US3915424A

US3915424A - Blowout preventer with variable inside diameter

Info

Publication number: US3915424A
Application number: US412676A
Authority: US
Inventors: Robert K Lerouax
Original assignee: Hydril LLC
Current assignee: Hydril LLC
Priority date: 1973-01-26
Filing date: 1973-11-05
Publication date: 1975-10-28
Anticipated expiration: 1992-10-28

Abstract

A variable inside diameter blowout preventer capable of sealing off a bore or around an object against high well pressures, and which may be either a ram-type preventer or an annular preventer, and wherein a plurality of anti-extrusion members are disposed for radial and circumferential movement, with the adjacent members overlapping each other, and wherein the anti-extrusion members are interlocked to move together to inhibit or prevent extrusion of a resilient sealing member therewith.

Description

United States Patent [1 1 LeRouax [4 1 Oct. 28, 1975 BLOWOUT PREVENTER WITH VARIABLE INSIDE DIAMETER [75] Inventor: Robert K. LeRouax, Houston, Tex.

[73] Assignee: Hydril Company, Houston, Tex.

[22] Filed: Nov. 5, 1973 21 Appl. No.: 412,676

Related US. Application Data [63] Continuation-in-part of Ser. No. 326,836, Jan. 26,

1973, abandoned.

[52] US. Cl 251/1; 277/127 [51] Int. Cl. E21B 33/06 [58] Field of Search 251/1; 277/73, 126, 127, 277/129, 181, 185,188, 235; 166/81, 82, 84, 86, 88

[56] References Cited UNITED STATES PATENTS 2,035,925 3/1936 Seamark 277/34 2,246,709 6/1941 2,368,928 2/1949 King 166/10 2,609,836 9/1952 Knox 277/73 2,780,294 2/1957 Loomis.. 166/203 2,846,178 8/1958 Minor 251/229 X 3,038,542 6/1962 Loomis.. 166/204 3,572,628 3/1971 Jones 251/1 Primary Examiner-Martin P. Schwadron Assistant ExaminerRichard Gerard Attorney, Agent, or Firm-Pravel & Wilson [57] ABSTRACT A variable inside diameter blowout preventer capable of sealing off a bore or around an object against high well pressures, and which may be either a ram-type preventer or an annular preventer, and wherein a plurality of anti-extrusion members are disposed for radial and circumferential movement, with the adjacent members overlapping each other, and wherein the anti-extrusion members are interlocked to move together to inhibit or prevent extrusion of a resilient sealing member therewith.

13 Claims, 9 Drawing Figures Sheet 1 of 4 3,915,424

U.S. Patent Oct. 28, 1975 m IIIMJI 5%: ax

US. Patent Oct.28 1 f4 3,915,424

Sheet 3 of 4 US. Patent Oct. 28, 19 75 US. Patent Oct. 28, 1975 Sheet 4 of4 3,915,424

BLOWOUT PREVENTER WITH VARIABLE INSIDE DIAMETER CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of U.S. patent application Ser. No. 326,836 filed Jan. 26, 1973 copending herewith, and now abandoned BACKGROUND OF THE INVENTION The field of this invention is blowout preventers for oil wells and the like.

Annular blowout preventers made by the Hydril Company, an example of which is shown on page 2742 of the Composite Catalog for 1970-71, have been in extensive commercial use for a number of years. Such blowout preventers provide a fully-open bore there through so that drill bits, reamers, casing hangers and other large diameter tools can freely pass therethrough, but when actuated to the closed position, the packing of each such preventer is forced inwardly to reduce its bore and automatically adjust its size and shape in sealing contact with whatever object happens to then be in the bore of the preventer, thereby closing off the annular space around such object to prevent a blowout of well pressure from below. If no tool is in the well, the bore of the preventer can be fully closed to prevent a blowout.

Although such Hydril blowout preventers are very satisfactory for relatively low well pressures in the range of from about 2,000 psi. to 5,000 p.s.i., it is generally desirable to use a ram type blowout preventer above such pressures, and above 10,000 p.s.i. well pressure, it has heretofore been considered essential to use a ram type blowout preventer ofa predetermined opening size because of the inability to satisfactorily prevent extrusion of the rubber of the preventers at such higher pressures.

SUMMARY OF THE INVENTION The present invention relates to blowout preventers wherein a resilient sealing member or members are provided for closing a well bore or sealing with a pipe or other object disposed in the bore and wherein antiextrusion means are mounted with the sealing member or members to prevent extrusion thereof over a relatively large variable range of bore diametersfor the preventer, and wherein the blowout preventers of this invention may be of the ram type or the annular type, and are yet capable of sealing off much higher well pressures than with the prior known annular blowout preventers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of the annular blowout preventer form of this invention, showing the preventer in the fully open position;

FIG. 2 is a view similar to FIG. 1, but showing the blowout preventer housing partially rotated relative to FIG. 1 and also showing the preventer in the closed position on a pipe disposed in the well bore;

FIG. 3 is a view taken on line 3-3 to illustrate in detail the upper anti-extrusion means used with the blowout preventer of this invention;

FIG. 4 is a view taken on line 4-4 of FIG. 2 to further illustrate the details of the upper anti-extrusion means of this invention when in the closed or sealing position with a pipe or other object in the well;

FIG. 5 is an isometric view of one of the antiextrusion members shown in FIGS. 3 and 4;

FIG. 6 is an isometric view of the anti-extrusion members in the smallest diameter position corresponding to that shown in FIGS. 2 and 4;

FIG. 7 is a vertical sectional view illustrating a portion of another form of the blowout preventer of this invention wherein the blowout preventer rams are utilized;

FIG. 8 is a view taken on line 8-8 and illustrating in part the construction of the ram-type blowout preventer of FIG. 7, utilizing the anti-extrusion means of this invention; and

FIG. 9 is an isometric view illustrating a semicylindrical anti-extrusion means used with the blowout preventer rams of the preventer shown in FIGS. 7 and 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, the letter B refers generally to the form of the blowout preventer of this invention shown in FIGS. l6. Briefly, the preventer B includes a housing H which has a central longitudinal bore 10 through which a pipe P or other object is adapted to extend in the known manner for well operations. The housing H is constructed so that it is positioned in a stack of blowout preventers or in a string of well casing or pipe in any suitable manner, as will be well understood by those skilled in the art. The blowout preventer B is of the annular type and it has an annular or cylindrical sealing member S formed of rubber or other suitable yieldable resilient material. An upper anti-extrusion means M is provided above the sealing member S having an annular dished out or concave inner surface 11, and the lower anti-extrusion means M is provided below the sealing means or member S. In the normal undistorted position of the sealing member S and the open or expanded position of the anti-extrusion means M and M (FIGS. 1 and 3) the bore provided by the surface 11 is at least as large as the bore 10 of the housing H so that the fully open bore is provided for the passage of the pipe P and other well tools therethrough. However, upon the application of hydraulic pressure or the like, as will be explained, the sealing member S and the anti-extrusion means M and M are urged radially inwardly so that the well bore is closed off by the sealing of the member S with the pipe P. The anti-extrusion means M, as will be more fully explained serves to prevent longitudinal extrusion of the sealing member S relative to the pipe P.

Considering the details of the blowout preventer B as shown in FIGS. l6, the housing H may take numerous forms, an example of which is shown in the drawings and which includes a lower housing section 12 having a housing recess 12a for receiving an annular piston 14, the sealing member S and the anti-extrusion means M and M, as will be further explained. The annular piston 14 is formed of rubber or similar material which is capable of being contracted under pressure and its external portion is exposed to pressure such as hydraulic fluid which is introduced into the recess 12a through a fluid line 12b. Pressure is relieved from the recess 12a through a fluid pressure line 15b which is formed in a housing section or cover 15. The cover 15 is preferably secured to the housing section 12 by one or more bolts a (FIG. I). It is to be noted that the view of the housing H in FIG. 1 is rotated partially with respect to the sectional view of FIG. 2 so that in FIG. 2 the connecting threaded studs 15c and 12c are illustrated and these are used for connecting the housing H in the stack of blowout preventers or in the well casing or pipe in the known manner. The bolts 15a would thus be offset circumferentially with respect to the studs 15c.

The upper anti-extrusion means M is identical to the lower anti-extrusion means M, except that they are upside down with respect to each other. Therefore, the details of the anti-extrusion means M will be hereinafter explained and the same parts will normally be identified with the same numerals and/or letters which are followed by a prime mark to distinguish them from those of the anti-extrusion means M.

Considering now the upper anti-extrusion means M, such means M includes a plurality of anti-extrusion members 35 which are formed so that when assembled together they form a cylinder or ring (FIGS. 4 and 6) and which are capable of moving circumferentially with respect to each other as they move also radially from the innermost position of FIG. 6 to an open or retracted position of FIGS. 1 and 3.

Referring now to FIG. 5 in particular, wherein one of the anti-extrusion members 35 is illustrated, it can be seen that each of such members 35 includes a first section 35a which has an upper surface 35b and a lower surface 35c. It is also provided with

sides

35d and 35e. An interlocking recess 3511 is also formed with respect to the upper surface 35b, as will be more fully explained.

The surface 35c is the lower surface in the upper antiextrusion member 35 and it is bonded or suitably secured to the rubber or other material of the sealing member S so that each of the members 35 moves radially in response to radial movement of the material of the sealing member S.

The anti-extrusion member 35 is formed with a second section 35f which is actually integral with the first section 35a in the preferred form of the invention and which generally forms a stair-stepped configuration therewith (FIG. 5). The upper section 35f has a lower surface 35g and an upper surface 35h. The lower surface 35g is adapted to rest upon and slide relative to the surface 35b of the adjacent anti-extrusion member 35.

Also, the upper section 35f of the anti-extrusion member 35 includes an interlocking lug or projection 35k which is adapted to interflt and interlock in the recess 35n on the adjacent anti-extrusion member 35 so as to permit circumferential movement of the adjacent members 35 while causing the members 35 to move as a unit radially as the inner diameter or bore of the antiextrusion means M varies from the open or retracted position of FIG. 3 to the closed or sealing position of FIGS. 4 and 6. The innermost surface 35m of the antiextrusion member 35 is a single surface which is arcuate in shape so that the plurality of the members 35 form an inner bore or opening defined by such surface 35m.

The anti-extrusion members 35 are assembled in an overlapping relationship as seen in FIGS. 3 4 and 6 so that the lower surfaces 35g overlap with the adjacent surfaces 35b. Also, the interlocking lugs 35k interfit with the interlocking recesses 35e of the adjacent members 35. Thus, the anti-extrusion members 35 function as a unit and maintain their ring shape even though the diameter varies'from that shown in FIG. 3 to a smaller diameter down to the smallest diameter shown in FIGS. 4 and 6. The overlap of surfaces 35g and 35b inhibits longitudinal extrusion of the sealing member S. Also, the overlap of the inner surface of each lug 35k with its corresponding surface in the recess 35n prevents radial extrusion of the ring 14 between adjacent members 35.

The lower anti-extrusion means M is made up of anti-extrusion members 35 which are identical to the anti-extrusion members 35 except that they are upside down with respect thereto so that the surfaces 35c are disposed upwardly and are bonded to the rubber or other material of the sealing member S in the same manner as heretofore described in connection with the surfaces 35c. The functioning and operation of the lower anti-extrusion means M is identical to that heretofore described with respect to the anti-extrusion means M.

In the operation or use of the blowout preventer B shown in FIGS. 1-6, the anti-extrusion means M and M are in the opened or retracted position of FIG. 3 wherein the anti-extrusion members are circumferentially spaced from each other and have an inner bore defined by the inner surface 35m which is at least as large as the bore 11 of the sealing member S and the bore 10 of the housing I-I. Thus, the anti-extrusion means M and M do not interfere with the passage of the pipe P or other well tools through the bore of the well pipe. The sealing member S is in its normal undistorted condition when it has the maximum open bore as shown in FIGS. 1 and 3 and likewise the annular piston 14 is in its normal undistorted position when the blowout preventer is in the retracted open position of FIGS. 1 and 3.

To contract the sealing member S for sealing engagement with the pipe P or other object in the well, or even upon its self in certain embodiments of the sealing member S, hydraulic pressure or other fluid is introduced into the recess 12a through the fluid inlet pipe 12b (FIG. 2) to cause the annular piston 14 to contract and force the sealing member S inwardly into sealing engagement with the external surface of the pipe P. Since the

anti-extrusion members

35 and 35 are bonded or otherwise secured to the material of the sealing member S, they move radially inwardly with the sealing member S and maintain substantially the same inner opening or bore as the sealing member S so that at all times they prevent longitudinal extrusion of the material of the sealing member S. The inner surfaces 35m of the upper anti-extrusion members 35 and corresponding surfaces 35m of the lower anti-extrusion members 35 engage the external surface of the pipe P when the sealing members S are in contact with such pipe P so as to prevent the extrusion longitudinally of the material of the sealing members S.

When it is desired to release the blowout preventer from its sealing position of FIG. 2, the fluid pressure is relieved through line 15b or through line 12b so that the annular piston 14 returns by its inherent resiliency to the original position of FIG. 1 and likewise each sealing member S returns to its normal undistorted position of FIG. 1, carrying with it the

members

35 and 35 so that they return to the open position of FIG. 3.

In FIGS. 7-9, a modified form of the invention is shown wherein a blowout preventer B-l of the ramtype incorporates therewith the anti-extrusion means heretofore described in connection with FIGS. l-6, but modified so as to be semi-cylindrical for fitting with each of the rams R of the blowout preventer B-l. In FIGS. 7-9, the upper anti-extrusion means is identified by the designation M-l for each of the rams R to distinguish from the upper anti-extrusion means M shown in FIGS. 16, and similarly the lower anti-extrusion means for each of the rams R is designated M'-] in FIGS. 7-9.

The blowout preventer B-l may have any suitable type of housing such as the housing I-I-l which is of conventional construction and which is formed with a lateral opening 50 for receiving each ram R. Upper and lower flanges 50b and 50c, having bolt openings 50d for attaching the housing I-I-l in a stack of blowout preventers or in well casing in the known manner are provided.

The housing I-I-l has attached thereto a conventional head or bonnet 52 having a recess 52a (one of which is shown in FIG. 7) and each of which is aligned with the lateral openings 50 in the housing H-l so as to form a continuation thereof. The rams R are received in their respective recesses 52a when they are in their retracted position. A piston rod 54 extends through a suitable seal 52b in the bonnet 52 for each of the rams R. Each piston rod 54 extends to and connects with a piston 56 of conventional construction which is disposed in a cylinder 57 having an end cap or closure 58 secured therewith in any known manner. For purposes of illustration, a fluid inlet line 58a is shown for introducing hydraulic fluid or other operating fluid into the cylinder 57 for moving the piston 56 inwardly towards the center of the bore 50a of the housing I-I-l. Another fluid line 520 is provided for introducing hydraulic fluid or other fluid into the cylinder 57 for moving the piston 56 outwardly (to the right as viewed in FIG. 1) to retract each ram R connected therewith. It will of course be understood that the power means or piston arrangement illustrated in FIG. 7 for the right-hand ram R is duplicated for the left-hand ram R and therefore the details of the left-hand piston and power means are not shown.

For ease of description, the details of only one of the rams R will be described hereinafter, but it will be understood that the two rams R are preferably made in the same manner. Thus, each ram R has a ram carrier 60 which is connected to the piston. rod 54, preferably in the conventional releasable manner, utilizing a button 54a fitting into a suitable slot in the ram carrier 60. In the preferred form of the invention, the ram carrier 60 is formed of steel or other relatively rigid material and is preferably semi-cylindrical in cross-sectional shape (FIG. 8). The ram carrier 60 is provided with an internal recessor surface 60a which is likewise substantially semi-cylindrical in cross-sectional shape and whicn is adapted to receive a seal element 61 preferably having an external convex surface 61a which substantially conforms with the internal surface or recess 60a-(FIG. 8). The seal member 61 is formed of rubber or other yieldable material and it has therewith side anti-extrusion plates 62 formed of steel or other metal which are adapted to engage the inside surface of an inwardly extending lip 50f on the housing H-1.

The seal member 61 is confined at its upper end bein FIG. 7 when the rams R are brought into the closed position of FIG. 7. The rams R also each have a lower ram contining and alignment plate 65 with an end surface 65a on each end of each of the plates 65 for similar contact with each other in the closed position of the rams R as seen in FIG. 7.

It is to be noted that the vertical or longitudinal area between the upper alignment plate 64 and the lower alignment plate 65, and inwardly of the seal member 61, forms a pocket or recess which is generally semicylindrical for receiving the parts of the ram R of this invention which are normally the primary replaceable parts. Such replaceable parts includes a resilient yieldable sealing element or member S-] which is semicylindrical in cross-sectional shape and which is formed of rubber or other similar yieldable material. The upper anti-extrusion means M-1 and the lower anti-extrusion means M-l form the other parts of the replaceable assembly of each ram R.

Only the details of the upper anti-extrusion means M-l are fully illustrated in the drawings, since the lower anti-extrusion means M'-] is identical thereto except that it is upside down compared to the upper antiextrusion means M-l. Thus, as best seen in FIGS. 8 and 9, the upper anti-extrusion means M-l includes a plurality of anti-extrusion members 35 which are identical to those heretofore described in connection with FIGS. 3-6 and these are arranged in a semi-cylindrical form as shown in FIG. 9, with modified members at the terminal ends of the anti-extrusion means M-l.

Since the members 35 of the anti-extrusion means M-l are identical to the members 35 of the antiextrusion means M, the parts thereof are identified with the same designations and it will be understood that they are interrelated and function in the same manner. The end sections 135 are essentially one-half sections of the members 35 and they function in the same manner as can be readily seen from an examination of FIG. 9. The anti-extrusion section 135 on the left-hand end as viewed in FIG. 9 is essentially the upper section corresponding to the upper section 35fof each member 35 and therefore is designated as 135f and it includes a projection or interlocking lug 135k which interfits with a recess 35e on the adjacent member 35. Only a small portion of the surface l35c corresponding to the surface 350 is provided in such segment 135 and that surface 1356 is bonded to the rubber or other material of the sealing member S-l.

The segment or section 135 on the right-hand end of the anti-extrusion means M-l as viewed in FIG. 9 is essentially the lower section of one of the segments 35 and is therefore identified as 135a and it has substantially the entire surface 135C therewith which is bonded to the rubber or other material of the sealing member S-l. Its recess l35e interfits with the adjacent interlocking lug 35k in the same manner as the other members 35 interfit and interlock.

In the operation or use of the form of the invention shown in FIGS. 7-9, the blowout preventer B is operated in the conventional manner by the application of hydraulic pressure or other fluid pressure to the pistons 56 to move them inwardly and outwardly radially with respect to the bore 50a. When the pistons 56 are moved inwardly, the rams R move towards each other until the surfaces 64a and 65a engage each other to stop further inward movement of such parts and thereafter continued movement of the pistons 56 force the carriers 60 to move inwardly to contract and inwardly distort the sealing members S-l aboust the pipe P.

