BLOWOUT PREVENTER WITH PRESSURE-ISOLATED OPERATING PISTON ASSEMBLY
A ram-type blowout preventer including an operating piston assembly isolated from wellbore pressure effects is provided. In one embodiment, a blowout preventer includes piston coupled to a ram by a connecting rod, and the connecting rod is inserted into a recess in the ram. A pressure-isolating seal may be provided in the recess between the connecting rod and the ram to isolate the end of the connecting rod within the recess from wellbore pressure in the blowout preventer. Additional systems, devices, and methods are also disclosed.
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This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. 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 embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In order to meet consumer and industrial demand for natural resources, companies often invest significant amounts of time and money in finding and extracting oil, natural gas, and other subterranean resources from the earth. Particularly, once a desired subterranean resource such as oil or natural gas is discovered, drilling and production systems are often employed to access and extract the resource. These systems may be located onshore or offshore depending on the location of a desired resource. Further, such systems generally include a wellhead assembly through which the resource is extracted. These wellhead assemblies may include a wide variety of components, such as various casings, valves, fluid conduits, and the like, that control drilling or extraction operations.
More particularly, wellhead assemblies often include a blowout preventer, such as a ram-type blowout preventer that uses one or more pairs of opposing rams that press against one another to restrict flow of fluid through the blowout preventer. The rams typically include main bodies (or ram blocks) that receive sealing elements (or ram packers) that press together when a pair of opposing rams close against one another. Often, the rams are driven into and out of a main bore of a blowout preventer by operating pistons coupled to the rams by connecting rods. In a common design, a ram block includes a slot for receiving a button on the end of a connecting rod, which allows the operating piston and connecting rod to push and pull the ram block within the blowout preventer.
SUMMARYCertain aspects of some embodiments disclosed herein are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.
Embodiments of the present disclosure generally relate to systems having rams and operating piston assemblies in which the operating piston assemblies are isolated from certain pressure effects in the systems. More specifically, in some embodiments blowout preventers include operating piston assemblies with connecting rods coupled to rams and have seals between the connecting rods and the rams that isolate end faces of the connecting rods from wellbore pressure within the blowout preventer. This isolation may eliminate retraction forces that would otherwise be applied to the connecting rods by the wellbore pressure when the rams are closed at pressure, thereby decreasing forces transferred to wedge lock mechanisms that hold the rams in the closed position and increasing system efficiency. This isolation may also reduce the wellbore assist effect on the ram assemblies when closed at pressure, thereby increasing sealing fatigue life. In one embodiment, rather than being received laterally in a slot open to both an end face and a side of the ram, the connecting rod is threaded into a recess in the end face of the ram. Additionally, some embodiments also include relief paths that allow fluid within pressure-isolated regions in recesses of the rams to escape.
Various refinements of the features noted above may exist in relation to various aspects of the present embodiments. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. Again, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of some embodiments without limitation to the claimed subject matter.
These and other features, aspects, and advantages of certain embodiments will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these 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.
When introducing elements of various embodiments, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, any use of “top,” “bottom,” “above,” “below,” other directional terms, and variations of these terms is made for convenience, but does not require any particular orientation of the components.
Turning now to the drawings, a blowout preventer 10 is illustrated in
Bonnet assemblies 20 secured to the main body 12 include various components that facilitate control of sealing rams disposed in the blowout preventer 10, and locking assemblies 22 enable the sealing rams to be locked in a closed position. Particularly, as illustrated in the cross-sections of
In the embodiment depicted in
Again with reference to
In some embodiments, such as that of
The seal 52 may be formed of any suitable material, such as an elastomer. Once installed in the recess 42, the seal 52 seals against the bore of the recess 42 and isolates a region along an end face of the connecting rod 28 in the recess 42 from pressure on the other side of the seal 52 (e.g., pressure at the end face 40 of the ram 24). Such isolation reduces retraction force on the connecting rod 28 when the ram 24 is actuated into a sealing position. Particularly, when the rams 24 of the blowout preventer 10 are closed, wellbore pressure in the blowout preventer 10 (e.g., within the bore 14 below the rams 24 in
While this wellbore assist effect may help keep rams of a blowout preventer closed at pressure, left unchecked this same wellbore pressure would also apply a retraction force to the end face of a connecting rod in a ram, which in essence operates to try to push the connecting rod away from the bore of the blowout preventer and back into a bonnet assembly. If the operating pistons are not locked into place, a sufficiently large retraction force could cause the rams to open or leak. Also, in arrangements including a connecting rod having a button received in a slot of a ram, a sufficiently large retraction force could damage the button or the slot.
