US3592489A

US3592489A - Housings with contractable well casing hanger seats

Info

Publication number: US3592489A
Application number: US807730A
Authority: US
Inventors: Benton F Baugh; Bobby H Nelson; Carl F Huntsinger
Original assignee: Vetco Offshore Industries Inc
Current assignee: Vetco Gray LLC
Priority date: 1969-03-17
Filing date: 1969-03-17
Publication date: 1971-07-13
Anticipated expiration: 1988-07-13
Also published as: JPS496963B1; DE1963605A1; GB1250039A; FR2033698A5

Abstract

A housing having a seat for a casing hanger, which seat is initially in an outer or expanded position to avoid restrictions projecting into the housing. Fluid pressure acts on a piston device to effect contraction or constriction of the seat, causing it to project into the housing and serve as a landing shoulder for a casing hanger.

Description

United States Patent [72] Inventors Benton F. Baugh;

Bobby H. Nelson, Houston, Tex.; Carl F. Huntsinger, Ojai, Calif. [21) Appl. No. 807,730 [22] Filed Mar. 17, 1969 [45] Patented July 13, 1971 [73] Assignee Vetco Offshore Industries, Inc.

Ventura, Calif.

[54] HOUSINGS WITH CONTRACTABLE WELL CASING HANGER SEATS 20 Claims, 6 Drawing Figs.

[52] US. Cl 285/18, 285/141, 285/315, 285/321 [51] Int. Cl F161 55/00 {50] Field of Search 166/06, 86, 88; 285/18, 141, 315, 321

h [56] Referenos Cited UNITED STATES PATENTS 2,086,431 7/1937 Penick et a1. 285/141 Watkins Blackman et al.

Knox 1.

Fowler Putch Brown FOREIGN PATENTS Great Britain Primary Examiner-Dave W. Arola Attorney-Bernard Kreiegel 285/315 X 287/135 285/315 X 285/141 X 285/18 285/18 PATENTEDJUL] 3m 35924 9 HGI INVENTOR MICHAEL SIMON 47 ATTORNEYS ll llOUSllNGS WITH CONTRACTABLE WELL CASING HANGER SEATS The present invention relates to well bore apparatus, and more particularly to apparatus for hanging casings from a housing at the top of the well bore.

Present housings for hanging casing string in well bores, particularly those employed in offshore drilling, have a landing shoulder that reduces the bore diameter through the housing to a substantial extent. This requires the well bore to be underreamed before the desired diameter of easing can be run through the housing into the well bore and supported properly from the housing. ln the absence of underreaming, it has been necessary to run smaller casing through the housing and into the well bore than the desired size.

The foregoing difficulties are solved by virtue of the present invention. The casing hanger seat is initially carried in the housing in an outer or expanded condition, thus effecting only a slight restriction, if any, through the housing passage, and thereby allowing a hole opener of an appropriate diameter to be run with the customary well drilling bit. Accordingly, a well bore diameter is drilled that is large enough to permit running of the desired diameter of easing through the housing and into the well bore, the casing being of a larger diameter than was heretofore obtained when underreaming was not performed.

Following the drilling of the hole to the desired larger diameter, the hanger seat is contracted or constricted to the required seat diameter to provide a landing shoulder through which the desired diameter of easing can be run and on which the hanger body can be landed for the purpose of supporting the well ca ing in the well bore. With the casing so supported, it can be cemented in place, appropriate circulating fluid being bypassed around the constricted hanger seat until the bypass passage is to be closed by devices that, per se, constitute no part of the present invention.

The hanger seat can be positively locked in its contracted or constricted position. It can be contracted or constricted hydraulically to form a rigid landing shoulder. After the seat has been constricted, the apparatus is so constructed and arranged that the well bore pressure cannot shift the contracted seat from its constricted position projecting into the well head housing.

For the purpose of reducing the stresses in the seat, it can be made of a composite construction, such as an inner ring and an outer ring, for the purpose of allowing standard materials to be used and to reduce the force required to effect constriction of the inner and outer rings to the desired internal diameter.

This invention possesses many other advantages, and has other purposes which may be made more clearly apparent from a consideration of several fonns in which it may be embodied. Such forms are shown in the drawings accompanying and forming part of the present specification. These forms 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 in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

FIG. 1 is a longitudinal section through an embodiment of the apparatus, with its hanger seat in expanded condition;

FlG. 2 is a view similar to FIG. 1, with the seat contracted;

FIG. 3 is an enlarged fragmentary longitudinal section through a portion of the apparatus of FIG. I, disclosing the seat in expanded condition;

FIG. 4 is a view like FIG. 3, illustrating the seat in the contracted condition of FIG. 2;

FlG. 5 is a longitudinal section through a portion of a modified form of apparatus, with its seat structure in expanded condition; and

FIG. 6 is a view like FIG. 5, with the seat structure in contracted position.

The apparatus illustrated in the drawings is particularly adapted for use in the drilling of well bores underlying a body of water. Such well bores may either be drilled from a drilling platform resting on the ocean floor or from a drilling barge floating in the water above the well site. For purposes of clarity conventional well equipment that may have already been installed in the well bore and at the ocean floor have been omitted from the drawings. In the present case, a housing 10 is provided which is lowered into appropriate supporting engagement with a companion housing (not shown) which will encompass it, the housing having a downwardly tapering shoulder 11 adapted to engage a companion shoulder in the housing surrounding it and being locked in set position by an external split lock ring 12. The housing 10 is disclosed as having a plurality of inherently contraetable split lock rings 13 disposed in grooves 14 in longitudinal spaced relation to each other, but such lock ring arrangement forms no part of the present invention, being shown since they will serve to lock certain equipment run in the well bore to the housing.

The housing 10 also contains an inherently expandable split seat ring 15, the inside diameter of which is initially substantially the same as or only slightly less than the minimum inside diameter through the housing itself. This split ring is disposed in a longitudinal space 16 formed between a lower housing section 17, which is threadedly secured to an upper housing section 18. As described hereinbelow, the split ring 15 is adapted to be contracted or constricted so that it projects laterally inwardly of the inner housing wall 19 and thereby provides a solid seat on which a casing hanger (not shown) can be supported with casing suspended therefrom.

The housing sections 17, 18 define an annular cylinder space 29 by virtue of the fact that the lower section has 'a cylindrical skirt 21 in spaced relation to a cylindrical wall 22 of the upper housing section, the cylindrical skirt terminating in an inwardly directed cylinder head 23 engaging the inner wall 22 of the upper section 18. The upper end 24 of the skirt forms a lower guide shoulder against which the lower surface 25 of the split seat ring bears and along which it is laterally slidable. An opposed upper guide shoulder 26 is formed on the upper section and along which the upper side 27 of the split seat ring is in slidable engagement.

As was stated above, the split seat ring 15 is initially in its expanded'position, as illustrated in FIGS. 1, 3, being disposed substantially entirely outwardly of the inner wall 19 of the housing. Encompassing the split seat ring is a constrictor ring 28 that extends downwardly initially within the upper portion of the annular cylinder space 29, and which has an inwardly directed upper flange 30 received within a circumferential external groove 31 in the split seat ring, the lower portion 32 of the split seat ring 15 projecting into an internal circumferential groove 33 in the constrictor ring. The upper side 34 of the external ring groove is inclined in an upward and outward direction and is engaged by a companion inclined surface 35 of the constrictor ring flange 30. Similarly, the lower side 36 of the internal constrictor ring groove 33 is inclined in an upward and outward direction, engaging a companion external cam surface 37 on the split seat ring. Above its upper cam surface 34, the split seat ring terminates in an upwardly facing shoulder 38 located at the lower end of a longitudinal cylindrical surface 39 of the split seat ring of smaller diameter than the external diameter of the shoulder 38.

For the purpose of contracting the seat ring 15, the constrictor ring 28 is shifted upwardly along the split seat ring. Such upward shifting occurs as a result of hydraulically moving an annular piston 40, in the annular cylinder space 29 and located below the constrictor ring 28, in an upward direction, this piston being separate from the constrictor ring, although in engagement with its lower end. Fluid under pressure from the drilling platform or drilling barge is conducted through a suitable line 41 into an operating port 42 in the housing, which is in communication with a longitudinal fluid pressure passage 43 that terminates in an inlet port 44 leading into the lower portion of the cylinder space 29. The fluid is prevented from leaking upwardly past the piston 40 by an external seal ring 45 on the piston slidably and sealingly engaging the inner wall 22 of the outer housing section, and by a seal ring 46 in the cylinder skirt slidably and sealingly engaging the inner surface of the piston. Leakage of fluid in a downward direction from the cylinder space is prevented by a seal ring 47 in the cylinder head 23 sealingly engaging the inner wall 22 of the upper housing section.

Initially, the split seat ring 15, which is inherently expandable, occupies the position disclosed in FIG. 1, in which the constrictor ring 28 and piston 40 are in their lower positions, and in which the minimum inside diameter through the split seat ring is only slightly less than, or no less than, the minimum inside diameter through the housing 10. The absence of restriction in the housing (the various lock rings 13 will automatically expand outwardly into their respective grooves 14 when objects bear against them) permits the driller to run the appropriate size drilling equipment, such as drill bits and hole openers, through the seat ring 15 of a much larger diameter than if the seat projected into the housing, to drill a well bore of a diameter that will accommodate the required diameter of casing to be subsequently lowered into the drilled hole. As an example, if the bore diameter of the housing is l6% inches and a landing seat is to be provided of an internal diameter of 15 5/16 inches, such a landing seat, if provided initially, would prevent the well bore to be drilled to the desired diameter to accept 13% -inch casings, unless the well bore diameter were enlarged by a subsequent underreaming operation, or the driller would be forced to run casing smaller than the l3%-inch diameter required. In the resent case, the initial inside diameter of the split seat ring 15 can, by way of example, be 16% inches in diameter, which allows the proper size bit to be run with a l6 /4-inch hole opener thereabove, which will provide a hole large enough to run the desired l3%-inch casing in the drilled hole.

When the driller is ready to run the casing, he causes fluid under pressure from the drilling platform or drilling barge to pass through the pressure line 41 into the operating port 42 and longitudinal passage 43, and through the inlet port 44 into the lower end of the cylinder, which drives the piston 40 upwardly, forcing the constrictor ring 28 upwardly and camming or constricting the seat ring 15 inwardly to the extent at which the upper constrictor ring flange 30 rides past the shoulder 38, at which time the inner surface of the flange is disposed behind the ring surface 39 above the shoulder 38, and the lower inner surface 51 of the constrictor ring 28 is disposed behind the external surface 52 of the ring below its external groove 31, The surfaces 39, 50 and 51, 52 are longitudinal and parallel to the housing axis and will preclude outward expansion of the split seat ring 15, the shoulder 38 preventing the constrictor ring 28 from moving downwardly. The upper extent of movement of the constrictor ring 28 under the action of the O the cylinder 29, without having any pulling action or effect on hydraulic piston is limited by engagement of its upper end 53 55 with housing 10. Thus, a solid landing shoulder 54, which may taper in a downward direction, is provided by the upper portion of the seat ring 15, the lower inner surface 55 of the ring' also being tapered or beveled in an upward direction to permit devices to be moved therethrough without hanging up on the ring.

After the ring 15 is constricted, the desired diameter casing is run in the well bore and the casing hanger will land and come to rest on the tapered landing surface or shoulder 54 of the seat ring, the lock ring 13 thereabove snapping over the 5 hanger body (not shown) to preclude its upward movement.

The casing that has been run in the well bore can now be ccmented in place. Circulating fluid may be pumped down the casing string followed by cement, the circulating fluid passing upwardly around the casing string and through bypass ports 60 the constrictor ring 28, which remains in its upper locking position.

