US20200157908A1

US20200157908A1 - Sealing Using Elastomeric Material Having Extrusion Resistant Elements

Info

Publication number: US20200157908A1
Application number: US16/198,690
Authority: US
Inventors: Christopher Nault; Ray Zonoz
Original assignee: Cameron International Corp
Current assignee: Cameron International Corp
Priority date: 2018-11-21
Filing date: 2018-11-21
Publication date: 2020-05-21

Abstract

Improved sealing technology is used for any pressure containing equipment including BOP equipment applications. Examples of such BOP equipment include annular BOPs, fixed pipe ram BOPs, variable bore ram BOPs, and shear and seal ram BOPs. A plurality of extrusion resistant elements are distributed within an elastomer material used for seals and packers, and the elements are shaped and positioned to reduce or eliminate extrusion at extrusion gaps.

Description

TECHNICAL FIELD

The present disclosure relates to systems and methods for sealing and packing devices. More specifically, the present disclosure relates to devices such as seals, packers, and the like used in environments wherein an elastic sealing material of the device is subjected to extrusion forces. Even more specifically, the present disclosure related to wellbore sealing equipment such as blowout preventers having a plurality of dense elements configured to resist extrusion of the elastic sealing material.

BACKGROUND

This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In well drilling operations such as in the oil and gas industry, blowout preventers (BOPS) are an important safety “valve” for well pressure control. BOPs typically use elastomer packer elements for sealing around a pipe. The elastomer packer elements when sealing off a higher pressure from below are exposed to extrusion forces. Some BOP designs use metallic inserts above the elastomer that are arranged to slide around the pipe being sealed upon. However, even with these metallic inserts there may still be some inherent gaps where the elastomer is exposed to extrusion forces. For example, with variable bore packers, such as variable bore ram-type BOPs and annular type BOPs, a relatively wide range of bore or pipe sizes can be accommodated and the metallic inserts which slide relative to one another when closing around pipe can leave exposed gaps in certain areas for the elastomer seal material to extrude through under extreme operating conditions. Likewise, seals with embedded garter springs are intended to prevent elastomer seal material from extruding through fixed radial gaps, however they may not work with variable bore sealing applications since the spring might be prone to stretch and extrude along with the elastomer.

SUMMARY

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining or limiting the scope of the claimed subject matter as set forth in the claims.
According to some embodiments, a sealing assembly is described that is configured to form a seal around an outer circumferential cylindrical surface to separate a higher-pressure environment from a lower-pressure environment. The assembly includes: one or more elastomeric members made at least in part of an elastomeric material and configured to form the seal between the higher and lower pressure environments, the seal being formed by one or more inner circumferential sealing surfaces of the one or more elastomeric members being forced into contact with the circumferential cylindrical sealing surface; one or more rigid members disposed adjacent to the elastomeric member and closer to the lower-pressure environment than the elastomeric member and configured to reduce extrusion of the one or more elastomeric members towards the lower-pressure environment; and a plurality of extrusion resistant elements in contact with the one or more elastomeric members, the extrusion resistant elements configured to reduce extrusion of the one or more elastomeric members through the one or more extrusion gaps.
According to some embodiments, the one or more extrusion gaps are formed between the one or more rigid members and the cylindrical sealing surface, and the plurality of extrusion resistant elements are distributed circumferentially at or near the one or more circumferential sealing surfaces of the one or more elastomeric members. According to some other embodiments, the one or more extrusion gaps are formed between the one or more rigid members and an adjacent sealing surface.
According to some embodiments, the extrusion resistant elements are formed of a metallic material, although other materials can be used that are suitably more resistant to extrusion under anticipated conditions as the elastomeric material used for the one or more elastomeric members.
The extrusion resistant elements can be configured to enable movements relative to each other during deformation of the one or more elastomeric members when being forced into contact with the circumferential cylindrical sealing surface. The extrusion resistant elements can be spherical in shape.
According to some embodiments, the sealing assembly forms part of a blowout preventer for a wellbore to be used for exploration and/or production of hydrocarbons from a subterranean rock formation.
According to some embodiments, a method is described for manufacturing a sealing assembly configured to form a seal around an outer circumferential cylindrical surface to separate a higher-pressure environment from a lower-pressure environment. The method includes: forming by injection molding one or more elastomeric members by injecting elastomeric material into a mold, the elastomeric members being configured to form the seal between the higher and lower pressure environments, the seal being formed by one or more inner circumferential sealing surfaces of the one or more elastomeric members being forced into contact with the circumferential cylindrical sealing surface; positioning a plurality of extrusion resistant elements circumferentially at or near the one or more circumferential sealing surfaces of the one or more elastomeric members, the positioning occurring prior or during the injection molding; and curing the one or more elastomeric members while the extrusion resistant elements are contained therein such that the extrusion resistant elements reduce extrusion of the one or more elastomeric members when the sealing assembly is actuated during sealing. According to some embodiments, the positioning is carried out using a carrier made of a similar or identical material as the elastomeric material used for the one or more elastomeric members.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject disclosure is further described in the following detailed description, and the accompanying drawings and schematics of non-limiting embodiments of the subject disclosure. The features depicted in the figures are not necessarily shown to scale. Certain features of the embodiments may be shown exaggerated in scale or in somewhat schematic form, and some details of elements may not be shown in the interest of clarity and conciseness.

FIG. 1 is a diagram illustrating a drilling and/or producing wellsite where sealing using elastomeric material having extrusion resistant elements could be deployed, according to some embodiments;

FIG. 2 is view of a ram type blowout preventer using elastomeric material having extrusion resistant elements could be deployed, according to some embodiments;

FIG. 3 is a perspective view showing further detail of a variable bore ram packer having extrusion resistant elements, according to some embodiments;

FIG. 4 is a side view showing further detail of a variable bore ram packer having extrusion resistant elements, according to some embodiments;

FIG. 5 is a diagram showing further detail of a variable bore ram packer member having extrusion resistant elements, according to some embodiments;

FIGS. 6A and 6B are top and perspective views of anti-extrusion elements and element carriers, according to some embodiments;

FIG. 7 is a cross-section view of an annular BOP that using elastomeric material having extrusion resistant elements, according to some embodiments;

FIG. 8 is a perspective view showing further detail of an annular packer having extrusion resistant elements, according to some embodiments; and

FIGS. 9 and 10 are top and cross-sectional views showing further details of an annular packer having extrusion resistant elements, according to some embodiments.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will be described below. These described embodiments are only exemplary of the present disclosure. Additionally, in an effort to provide a concise description of these exemplary embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
The particulars shown herein are for purposes of illustrative discussion of the embodiments of the present disclosure only. In this regard, no attempt is made to show structural details of the present disclosure in more detail than is necessary for the fundamental understanding of the present disclosure, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present disclosure may be embodied in practice. Like reference numerals represent similar or identical parts throughout the several views of the drawings.
According to some embodiments, improved sealing technology is described that is intended for any pressure containing equipment including BOP equipment applications. Examples of BOP equipment that can make use of embodiments include annular BOPs, fixed pipe ram BOPs, variable bore ram BOPs, and shear and seal ram BOPs. When elastomer material used for seals and packers are exposed to high temperatures and pressure, it tends to behave more fluid-like and eventually may fail at locations of stress concentration by extruding through small gaps or unsupported areas. The small gaps or unsupported area inherently exist between two assembled components which the seal is meant to be retained by and seal against. Components such as Annular and Variable Bore Ram packers are designed to seal at various diameters, therefore extrusion gaps may be more pronounced depending on the diameter at which it intended to seal around.
According to some embodiments, the elastomer seal or packer is molded with pre-placed metallic or other dense material spheres or other shapes. The metallic or other dense anti-extrusion elements are embedded and bonded to the elastomer during or after vulcanization process. The embedded spheres or other shaped geometry are intended to limit or prevent extrusion when subject to the high pressure and high temperature thereby improving performance of the seal at higher pressures and temperatures.
FIG. 1 is a diagram illustrating a drilling and/or producing wellsite where sealing using elastomeric material having extrusion resistant elements could be deployed, according to some embodiments. In this example, an offshore drilling system is being used to drill a wellbore 11. The system includes an offshore vessel or platform 20 at the sea surface 12 and a subsea blowout preventer (BOP) stack assembly 100 mounted to a wellhead 30 at the sea floor 13. The platform 20 is equipped with a derrick 21 that supports a hoist (not shown). A tubular drilling riser 14 extends from the platform 20 to the BOP stack assembly 100. The riser 14 returns drilling fluid or mud to the platform 20 during drilling operations. One or more hydraulic conduit(s) 15 extend along the outside of the riser 14 from the platform 20 to the BOP stack assembly 100. The conduit(s) 15 supplies pressurized hydraulic fluid to the assembly 100. Casing 31 extends from the wellhead 30 into the subterranean wellbore 11.
Downhole operations, such as drilling, are carried out by a tubular string 16 (e.g., drillstring) that is supported by the derrick 21 and extends from the platform 20 through the riser 14, through the BOP stack assembly 100, and into the wellbore 11. In this example, a downhole tool 17 is shown connected to the lower end of the tubular string 16. In general, the downhole tool 17 may comprise any suitable downhole tool(s) for drilling, completing, evaluating, and/or producing the wellbore 11 including, without limitation, drill bits, packers, cementing tools, casing or tubing running tools, testing equipment and/or perforating guns. During downhole operations, the string 16, and hence the tool 17 coupled thereto, may move axially, radially, and/or rotationally relative to the riser 14 and the BOP stack assembly 100.
