1. Field of Invention
The present disclosure relates in general to a variable ram packer for use with a blowout preventer (BOP) mounted on a wellhead. More specifically, the present disclosure relates to a variable ram packer with a packer element whose contact surface is reinforced.
2. Description of Prior Art
Wellbores in hydrocarbon bearing subterranean formations are formed by rotating a drill bit mounted on a lower end of a drill string. Typically, a wellhead housing is installed at the earth's surface and through which bit and string are inserted. A blow out preventer (BOP) stack usually mounts on top of the wellhead housing that provides pressure control of the wellbore, and often includes rams to shut in the wellbore should pressure in the wellbore become uncontrollable. Additional rams are often included with BOP stacks that are for shearing the string within the BOP stack, and also for pressure testing within the BOP. Further typically included with BOP stacks are flow lines and valves to allow fluid flow through the BOP stack for remediating overpressure in the wellbore.
One type of BOP ram for pressure testing within a BOP stack is a variable ram packer. Variable ram packers usually include a pair of hydraulically powered rams on opposing lateral sides of the BOP stack, which are selectively forced radially inward into compressive engagement with the tubular. An elastomer packer element is typically provided with the variable ram packers for engaging the tubular, and has a curved recess on its engaging surface for receiving the tubular. The curved recesses on the pair of packers form a seal in the bore and around the tubular so pressure in the wellbore can be verified. Adjacent the curved recess, each packer element often has a planar surface that defines an edge at the interface between the recess and planar surface. During operation of the variable ram packers, compressive stresses in the recess transfer to the unsupported edge portion and extrude it outward. Over time, the edge portion is susceptible to damage from these multiple extrusion cycles, especially during exposure to varying low and high temperatures.
Disclosed herein is an example of a variable ram, that in an embodiment includes a ram block selectively moveable within a blowout preventer (BOP) and a ram packer disposed in the ram block. In this example, the ram packer is made up of an elastomer body, a contact surface along a lateral side of the elastomer body, a recess portion on a mid-portion of the contact surface that projects radially into the elastomer body and that is in selective sealing engagement with a tubular in the BOP, and a reinforced area in the elastomer body adjacent the contact surface. Further in this example, the reinforced area has a stiffness greater than a stiffness of the elastomer body, so that when the ram block is moved radially inward into sealing contact with the tubular, the reinforced area exerts a restraining force on the elastomer body. The reinforced area can be made from a material such as neoprene, nitrile rubber, hydrogenated nitrile rubber, carboxylated nitrile rubber, or combinations thereof. In an embodiment, the contact surface adjacent an end of the recess portion is at an angle with respect to the recessed portion to define an edge on the contact surface, and wherein the reinforced area extends adjacent the edge. The elastomer body can be substantially solid, and the reinforced area can extend substantially along a length of the contact surface. In one example, the restraining force on the elastomer body retains the elastomer body in a non-extruded configuration when the ram block is moved radially inward into sealing contact with the tubular.
Also provided herein is a ram packer assembly for use in a blowout preventer (BOP), that in one example is made from an elastomeric body selectively disposed in a ram block. A contact surface is on the body, which has a curved recess that selectively seals against a tubular in the BOP. A reinforced area is integrally formed in the body adjacent the contact surface, so that when the body is forced against the tubular, the reinforced area exerts a force on that opposes extrusion of the body. A series of interlocking inserts may be included that selectively slide with respect to one another on a radial surface of the body when the body is radially compressed. The reinforced area can include neoprene, nitrile rubber, hydrogenated nitrile rubber, carboxylated nitrile rubber, or combinations thereof. The reinforced area can be provided along an interface between an end of the curved recess and an adjacent planar portion of the contact surface. In one optional embodiment, a portion of the body adjacent the reinforced area is stiffer than a portion of the body distal from the reinforced area.
A method is also disclosed that involves forming a ram packer assembly having a contact surface and that is for use in a blowout preventer (BOP). One embodiment of the method includes providing an uncured elastomer, disposing the uncured elastomer into a ram packer assembly mold, inserting the uncured elastomer into the mold, providing a substance for forming a reinforcing material, strategically disposing the substance for forming the reinforcing material in the mold to be adjacent the contact surface, and curing the uncured elastomer to form a body with the reinforced material integrally set in the body to define a reinforced area adjacent the contact surface that has a stiffness greater than a stiffness of the body. The method may further include providing sliding inserts in the mold that mount on opposing surfaces of the body. Optionally, the substance for forming a reinforcing material is a material from the group of neoprene, nitrile rubber, hydrogenated nitrile rubber, and combinations thereof. The body can be included into a ram packer assembly and sealed against a tubular, so that the reinforcing material restrains the body in an unextruded configuration.
Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:
While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims.
The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout.
It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation.
An example of a blowout preventer (BOP) 20 is shown in a side sectional view in
A perspective view of an example of packer assembly 14 is provided in
Further illustrated in the example of
In an embodiment, the reinforced area 38 includes one or more of neoprene, nitrile rubber, hydronated nitrile rubber, and carboxylated nitrile rubber. Tables 1 and 2 below include example values for properties of the reinforced area 38, or materials making up or included within the reinforced area 38. Examples exist wherein the materials having the properties of Tables 1 and 2 include one or more of hydronated nitrile rubber and carboxylated nitrile rubber.
One example of forming a packer element 16 is shown in
The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims.
This application claims priority to and the benefit of co-pending U.S. