object of the present invention is to provide apparatus for facilitating removal of a casing sheathed with insulation from a well, as for servicing or replacement, without incurring substantial damage to the insulation.

SUMMARY OF THE INVENTION

The present invention comprises a well casing hanger apparatus with a hanger unit adapted for suspending a string of casing in the well at a remote downhole location, and a combined landing sub-cement squeeze tool that provides a means for landing the hanger unit, for connecting and disconnecting an insulated upper string of casing to the hanger without damage to the insulation, for cementing the well, and for squeezing the well. The hanger unit is provided with wash ports which register with corresponding wash ports in the landing sub-cement squeeze tool when the tool and hanger unit are in a certain positional relationship, and the tool has a lock ring that is caused to move into or out of a complementary locking groove in the hanger unit to connect or disconnect the tool and the unit. The tool and hanger unit can be run as an assembly, or the hanger unit can be run and landed first and then the tool and the insulated casing or running string to which it is attached can be run and connected to it. Right hand rotation of the tool is all that is necessary to facilitate its connection to, and its release from, the hanger unit, and also to position the tool in the hanger unit for cementing or squeezing the well.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of the apparatus of this invention installed in a well that has been drilled through a permafrost formation, and that has an insulated upper casing section extending through the permafrost layer.

FIG. 2 is an enlarged view of the apparatus of this invention, with a portion thereof shown in longitudinal section to better illustrate the internal configuration of the elements, showing the landing sub-squeeze tool in the hanger unit but not yet locked thereto.

FIG. 3 is a view like FIG. 2, showing the relative positions of the elements after the landing subsqueeze tool has been rotated and locked into the hanger unit.

FIG. 4 is a view like FIG. 3, showing the relative positions of the elements following further rotation of the landing sub-squeeze tool into the position for washing out excess cement from the well following a cementing procedure.

FIG. 5 is a view like FIG. 4, showing the relative positions of the elements following further rotation of the landing sub-squeeze tool to close the wash ports in the hanger unit.

FIG. 6 is a view like FIG. 5, showing the relative position of the elements following further rotation of the landing sub-squeeze tool to release it from the hanger unit in preparation for withdrawal from the well.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIG. 1 of the drawings, the downhole well casing hanger apparatus 10 of the present invention comprises a hanger unit 12 internally threaded or otherwise adapted at its lower end for connection to a lower section 14L of an inner well casing 14, and a combined landing sub-cement squeeze tool 16 also internally threaded or otherwise adapted at its upper end for connection to an upper section 14U of the well casing 14. As used in a well that has been drilled through a permafrost layer 20 overlying a consolidated earth formation 22, and then lined with an outer or surface casing 24 extending down from a surface located wellhead 26, the hanger unit 12 is landed in and suspended from the outer casing 24 at a suitable location in the consolidated earth formation 22 below the bottom of the permafrost layer 20. Thus, the hanger unit 12 and the lower casing section 14L are supported at a level beneath that where subsidence may occur, and where the earth is sufficiently firm to provide the needed structural strength for support of the inner casing 14.

As is illustrated in FIG. 1, the upper casing section 14U is surrounded by a sheath 28 of insulation, so that the heat in the well between the consolidated formation 22 and the surface is prevented from affecting the surrounding permafrost. Accordingly, the structural strength of the permafrost required to adequately support the surface wellhead equipment, etc., is maintained intact.

Referring now to FIGS. 2-6 for purposes of illustrating the details of the hanger unit 12 and its cooperating landing sub-cement squeeze tool 16, it is seen that the hanger unit includes a tubular body 30, a resilient self-expandable split hanger ring 32 circumscribing the body 30, a shear ring 34 surrounding the body above the hanger ring 32, and a plurality of frangible shear pins 36 that releasably hold the shear ring 34 in position on the body 30. The hanger ring 32 has a plurality of upstanding, rigid finger-like segments 32a, 32b, 32c, etc., that serve to engage a complementary shaped groove system of an outer well element, as shown in FIG. 1, to support the hanger unit in that element, all in the well-known conventional manner as is fully described in detail in U.S. Pat. No. 3,420,308 to Samuel W. Putch, issued on Jan. 7, 1969. Although this type of hanger support system is preferred for purposes of illustrating the present invention, it should be understood that other hanger support systems can be substituted for this split ring system without departing from the spirit of the invention.