The anti-extrusion means M-1 and M-1 with each of the sealing members 8-1 on each ram R move inwardly with the sealing member S-l as heretofore explained so that they also contact the pipe and extend inwardly beyond the inner diameter of the

ram plates

64 and 65 to thus provide a variable inner bore diameter for the rams R and to provide a metal barrier at the upper and lower ends of each seal member 8-1 for inhibiting or preventing longitudinal extrusion of such seal member S-l relative to the pipe P.

Upon a retraction of the pistons 56 outwardly, the rams R are moved outwardly and the seal members S-1 and their anti-extrusion means therewith move outwardly to return to the open or retracted position wherein the members 35 are circumferentially spaced from each other as shown in FIG. 8. It will be appreciated that the members 35 move circumferentially and radially as they move from the retracted position to the inner sealing position with the pipe P so that such members 35 assume a close relationship to each other and may even approach a solid semi-cylindrical configuration corresponding to that illustrated in FIGS. 4 and 6 of the drawings for the anti-extrusion means M.

Instead of the dished out or concave surface 11, the shape of the surface 11 or other portions of the sealing member S may be modified, or recesses or the like in the member S may be provided, the purpose of which is to compensate, or partially compensate, for the smaller volume of the space available for the rubber of the member S when it is in its sealing position (FIG. as compared to the volume of the space available for such member S in its retracted position (FIGS. 1 and 9).

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials as well as in the details of the illustrated construction may be made without departing from the spirit of the invention.

I claim: 1. A blowout preventer adapted to seal with a pipe or other object in a well bore or to close same in the absence of any object in the well bore, comprising:

a resilient sealing member having an inner surface adapted to engage a pipe or the like in a well bore;

means for urging said sealing member radially inwardly for effecting a seal with a pipe or the like in a well bore or with itself for closing a well bore;

first anti-extrusion means mounted with said sealing member and movable circumferentially and radially therewith in response to radial inward move ment of said sealing member to a position contacting the pipe or object in the well bore for preventing extrusion of the sealing member longitudinally when fluid pressure acts on said sealing member, said first anti-extrusion means including:

a plurality of radially disposed anti-extrusion members mounted for radial movement in response to such movement of said sealing member; and

the adjacent ones of said anti-extrusion members having overlapping surfaces, the extent of overlap of which increases as the anti-extrusion members move radially inward with said sealing member.

2. The blowout preventer set forth in claim 1, wherein:

said sealing member is substantially semi-cylindrical and is adapted to be mounted as a part of a blowout preventer ram.

3. The blowout preventer set forth in claim 1,

wherein:

said sealing member is annular.

4. The blowout preventer set forth in claim 1, including:

second anti-extrusion means mounted with said sealing member on the opposite side longitudinally of said sealing member from said first anti-extrusion means and movable radially with said sealing member in response to radial inward movement of said sealing member to a position contacting the pipe or object in the well bore for inhibiting extrusion of the sealing member longitudinally when fluid pressure acts on said sealing member from either longitudinal direction.

5. The structure set forth in claim 4, wherein said second anti-extrusion means includes:

the adjacent ones of said anti-extrusion members having overlapping surfaces, the extent of overlap of which increases as the anti-extrusion members move radially inwardly with said sealing member.

6. The structure set forth in claim 5, wherein:

each of said anti-extrusion members has a first portion thereof which is bonded to said sealing member.

7. The structure set forth in claim 6, wherein:

each of said anti-extrusion members has a second portion which provides with a surface on the adjacent anti-extrusion member said overlapping surfaces which are spaced from said sealing member.

8. The structure set forth in claim 5, wherein said second anti-extrusion means includes:

means for interlocking said second anti-extrusion members together for radial movement together while permitting relative circumferential movement thereof.

9. The structure set forth in claim 1, wherein:

10. The structure set forth in claim 9, wherein:

11. The structure set forth in claim 1, including:

means for interlocking said anti-extrusion members for radial movement together while permitting relative circumferential movement thereof.