The BOP stack assembly 100 is mounted to the wellhead 30 and is designed and configured to control and seal the wellbore 11, thereby containing the hydrocarbon fluids (liquids and gases) therein. In this example, the BOP stack assembly 100 comprises a lower marine riser package (LMRP) 110 and a BOP or BOP stack 120. The LMRP 110 includes a riser flex joint 111, a riser adapter 112, one or more annular BOPs 113, and a pair of redundant control units or pods. A flow bore 115 extends through the LMRP 110 from the riser 14 at the upper end of the LMRP 110 to the connection at the lower end of the LMRP 110. The riser adapter 112 extends upward from the flex joint 111 and is coupled to the lower end of the riser 14. The flex joint 111 allows the riser adapter 112 and the riser 14 connected thereto to deflect angularly relative to the LMRP 110, while wellbore fluids flow from the wellbore 11 through the BOP stack assembly 100 into the riser 14. The annular BOPs 113 each include annular elastomeric sealing elements that are mechanically squeezed radially inward to seal on a tubular extending through the LMRP 110 (e.g., the string 16, casing, drillpipe, drill collar, etc.) or seal off the flow bore 115. Thus, the annular BOPs 113 have the ability to seal on a variety of pipe sizes and/or profiles, as well as perform a “Complete Shut-off” (CSO) to seal the flow bore 115 when no tubular is extending therethrough.
According to some embodiments, the BOP stack 120 comprises one or more of the annular BOPs 113 as previously described with pressure sensor(s) 115, choke/kill valves, and choke/kill lines. A main bore 125 extends through the BOP stack 120. In addition, the BOP stack 120 includes a plurality of axially stacked ram BOPs 121. Each ram BOP 121 includes a pair of opposed rams and a pair of actuators that actuate and drive the matching rams. In this embodiment, the BOP stack 120 includes four ram BOPs 121. An upper ram can include opposed blind shear rams or blades for severing the tubular string 16 and sealing off the wellbore 11 from the riser 14. The three lower ram BOPs 121 include the opposed pipe rams for engaging the string 16 and sealing the annulus around the tubular string 16. According to some embodiments, one or more of the ram BOPs 121 can be variable bore ram (VBR) type BOPs. In other embodiments, the BOP stack (e.g., the stack 120) may include a different number of rams, different types of rams, one or more annular BOPs, or combinations thereof.
FIG. 2 is view of a ram type blowout preventer using elastomeric material having extrusion resistant elements could be deployed, according to some embodiments. Ram type blowout preventer 200 can be one of more of the BOPs 121 shown in FIG. 1. Ram type blowout preventer 200 includes a body or housing 212 with a vertical bore 125 and laterally disposed ram guideways 216. Bonnet assemblies 218 are mounted to the body 212 with suitable securing means such as studs or bolts 220 and aligned with laterally disposed guideways 216. Each bonnet assembly 218 includes an actuation means 222, including a pistons 224 and connecting rods 226. Each connecting rod 226 is connected to a ram 228 which includes variable bore ram packers 230. Each variable bore ram packer 230 includes embedded anti-extrusion elements 240. According to some embodiments, elements 240 are spherically shaped, although other shapes can be used. Actuation means 222 allows ram 228 and variable bore ram packer 230 to be reciprocated within guideways 216 or “opening and closing the rams” as it is referred to in the industry.
FIG. 3 is a perspective view showing further detail of a variable bore ram packer having extrusion resistant elements, according to some embodiments. Variable bore ram packer 230 includes packer member 334 made from an elastomeric material with suitable rheological characteristics and packer insert metallic plates 336 molded into one unitary structure with packer insert plates 336 arranged around a central opening 338 to form an insert array that is sized to fit closely about a tubular member. Extrusion resistant elements 240 are shown embedded in packer member 334 close to the upper and lower corners of central opening 338. As described in further detail infra, elements 240 are positioned where potential extrusion gaps are located. In the case shown, extrusion gaps can be located where the packer insert plates 336 are not able to perfectly match a particular diameter tubing outer surface. Packer pins 342 are molded into variable bore ram packer 230 for connecting variable bore ram packer 230 to ram 228 (shown in FIG. 2). When rams 228 are closed around a tubular member disposed in bore 125 of ram type blowout preventer 200 (all shown in FIG. 2), packer members 334 seal around the tubular member (not shown) within bore 125. FIG. 4 is a side view showing further detail of a variable bore ram packer having extrusion resistant elements, according to some embodiments.
In general, to perform optimally a seal should maintain uniform pressure loading, minimize or eliminate stress concentrations where extrusion may occur, and minimize extrusion gaps. Minimizing extrusion gaps and reducing stress concentrations should allow a seal or packer to perform at higher pressures and temperatures for longer periods of time.
According to some embodiments, elements such as spherical elements 240, are positioned in locations where extrusion gaps might otherwise exist. The elements 240 thus form a barrier to the potential gap by restricting the elastomer seal or packer from extruding. The spherical elements 240 may be a uniform diameter or of varying sizes. The elements 240 can act independently, be aligned in a single row, or arranged into another form such as a packed Body Center Cubic (BCC) arrangement. Depending on application, the spherical elements 240 may either retain their original spherical shape or deform. However, the spherical elements 240 are configured not to deform the extent they might be themselves extruded. According to some embodiments, the elements 240 are made of a relatively strong metallic material such as steel. According to some embodiments, other types of material may be used that has suitable mechanical properties under the anticipated pressure and temperature conditions. According to some embodiments, the material used for the anti-extrusion elements should be at least 2-3 times more resistant to extrusion than the elastomer material under the anticipated pressure and temperature conditions.
The embedded spherical elements 240 will support the pressure near the gap instead of the elastomer, thereby reducing the likelihood of the elastomer to extrude. The spherical elements 240, can be fully enveloped by the elastomer and will reduce stress concentrations in the elastomer by providing greater contact surface area. High internal elastomer pressure is shifted from the inherent gaps between the solid components to surface of the spheres. As shown, the elements 240 are positioned around the upper and lower inner edges of packer member 334. While potential extrusion gaps are not eliminated entirely, the elements 240 have been found to significantly reduce the likelihood for elastomers to fail by extrusion where gaps exist or when pressure and temperature combinations approach the normal operating limits of the equipment using existing methods and materials.
In variable bore sealing applications where components are required to translate/rotate relative to one another, the elastomer is configured to change its physical shape and extrusion gaps may be more irregularly shaped. Furthermore, in such applications the potential extrusion gaps have various sizes depending on the tubing diameter it is required to seal against. The spherical shapes in this instance have been found to move with the elastomer and be inserted to partially fill any voids or gaps created throughout the anticipated stroke of the equipment. In selecting suitable material, shape, and positioning for different applications, a goal should be to shift stress concentrations away from potential extrusion gaps and distribute the internal elastomer pressure to the larger surface area of the elements.
According to some embodiments, extrusion resistant elements can be positioned and configured to prevent extrusion at locations elsewhere within the sealing assembly. For example, extrusion gaps can potentially exist radially away from the central opening 338. Potential extrusion gaps might also be created in locations 350, near the back end of the packer insert plates 336, since the BOP separates pressure beginning from the outer surface of the tubular string 16 (shown in FIG. 1) radially outward to at least the inner diameter of the main drill through diameter of main bore 125 (shown in FIGS. 1 and 2). In general, potential extrusion gaps can exist across the entire diameter of main bore 125. Note that in cases where there is no tubular string present, i.e. closing and sealing on an open hole, then the BOP creates a seal on itself. In FIG. 4, a plurality of extrusion resistant elements 450 are positioned circumferentially to prevent extrusion of packer member 334 through gaps in location 350 (shown in FIG. 3). In general, extrusion resistant elements can be shaped and positioned strategically in any areas where extrusion may occur. Such element positioning and distribution can be linear, radial, or to follow a specific contour of the potential extrusion gap. According to some other embodiments, extrusion resistant elements could also be distributed randomly to achieve a desired ratio of extrusion resistant elements to elastomeric volume.
FIG. 5 is a diagram showing further detail of a variable bore ram packer member having extrusion resistant elements, according to some embodiments. In this more detailed view, the spherical shapes of the elements 240 is visible. According to some embodiments, the elements 240 are positioned using element carriers 510. Carriers 510 are shaped and positioned during the injection molding manufacturing process of packer member 334. While the carriers 510 are shown configured to hold two rows of elements 240, in some cases the carrier can simply be a circular elastomer tube loaded with an appropriate number of elements 240. It has been found that some types of carriers, such as carriers 510, allow for reducing movement and shifting of the elements during the injection molding process. The results are more accurate placement of the elements 240 within the packer member 334. According to some embodiments, the material used for carriers 510 can be the same or similar to the elastomeric material used for packer member 334. In such cases, during the curing process of packer member 334, the carriers 510 can become fully integrated with packer member 334. In some cases after curing the carriers 510 form an indistinguishable or nearly indistinguishable part of the packer member 334. FIGS. 6A and 6B are top and perspective views of anti-extrusion elements and element carriers, according to some embodiments.
According to some embodiments, the anti-extrusion elements should be positioned and configured to allow for some amount of shifting and/or sliding with respect to each other within the elastomer material while the elastomer is being deformed during sealing actuation. In the case shown in FIGS. 2-5, 6A and 6B, the elements 240 are arranged in two rows, or circles around the upper and lower inner edges of packer member 334. This is while the BOP is in the open position. When the BOP is closed around a tubing, the elements 240 should be allowed to shift around to some degree to allow for the elements being formed into a smaller diameter central opening. For example, when the packer is sealed against smaller tubing, the elements might end up being arranged in three or more rows in some locations instead of two rows in the open position. According to some embodiments, other densities of elements can be provided such as one row, or three or more rows of elements while in the open position. Additionally, while the elements 240 are shown arranged along both the upper and lower inner corners of the packer member 334, according to some embodiments, elements 240 might only be provided along the upper inner corner since that is where the material of packer member 334.
According to some embodiments, other techniques can be used in the manufacturing process other than using a carrier such as carriers 510. One alternative is interconnecting the elements with a string-like element(s). In one example a string element is passed through the center of each element to form a “necklace” type arrangement. The string can be made of a relatively flexible material to allow for the shifting and movement within the packer member during BOP actuation as described supra. According to other embodiments, the elements can be inserted in the packer member after the injection molding. For example, hole or openings could be formed in the packer member into which the elements are inserted. According to some embodiments, the elements could be bonded in place.
FIG. 7 is a cross-section view of an annular BOP that using elastomeric material having extrusion resistant elements, according to some embodiments. In this example, the BOP 113 can be one or both of the annular BOPs shown in FIG. 1. The BOP 113 includes elastomer packer 722. In order to close and seal the BOP 113, hydraulic fluid enters below piston 710 and pushes it upwards. The piston 710 lifts pusher plate 712, which in turn pushes on packer 722. The pressure forces the packer 722 radially inwards to form a seal with any tube within the BOP bore 125 (or sealing off the bore if there is no tube or pipe present). To re-open the BOP, the hyrdaulic fluid enters above the piston 710 thereby forcing it back downards. In some embodiments, separate pistons can be used for opening and closing the BOP 713. Metallic packer insert plates 736 are positioned above packer 722 and are configured to close around a tubular being sealed upon. Extrusion resistant elements 740 are shown embeded in packer 722. As in the case of elements 240 (shown in FIGS. 2-5, 6A and 6B), elements 740 are positioned where potential extrusion gaps are located. In the case shown, extrusion gaps can be located where the packer insert plates 736 are not able to perfectly match a particular diameter tubing outer surface.
FIG. 8 is a perspective view showing further detail of an annular packer having extrusion resistant elements, according to some embodiments. In particular the shape and configurations of packer insert plates 736 and extrusion resistant elements 740 are visible. FIGS. 9 and 10 are top and cross-sectional views showing further details of an annular packer having extrusion resistant elements, according to some embodiments. In the case of FIG. 10, the cross-section is along A-A′ shown in FIG. 9. According to some embodiments, the techniques described pertaining to manufacturing processes and other aspects of extrusion resistant elements 240 shown and described with respect to FIGS. 2-5, 6A and 6B, supra, can also be applied to elements 740.
While the disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the following appended claims.
The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for” or “step for” performing a function, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