But unlike previous arrangements susceptible to this retraction force, present embodiments include a seal (such as seal 52) that isolates the operating piston assembly, and particularly the end face of the connecting rod in the ram, from wellbore pressure. This isolation reduces or eliminates the retraction force on the end face of the connecting rod from the wellbore pressure. The reduction of the retraction force on the connecting rod increases the closing ratio of the actuating piston and ram assembly, resulting in more efficient operation of the operating piston. And this increase in efficiency enables the system to be used at greater maximum pressures or to be reduced in size while handling the same maximum pressure as before. While the present pressure-isolated arrangement may be used in blowout preventers (or other sealing systems) of any rated pressure, this arrangement may find particular use in blowout preventers with higher pressure ratings, such as 20,000 psi, 25,000 psi, 30,000 psi, or even greater.
One ram 24 and its associated connecting rod 28 installed in the blowout preventer 10 are depicted in
As noted above, the inclusion of a pressure-isolating seal 52 between the connecting rod 28 and the ram 24 isolates the operating piston assembly from wellbore pressure effects, reducing or eliminating retracting pressure on the end face 70 (
But even with the pressure-isolating seal 52, it is possible in some instances that pressurized fluid may be present between the end face 70 and the bottom 48 of the recess 42. Consequently, in some embodiments the blowout preventer 10 includes a relief path (which may also be referred to as a vent path) leading away from the portion of the recess isolated by the seal 52 to allow fluid in the portion to escape from the recess 42. In the blowout preventer of
A blowout preventer 10 of another embodiment is depicted in the cross-sections provided in
While the aspects of the present 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. But it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.
Claims
1. A system comprising:
- a hollow body;
- a ram disposed in the hollow body; and
- a bonnet assembly coupled to the hollow body, the bonnet assembly including a piston and a connecting rod that connects the piston to the ram to enable the piston to drive the ram within the hollow body, wherein the connecting rod is coupled to the ram with a pressure-isolating seal.
2. The system of claim 1, comprising a locking assembly coupled to the bonnet assembly, the locking assembly including a wedge lock that enables the ram to be maintained in a closed position in the hollow body regardless of the level of hydraulic pressure on the piston.
3. The system of claim 2, wherein the connecting rod includes an end face received by the ram.
4. The system of claim 3, wherein the system comprises a blowout preventer including the hollow body, the ram, the piston and the connecting rod of the bonnet assembly, and the pressure-isolating seal.
5. The system of claim 4, wherein the pressure-isolating seal isolates the end face of the connecting rod received by the ram from wellbore pressure within the blowout preventer.
6. The system of claim 3, comprising a relief path enabling fluid to exit a pressure-isolated region between the end face of the connecting rod and the ram.
7. The system of claim 6, wherein the relief path extends from the pressure-isolated region through the connecting rod.
8. The system of claim 7, wherein the relief path extends from the pressure-isolated region to a slack chamber within the bonnet assembly.
9. The system of claim 6, wherein the relief path extends from the pressure-isolated region through the ram.
10. The system of claim 1, wherein the ram is a pipe ram configured to seal against a pipe in the hollow body.
11. A system comprising:
- a connecting rod; and
- a ram block including a recess formed in an end face of the ram block to enable receipt of the connecting rod within the recess;
- wherein the connecting rod and the ram block are constructed to allow the connecting rod to engage the recess by aligning the ram block with the longitudinal axis of the connecting rod and moving the connecting rod and the ram block together along the longitudinal axis such that the connecting rod enters the recess and into the ram block from the end face.
12. The system of claim 11, wherein the recess includes a threaded surface.
13. The system of claim 12, comprising a threaded retaining nut configured to be positioned about the connecting rod and to engage the threaded surface of the recess.
14. The system of claim 11, wherein the connecting rod and the ram block are assembled to one another such that the connecting rod is positioned within the recess of the ram block.
15. The system of claim 14, comprising a seal between the connecting rod and the ram block within the recess, wherein the seal isolates an end face of the connecting rod within the recess from pressure at the end face of the ram block.
16. The system of claim 15, wherein the seal is disposed about the connecting rod between a first retaining nut with an exterior threaded surface and a second retaining nut that is threaded onto the connecting rod via an interior threaded surface of the second retaining nut.
17. The system of claim 16, comprising a spacer also disposed about the connecting rod between the first retaining nut and the second retaining nut, wherein the spacer is positioned adjacent to the seal.
18. The system of claim 11, wherein at least one of the ram block or the connecting rod includes a relief path that enables fluid to escape from a portion of the recess that is between the seal and the bottom of the recess.
19. A method comprising:
- aligning a ram of a blowout preventer with a connecting rod; and
- coupling the ram to the connecting rod such that a pressure-isolating seal is positioned between the ram and the connecting rod.
20. The method of claim 19, wherein coupling the ram to the connecting rod includes threading the connecting rod into a recess in the ram.
Type: Application
Filed: Feb 2, 2015
Publication Date: May 28, 2015
Applicant: CAMERON INTERNATIONAL CORPORATION (Houston, TX)
Inventors: Johnny E. Jurena (Cypress, TX), David J. McWhorter (Pinehurst, TX), Charles E. Gibbs (Stafford, TX), Steven F. Shimonek (League City, TX)
Application Number: 14/611,815
International Classification: E21B 33/06 (20060101);