In the form of the invention illustrated in FIGS. 5 and 6, essentially the same apparatus is illustrated as in the embodiment described specifically above. However, the split seat ring 15a is made in two parts; that is, an outer split ring 70 and an inner split ring 1, both of which are inherently expandable. The outer split ring 70 bears the same relation to the constrictor ring 28 as in the other form of the invention, and the minimum bore through the inner split ring 71 is the same as in the other form of the invention. The two rings 70, 71 are interlocked to one another by external teeth 72 on the inner ring meshing with internal teeth 73 of the outer ring, the teeth engaging each other at a slightly upwardly tapering angle so that downward force imposed on the inner ring 71 tends to maintain it locked to the outer ring 70, and upward force on the outer ring tends to maintain it locked to the inner ring. Downward force on the inner ring 71 is transmitted to the outer ring 70, and through the latter to the lower guide shoulder 24 at the upper end of the lower housing section 17.

In all respects, the composite inner and outer rings 70, 71 initially occupy an expanded or lateral outward position, as illustrated in FIG. 5. Fluid pressure imposed through the port 42 and longitudinal housing passage 43 will move the annular piston 40 and constrictor ring 28 upwardly to expand the composite inner and outer split rings 70, 71 in an inward direction. If desired, a check valve can be disposed in the inlet port 44, consisting of a valve seat 81 engaged by a ball 82 and urged thereagainst by a helical compression spring 83. Fluid under pressure shifts the ball 82 inwardly against the force of the compression spring 83, the fluid then passing into the cylinder space 29. Should the fluid under pressure attempt to leave the cylinder space, the check valve ball element 82 engages its seat 81 to prevent such reverse flow.

By making the seat ring 15a of two pieces, that is, of an inner split seat ring 71 and an outer split seat ring 70, the stresses in the rings are reduced, to permit standard material to be employed, since the force required to constrict each of the rings is less than the force required to constrict an integral ring, as illustrated in FIGS. 1 to 4.

We claim:

1. In hanger apparatus for suspending a casing string in a well bore: a housing having a passage through which the easing string can be run and lowered in the well bore, said housing having axially spaced upper and lower guide surfaces normal to the axis of said housing; a hanger seat in said housing between said surfaces and having upper and lower guide surfaces normal to the axis of said housing a slidably engaging said housing guide surfaces to confine said seat for nonaxial radial movement, said seat initially occupying an outer position substantially completely free from the housing passage; and means for shifting said hanger seat radially along said housing guide surfaces partially inwardly of said passage to provide a support for a hanger connected to the upper portion of the casing string; said hanger seat comprising a split ring structure including an outer ring and an inner ring coupled to said outer ring.

2. In hanger apparatus as defined in claim 1; wherein said hanger seat comprises an inherently expandable split ring structure.

3. In hanger apparatus as defined in claim 1; wherein said shifting means comprises cylinder and piston means, and means for conducting fluid under pressure into said cylinder and piston means to actuate the same.

lOlOSO 0003 4. ln hanger apparatus for suspending a casing string in a well bore: a housing having a passage through which the easing string can be run and lowered in the well bore, said housing having axially spaced upper and lower guide surfaces normal to the axis of said housing; a hangar seat in said housing between said surfaces and having upper and lower guide surfaces normal to the axis of said housing and slidably engaging said housing guide surfaces to confine said seat for nonaxial radial movement, said seat initially occupying an outer position substantially completely free from the housing passage; and means for shifting said hanger seat radially along said housing guide surfaces partially inwardly of said passage to provide a support for a hanger connected to the upper portion of the casing string; said shifting means including an actuator having axially spaced cam surfaces thereon axially separated from one another and engaging said seat and shiftable axially of said housing and seat to shift said seat laterally inwardly of said housing passage, one of said cam surfaces being disposed under the other of said cam surfaces.

5. ln hanger apparatus as defined in claim 4; wherein said hanger seat comprises a split ring structure; said cam surfaces engaging said split ring structure and shiftable axially of said housing and split ring structure to shift said split ring structure laterally inwardly of said housing passage.

6. ln hanger apparatus as defined in claim 4; wherein said shifting means further comprises a cylinder in said housing, a piston in said cylinder operatively associated with said actua' tor, and means for conducting fluid under pressure to said cylinder to shift said piston and actuator axially of said housing and seat and cause said actuator to shift said seat laterally inwardly of said housing passage.

7. ln hanger apparatus as defined in claim 4; said actuator and seat having surfaces substantially parallel to the housing axis which coengage upon axial shifting of said actuator to retain said seat inwardly of said housing passage.

8. ln hanger apparatus as defined in claim 4; wherein said hanger seat comprises a split ring structure; said cam surfaces engaging said split ring structure and shiftable axially of said housing and split ring structure to shift said split ring structure laterally inwardly of said housing passage; said actuator and split ring structure having surfaces substantially parallel to the housing axis which coengage upon axial shifting of said actuator to retain said split ring structure inwardly of said housing passage.

9. in hanger apparatus as defined in claim 4; wherein said hanger seat comprises a split ring structure; said cam surfaces engaging said split ring structure, a cylinder in said housing, a piston in said cylinder operatively associated with said actuator, and means for conducting fluid under pressure to said cylinder to shift said piston and actuator axially of said housing and split ring structure and cause said actuator to shift said split ring structure laterally inwardly of said housing passage.

10. In hanger apparatus as defined in claim 4; wherein said hanger seat comprises a split ring structure; said cam surfaces engaging said split ring structure, a cylinder in said housing, a piston in said cylinder operatively associated with said actuator, and means for conducting fluid under pressure to said cylinder to shift said piston and actuator axially of said housing and split ring structure and cause said actuator to shift said split ring structure laterally inwardly of said housing passage; said actuator and split ring structure having surfaces substantially parallel to the housing axis which coengage upon axial shift of said actuator to retain said split ring structure inwardly of said housing passage.

11. in hanger apparatus for suspending a casing string in a well bore: a housing having a passage through which the easing string can be run and lowered in the well bore, said housing having axially spaced upper and lower guide surfaces normal to the axis of said housing; a hanger seat in said housing between said surfaces and having upper and lower guide surfaces normal to the axis of said housing and slidably engaging said housing guide surfaces to confine said seat for nonaxial radial movement, said seat initially occupying an outer position substantially completely free from the housing passage;

said housing having an annular cylinder; an annular piston in said cylinder; an annular actuator in said housing operatively associated with said piston and hanger seat; and means for conducting fluid under pressure into said cylinder to shift said piston axially in said cylinder and said actuator axially of said seat to shift said seat radially along said housing guide surfaces partially inwardly of said passage to provide a support for a hanger connected to the upper portion of the casing string; said hanger seat comprising an inherently expandable split ring structure; said actuator encompassing said ring structure and having one or more cam surfaces thereon engaging said structure to constrict said split ring structure inwardly of said housing passage upon axial movement of said actuator along said split ring structure, said split ring structure inherently expanding to said outer position prior to axial movement of said actuator to constrict said split ring structure.

12 In hanger apparatus as defined in claim 11; said actuator and split ring structure having surfaces substantially parallel to the housing axis which coengage upon axial shifting of said actuator to retain said split ring structure inwardly of said housing passage.

13. In hanger apparatus for suspending a casing string in a well bore: a housing having a passage through which the easing string can be run and lowered in the well bore, said housing having axially spaced upper and lower guide surfaces normal to the axis of said housing; a hanger seat in said housing between said surfaces and having upper and lower guide surfaces normal to to the axis of said housing and slidably engaging said housing guide surfaces to confine said seat for nonaxial radial movement, said seat initially occupying an outer position substantially completely free from the housing passage; and means for shifting said hanger seat radially along said housing guide surfaces partially inwardly of said passage to provide a support for a hanger connected to the upper portion of the casing string; said shifting means including an actuator having axially spaced cam surfaces thereon axially separated from one another and engaging companion axially spaced cam surfaces on said seat axially separated from one another, said actuator being shiftable axially of said housing and seat to cause said actuator cam surfaces to slide along said seat cam surfaces and shift said seat radially inwardly of said housing passage, one of said actuator cam surfaces being disposed under another of said actuator cam surfaces.

14. In hanger apparatus as defined in claim 13; said actuator occupying a lower position with said seat in its outer position, said actuator being shiftable upwardly of said housing and seat to cause said actuator cam surfaces to slide upwardly along said seat cam surfaces and shift said seat radially inwardly of said housing passage.

15. In hanger apparatus as defined in claim 13; said actuator and seat having surfaces substantially parallel to the housing axis which coengage upon axial shifting of said actuator to retain said seat inwardly of said housing p sa c.

16. IN hanger apparatus as defined in claim 13; said actuator occupying a lower position with said seat in its outer position, said actuator being shiftable upwardly of said housing and seat to cause said actuator cam surfaces to slide upwardly along said seat cam surfaces and shift said seat radially inwardly of said housing passage; said actuator and seat having surfaces substantially parallel to the housing axis which coengage upon axial shifting of said actuator to retain said seat inwardly of said housing passage.

17. In hanger apparatus for suspending a casing string in a well bore: a housing having a passage through which the easing string can be run and lowered in the well bore, said housing having axially spaced upper and lower guide surfaces normal to the axis of said housing; a'hanger seat in said housing between said surfaces and having upper and lower guide surfaces normal to the axis of said housing and slidably engaging said housing guide surfaces to confine said seat for nonaxial radial movement, said seat initially occupying an outer position substantially completely free from the housing passage; said housing having an annular cylinder; an annular piston in said cylinder; an annular actuator in said housing opcratively associated with said piston and hanger seat; and means for conducting fluid under pressure into said cylinder to shift said piston axially in said cylinder and said actuator axially of said seat to shift said seat radially along said housing guide surfaces partially inwardly of said passage to provide a Support for a hanger connected to the upper portion of the casing string; said hanger seat comprising an inherently expandable split ring structure; said actuator encompassing said ring structure and having axially spaced cam surfaces thereon engaging companion axially spaced cam surfaces on said ring structure, said actuator being shiftable axially of said housing and ring structure to cause said actuator cam surfaces to slide along said ring structure cam surfaces and constrict said split ring structure radially inwardly of said housing passage, said split ring structure inherently expanding to said outer position prior to axial movement of said actuator to constrict said split ring structure.

18. in hanger apparatus as defined in claim 17; said actuator occupying a lower position with said split ring structure in its outer position substantially free of said housing passage, said actuator being shiftable upwardly of said housing and ring structure to cause said actuator cam surfaces to slide upwardly along said ring structure cam surfaces and constrict said ring structure radially inwardly of said housing passage.

197 in hanger apparatus as defined in claim 17; said actuator and split ring structure having surfaces substantially parallel to the housing axis which coengage upon axial shifting of said aetuator to retain said split ring structure inwardly of said housing passage.

20. In hanger apparatus as defined in claim 17; said actuator occupying a lower position with said split ring structure in its outer position substantially free of said housing passage, said actuator being shiftable upwardly of said housing a ring structure to cause said actuator cam surfaces to slide upwardly along said ring structure cam surfaces and constrict said ring structure radially inwardly of said housing passage; said actuator and split ring structure having surfaces substantially parallel to the housing axis which coengage upon axial shifting of said actuator to retain said split ring structure inwardly of said housing passage.

July 13, 1971 Certificate of Correction Benton F. Baugh et a].

e-identified patent and that said Letters rt the attached sheets:

UNITED STATES PATENT OFFICE Patent No. 3,592,489

011 the cover sheet the illustrative drawing should appear as shown below:

0 w hb f e b mm mm we w w d 6 mm mn hm y e fir. fie h m t m a P Cancel the present sheet of drawing and inse Column 4, line 59, a should read and.