The lower end portion 30a of the hanger body 30 is provided with internal threads 30b for connecting the hanger to the upper end of the lower casing section 14L. The hanger body 30 has a lower inner cylindrical surface 38 with an annular groove 40, and the surface 38 is relieved above the groove to form an upwardly facing stop shoulder 42, the groove and the stop shoulder providing landing means for suspending another string of casing, etc., inside the hanger body by means of another hanger of this same type. It should be understood, however, that the surface 38 may be provided with other configurations, or may have no grooves or shoulders, as desired.

Above the area of the groove 40 and stop shoulder 42 the hanger body 30 has an intermediate inner cylindrical surface 46 of a diameter in the illustrated embodiment greater than the diameter of the surface 38, and above the surface 46 an upper inner cylindrical surface 48 with a diameter greater than that of the surface 46. Interconnecting the surfaces 46, 48 is an upwardly and outwardly sloping annular stop shoulder 50, and just above that top shoulder an anti-rotation pin 52 extends significantly past the surface 48 towards the axis of the hanger body 30. As will be more fully explained later, the stop shoulder 50 affords a seat for the landing sub-cement squeeze tool 16, and the anti-rotation pin 52 cooperates with the tool 16 in connecting and releasing it from the hanger unit.

Spaced axially above the anti-rotation pin 52 is an annular groove system 54 in the surface 48 that cooperates with the tool 16 for locking and unlocking it to the hanger body 30, as will be later described in detail. A plurality of wash ports 56 extend through the wall of the hanger body 30 at a location above the groove system 54, these wash ports 56 cooperating with the tool 16 when it is used for cementing the well.

The landing sub-cement squeeze tool 16 includes a tubular body 60, an axially split resilient self-contracting annular lock spring 62, and a tubular lock spring actuator nut 64 with internal right hand threads 64a that cooperate with external right hand threads 60a on the tool body 60. The lower end of the actuator nut 64 is provided with an external axially-extending anti-rotation groove 66 that accepts the anti-rotation pin 52 and cooperates with it to prevent rotation of the actuator nut with respect to the hanger body 30 when the pin and groove are in registration. Accordingly, when the tool body 60 is rotated to the right, the actuator nut remains stationary with the hanger body 30 and the tool body 60 moves downwardly with respect to both the actuator nut and the hanger unit.

The split lock spring 62 normally resides in an annular groove 68 extending around the external surface of the tool body 60. The tool body 60 has a cylindrical surface 70 spaced axially from the groove 68, and above it when the tool 16 is oriented vertically in its functional position as illustrated in the drawings, and this surface 70 has a diameter greater than the groove 68. An upwardly and outwardly sloping annular cam shoulder 72 interconnects the groove 68 with the annular surface 70. Spaced axially and upwardly from the surface 70 is another groove 73 having a diameter the same as that of groove 68, and interconnecting the surface 70 and the groove 73 is an upwardly and inwardly sloping annular surface 74.

The diameters of the grooves 68,73, the annular surface 70, the hanger body surfaces 46, 48 and the radial dimension of the lock spring 62 are so interrelated that when the lock spring is in either the groove 68 (FIG. 2) or the groove 73 (FIG. 6) the spring will pass freely into and out of the hanger body 30, thereby facilitating insertion of the tool 16 into, and withdrawal of it from, the hanger 12 without restriction. However, when the spring 62 is in the groove system 54 and the tool body 60 is positioned so that its surface 70 is within the spring, the spring is locked into the groove system 54, thereby preventing upward movement of the actuator nut 64. Furthermore, since the annular seat 50 prevents downward movement of the nut 64, the nut is secured against axial movement in either direction when the spring 62 is in the grooves 54.

Because of the threaded connection between the actuator nut 64 and the tool body 60, when the nut is held by the spring 62 the tool body also can not move axially unless it is rotated, and thus the tool 17 is effectively locked into the hanger unit 12 when the spring is in the grooves 54. Accordingly, from the conditions illustrated in FIG. 2 wherein the tool 16 is landed in the hanger unit 12 but not locked thereto, rotation of the tool body 60 to the right will cause the body to be threaded downwardly inside the actuator nut 64, and as this movement occurs the annular cam surface 72 causes the lock spring 62 to expand into the groove system 54. Continued right hand rotation of the tool body 16 moves the surface 70 behind the lock spring 62 to lock the spring into the groove system 54, and of course lock the tool 16 into the hanger unit 12, as illustrated in FIGS. 3-5. When the tool body 60 is further rotated to the right from the position illustrated in FIG. 5, the body moves downwardly with respect to the actuator nut 64 and the hanger body 30, and when the groove 73 reaches a position opposite the spring 62 the spring contracts out of the groove system 54 into the groove 73, releasing its locking hold on the hanger body 30 and thereby releasing the tool 16 from the hanger unit 12. The tool 16 can then be withdrawn from the hanger unit 12 and retrieved from the well merely by lifting the upper casing section 14U.