Claims

What is claimed is:

1. A sealing assembly configured to form a seal around an outer circumferential cylindrical surface to separate a higher-pressure environment from a lower-pressure environment, the assembly comprising:

one or more elastomeric members made at least in part of an elastomeric material and configured to form the seal between the higher and lower pressure environments, the seal being formed by one or more inner circumferential sealing surfaces of the one or more elastomeric members being forced into contact with the circumferential cylindrical sealing surface;

one or more rigid members disposed adjacent to the elastomeric member and closer to the lower-pressure environment than the elastomeric member and configured to reduce extrusion of the one or more elastomeric members towards the lower-pressure environment; and

a plurality of extrusion resistant elements in contact with the one or more elastomeric members, the extrusion resistant elements configured to reduce extrusion of the one or more elastomeric members through one or more extrusion gaps.

2. An assembly according to claim 1 wherein said one or more extrusion gaps includes gaps formed between the one or more rigid members and the cylindrical sealing surface, and said plurality of extrusion resistant elements are distributed circumferentially at or near the one or more circumferential sealing surfaces of the one or more elastomeric members.

3. An assembly according to claim 2 wherein the plurality of extrusion resistant elements are configured to enable movements relative to each other during deformation of the one or more elastomeric members when being forced into contact with the circumferential cylindrical sealing surface.

4. An assembly according to claim 1 wherein said one or more extrusion gaps includes gaps formed between the one or more rigid members and an adjacent sealing surface.

5. An assembly according to claim 1 wherein said plurality of extrusion resistant elements are more than two times more resistant to extrusion than said elastomeric material under the anticipated pressure and temperature conditions.

6. An assembly according to claim 5 wherein said plurality of extrusion resistant elements are more than five times more resistant to extrusion than said elastomeric material under the anticipated pressure and temperature conditions.

7. An assembly according to claim 1 wherein said plurality of extrusion resistant elements are formed of a metallic material.

8. An assembly according to claim 1 wherein said plurality of extrusion resistant elements are spherical in shape.

9. An assembly according to claim 1 wherein said assembly forms part of a blowout preventer configured for use with a wellbore to be used for exploration and/or production of hydrocarbons from a subterranean rock formation.

10. An assembly according to claim 9 wherein the blowout preventer is an annular type blowout preventer.

11. An assembly according to claim 9 wherein the blowout preventer is a ram type blowout preventer.

12. An assembly according to claim 11 wherein the ram type blowout preventer includes variable bore rams and is configured to provide sealing around tubing sizes that range by at least 30 percent.

13. An assembly according to claim 11 wherein the ram type blowout preventer includes variable bore rams and is configured to provide sealing around a range of at least two tubing outer diameter sizes.

14. An assembly according to claim 1 wherein the plurality of extrusion resistant elements are positioned in an injection mold during manufacture of the one or more elastomeric members using a carrier made of a similar or identical material as the elastomeric material used for the one or more elastomeric members.

15. A method of manufacturing a sealing assembly configured to form a seal around an outer circumferential cylindrical surface to separate a higher-pressure environment from a lower-pressure environment, the method comprising:

forming by injection molding one or more elastomeric members by injecting elastomeric material into a mold, the elastomeric members being configured to form the seal between the higher and lower pressure environments, the seal being formed by one or more inner circumferential sealing surfaces of the one or more elastomeric members being forced into contact with the circumferential cylindrical sealing surface;

positioning a plurality of extrusion resistant elements circumferentially at or near the one or more circumferential sealing surfaces of the one or more elastomeric members, the positioning occurring prior or during said injection molding; and

curing the one or more elastomeric members while the extrusion resistant elements are contained therein such that the extrusion resistant elements reduce extrusion of the one or more elastomeric members when the sealing assembly is actuated during sealing.

16. The method of claim 15 wherein the positioning is carried out using a carrier made of a similar or identical material as the elastomeric material used for the one or more elastomeric members.

17. The method according to claim 15 wherein said assembly forms part of a blowout preventer, for a wellbore to be used for exploration and/or production of hydrocarbons from a subterranean rock formation.