Column 5, line 64, shift should read sh1fting-. Column 8, line 13, a should read and.

Signed and sealed this 11th day of April 1972.

[SEAL] Attest ROBERT GoTrscHALK, Commissioner 0 f Patents.

EDWARD M. FLETCHER, JR., Attesting Oficer.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 S I -JL' Dated

Jul

3, 7

Inventor) Jonton k daugh, 01; a1.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column i line 59, "a" should read and Column 5, line 6L "shift" should read shifting Column 3, line 13, "a" should read and Cancel cover sheet and all sheets of drawings. Insert cover sheet and 2 sheets of drawings attached This certificate supersedes the Certificate of Jor-rection issued April ll, 1972.

Sign d and sealed this 30th da of April 1971;.

Attzst IJDUAFL'J 1-1.'l*L;l'IClIi .ii,J1' C. I-IARSHALL BALL! Attesting Ulficer 1 Commissioner of Patents M Poi-O50 10-59) USCOMM-DC 00576-P69

Claims

1. In hanger apparatus for suspending a casing string in a well bore: a housing having a passage through which the casing string can be run and lowered in the well bore, said housing having axially spaced upper and lower guide surfaces normal to the axis of said housing; a hanger seat in said housing between said surfaces and having upper and lower guide surfaces normal to the axis of said housing a slidably engaging said housing guide surfaces to confine said seat for nonaxial radial movement, said seat initially occupying an outer position substantially completely free from the housing passage; and means for shifting said hanger seat radially along said housing guide surfaces partially inwardly of said passage to provide a support for a hanger connected to the upper portion of the casing string; said hanger seat comprising a split ring structure including an outer ring and an inner ring coupled to said outer ring.

4. In hanger apparatus for suspending a casing string in a well bore: a housing having a passage through which the casing string can be run and lowered in the well bore, said housing having axially spaced upper and lower guide surfaces normal to the axis of said housing; a hangar seat in said housing between said surfaces and having upper and lower guide surfaces normal to the axis of said housing and slidably engaging said housing guide surfaces to confine said seat for nonaxial radial movement, said seat initially occupying an outer position substantially completely free from the housing passage; and means for shifting said hanger seat radially along said housing guide surfaces partially inwardly of said passage to provide a support for a hanger connected to the upper portion of the casing string; said shifting means including an actuator having axially spaced cam surfaces thereon axially separated from one another and engaging said seat and shiftable axially of said housing and seat to shift said seat laterally inwardly of said housing passage, one of said cam surfaces being disposed under the other of said cam surfaces.

5. In hanger apparatus as defined in claim 4; wherein said hanger seat comprises a split ring structure; said cam surfaces engaging said split ring structure and shiftable axially of said housing and split ring structure to shift said split ring structure laterally inwardly of said housing passage.

6. In hanger apparatus as defined in claim 4; wherein said shifting means further comprises a cylinder in said housing, a piston in said cylinder operatively associated with said actuator, and means for conducting fluid under pressure to said cylinder to shift said piston and actuator axially of said housing and seat and cause said actuator to shift said seat laterally inwardly of said housing passage.

7. In hanger apparatus as defined in claim 4; said actuator and seat having Surfaces substantially parallel to the housing axis which coengage upon axial shifting of said actuator to retain said seat inwardly of said housing passage.

8. In hanger apparatus as defined in claim 4; wherein said hanger seat comprises a split ring structure; said cam surfaces engaging said split ring structure and shiftable axially of said housing and split ring structure to shift said split ring structure laterally inwardly of said housing passage; said actuator and split ring structure having surfaces substantially parallel to the housing axis which coengage upon axial shifting of said actuator to retain said split ring structure inwardly of said housing passage.