As is apparent from the foregoing description, the apparatus of the present invention is ideally suited to landing and releasably locking two sections of casing together in a remote location in a well, and particularly for interconnecting an upper casing section, such as 14U that is surrounded by a delicate sheath of insulation, to a lower casing section, such as 14L. No manipulation other than simple right hand rotation of the tool 16 with respect to the hanger unit 12 is required in order to accomplish the foregoing, and hence any damage that the insulation might incur is of minimal extent.

When the landing sub-cement squeeze tool 16 is to be used as a landing sub for the lower casing section 14L, the hanger unit 12 and the tool 16 are made up at the surface into the position shown in FIG. 3, run and landed in the outer casing's sub 24a by means of drill pipe 78 or other suitable running string, and then cemented through in this position. The tool body 60 is then rotated to the right, by rotation of the drill pipe 78 at the surface, until its plurality of circumferentially spaced wash ports 80 register with the wash ports 56 in the hanger body 30 (FIG. 4). The cement in the annulus between the outer casing 24 and the drill pipe 78 is then washed out between the hanger and the surface, the annular seals 82,84,86 and 88 assuring fluid-tight integrity between the tool body 60 and the hanger body 30. The tool body 60 is then further rotated to the right until it arrives in the position illustrated in FIG. 6, allowing the lock spring 62 to contract into the groove 73. This releases the tool 16 from the hanger unit 12 and the tool is then retrieved.

If the cement job is not satisfactory, this invention provides the operator with the option of doing a cement squeeze job with this same equipment. To carry out this operation, the well is reentered with the tool 16 in the condition illustrated in FIG. 2, i.e., with the locking spring 62 contracted into the groove 68. The tool body 60 is then rotated to the right to move the body downward until the cylindrical surface 70 is positioned within the spring 62, thereby expanding the spring into the groove system 54 and locking the tool to the hanger unit as shown in FIG. 3. The lower casing section 14L is then perforated in the weak area and cement pumped down through the drill pipe 78 and the perforations (not shown) into the annulus between the casing and the well. The drill pipe 78 is then rotated further to the right to lower the tool body 60 into the position shown in FIG. 6, allowing the locking spring 62 to contract into the groove 73 and releasing the tool 16 from the hanger unit 12. The tool 16 can then be retrieved from the well, and the lock spring 62 returned to the groove 68 to prepare the tool 16 for use in running and connecting the upper casing section 14U to the lower section 14L.

It should be noted that during right hand rotation of the drill pipe 78 to move the tool body 60 from the FIG. 3 to the FIG. 6 position, the tool body goes through the normal wash position illustrated in FIG. 4, thereby providing the operator with the option of either stopping at this wash position and washing or continuing rotation through it to the release position shown in FIG. 6. Accordingly, a high degree of versatility is provided with the unique combination of hanger unit and landing subsqueeze tool of this invention.

As is by now readily apparent, the upper casing section 14U can easily be run and connected to the lower section 14L by securing it to the tool 16, running and landing the tool in the hanger unit 12, and rotating the tool body 60 until it moves downward into the position shown in FIG. 3. If, for any reason, removal of the upper casing section 14U is required, the tool body 60 is merely rotated further to the right until the groove 73 is positioned within the lock spring 62, allowing the lock spring to contract into the groove and release the tool from the hanger unit 12. The casing section 14U can then be withdrawn from the well.

In order to insure that the desired positioning of the tool body 60 in the hanger body 30 has been achieved when the drill pipe 78 or the upper casing section 14U has been rotated to the right, the spacings of the grooves 68, 73, and of the wash ports 56, 80 are coordinated with the right hand thread system 60a, 64a, between the tool body 60 and the actuator nut 64 so that a given number of revolutions will move the tool body 60 a certain distance downwardly in the hanger body 30. As an example, if these spacings and dimensions are established so that nine rotations are required to move the tool body 60 from the position of FIG. 2 into the position of FIG. 3, nine more rotations to move from the position of FIG. 3 into the FIG. 4 position, nine additional rotations to move from the position of FIG. 4 into the FIG. 5 position, and ten more rotations to move the tool body from the FIG. 5 position into the release position of FIG. 6, the results have been found very satisfactory. Of course, it is to be understood that other schedules of rotations between the several positions can be established if desired.

Although the best mode contemplated for carrying our the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.