12. The structure set forth in claim 1, wherein said first anti-extrusion means includes:

a plurality of radially disposed anti-extrusion members disposed in a ring and movable circumferentially relative to each other as they move radially together;

each of said members having a lower section and an upper section in a stair-stepped configuration, with the lower section bonded to said sealing member, and with said upper section disposed away from the sealing member and slidably engaged with the adjacent anti-extrusion member.

3 ,91 5 ,424 9 10 13. The structure set forth in claim 12, wherein each an interlocking lug formed with said upper section anti-extrusion member includes: and adapted to slidably interfit with the interlockan interlocking recess formed on the upper portion ing recess on the adjacent anti-extrusion member.

of said lower section; and

Claims

1. A blowout preventer adapted to seal with a pipe or other object in a well bore or to close same in the absence of any object in the well bore, comprising: a resilient sealing member having an inner surface adapted to engage a pipe or the like in a well bore; means for urging said sealing member radially inwardly for effecting a seal with a pipe or the like in a well bore or with itself for closing a well bore; first anti-extrusion means mounted with said sealing member and movable circumferentially and radially therewith in response to radial inward movement of said sealing member to a position contacting the pipe or object in the well bore for preventing extrusion of the sealing member longitudinally when fluid pressure acts on said sealing member, said first anti-extrusion means including: a plurality of radially disposed anti-extrusion members mounted for radial movement in response to such movement of said sealing member; and the adjacent ones of said anti-extrusion members having overlapping surfaces, the extent of overlap of which increases as the anti-extrusion members move radially inward with said sealing member.

2. The blowout preventer set forth in claim 1, wherein: said sealing member is substantially semi-cylindrical and is adapted to be mounted as a part of a blowout preventer ram.

3. The blowout preventer set forth in claim 1, wherein: said sealing member is annular.

4. The blowout preventer set forth in claim 1, including: second anti-extrusion means mounted with said sealing member on the opposite side longitudinally of said sealing member from said first anti-extrusion means and movable radially with said sealing member in response to radial inward movement of said sealing member to a position contacting the pipe or object in the well bore for inhibiting extrusion of the sealing member longitudinally when fluid pressure acts on said sealing member from either longitudinal direction.

5. The structure set forth in claim 4, wherein said second anti-extrusion means includes: a plurality of radially disposed anti-extrusion members mounted for radial movement in response to such movement of said sealing member; and the adjacent ones of said anti-extrusion members having overlapping surfaces, the extent of overlap of which increases as the anti-extrusion members move radially inwardly with said sealing member.

6. The structure set forth in claim 5, wherein: each of said anti-extrusion members has a first portion thereof which is bonded to said sealing member.

7. The structure set forth in claim 6, wherein: each of said anti-extrusion members has a second portion which provides with a surface on the adjacent anti-extrusion member said overlapping surfaces which are spaced from said sealing member.

8. The structure set forth in claim 5, wherein said second anti-extrusion means includes: means for interlocking said second anti-extrusion members together for radial movement together while permitting relative circumferential movement thereof.

9. The structure set forth in claim 1, wherein: each of said anti-extrusion members has a first portion thereof which is bonded to said sealing member.

10. The structure set forth in claim 9, wherein: each of said anti-extrusion members has a second portion which provides with a surface on the adjacent anti-extrusion member said overlapping surfaces which are spaced from said sealing member.

11. The structure set forth in claim 1, including: means for interlocking said anti-extrusion members for radial movement together whilE permitting relative circumferential movement thereof.

12. The structure set forth in claim 1, wherein said first anti-extrusion means includes: a plurality of radially disposed anti-extrusion members disposed in a ring and movable circumferentially relative to each other as they move radially together; each of said members having a lower section and an upper section in a stair-stepped configuration, with the lower section bonded to said sealing member, and with said upper section disposed away from the sealing member and slidably engaged with the adjacent anti-extrusion member.

13. The structure set forth in claim 12, wherein each anti-extrusion member includes: an interlocking recess formed on the upper portion of said lower section; and an interlocking lug formed with said upper section and adapted to slidably interfit with the interlocking recess on the adjacent anti-extrusion member.