11. In hanger apparatus for suspending a casing string in a well bore: a housing having a passage through which the casing string can be run and lowered in the well bore, said housing having axially spaced upper and lower guide surfaces normal to the axis of said housing; a hanger seat in said housing between said surfaces and having upper and lower guide surfaces normal to the axis of said housing and slidably engaging said housing guide surfaces to confine said seat for nonaxial radial movement, said seat initially occupying an outer position substantially completely free from the housing passage; said housing having an annular cylinder; an annular piston in said cylinder; an annular actuator in said housing operatively associated with said piston and hanger seat; and means for conducting fluid under pressure into said cylinder to shift said piston axially in said cylinder and said actuator axially of said seat to shift said seat radially along said housing guide surfaces partially inwardly of said passage to provide a support for a hanger connected to the upper portion of the casing string; said hanger seat comprising an inherently expandable split ring structure; said actuator encompassing said ring structure and having one or more cam surfaces thereon engaging said structure to constrict said split ring structure inwardly of said housing passage upon axial movement of said actuator along said split ring structure, said split ring structure inherently expanding to said outer position prior to axial movement of said actuator to constrict said split ring structure. 12 In hanger apparatus as defined in claim 11; said actuator and split ring structure having surfaces substantially parallel to the housing axis which coengage upon axial shifting of said actuator to retain said split ring structure inwardly of said housing passage.

13. In hanger apparatus for suspending a casing string in a well bore: a housing having a passage through which the casing string can be run and lowered in the well bore, said housing having axially spaced upper and lower guide surfaces normal to the axis oF said housing; a hanger seat in said housing between said surfaces and having upper and lower guide surfaces normal to to the axis of said housing and slidably engaging said housing guide surfaces to confine said seat for nonaxial radial movement, said seat initially occupying an outer position substantially completely free from the housing passage; and means for shifting said hanger seat radially along said housing guide surfaces partially inwardly of said passage to provide a support for a hanger connected to the upper portion of the casing string; said shifting means including an actuator having axially spaced cam surfaces thereon axially separated from one another and engaging companion axially spaced cam surfaces on said seat axially separated from one another, said actuator being shiftable axially of said housing and seat to cause said actuator cam surfaces to slide along said seat cam surfaces and shift said seat radially inwardly of said housing passage, one of said actuator cam surfaces being disposed under another of said actuator cam surfaces.

15. In hanger apparatus as defined in claim 13; said actuator and seat having surfaces substantially parallel to the housing axis which coengage upon axial shifting of said actuator to retain said seat inwardly of said housing passage.

17. In hanger apparatus for suspending a casing string in a well bore: a housing having a passage through which the casing string can be run and lowered in the well bore, said housing having axially spaced upper and lower guide surfaces normal to the axis of said housing; a hanger seat in said housing between said surfaces and having upper and lower guide surfaces normal to the axis of said housing and slidably engaging said housing guide surfaces to confine said seat for nonaxial radial movement, said seat initially occupying an outer position substantially completely free from the housing passage; said housing having an annular cylinder; an annular piston in said cylinder; an annular actuator in said housing operatively associated with said piston and hanger seat; and means for conducting fluid under pressure into said cylinder to shift said piston axially in said cylinder and said actuator axially of said seat to shift said seat radially along said housing guide surfaces partially inwardly of said passage to provide a support for a hanger connected to the upper portion of the casing string; said hanger seat comprising an inherently expandable split ring structure; said actuator encompassing said ring structure and having axially spaced cam surfaces thereon engaging companion axially spaced cam surfaces on said ring structure, said actuator being shiftable axially of said housing and ring structure to cause said actuator cam surfaces to slide along said ring structure cam surfaces and constrict said split ring structure radially inwardly of said housing passage, said split ring structure inherently expanding to said outer position prior to axial movement of said actuator to constrict said split ring structure.

19. In hanger apparatus as defined in claim 17; said actuator and split ring structure having surfaces substantially parallel to the housing axis which coengage upon axial shifting of said actuator to retain said split ring structure inwardly of said housing passage.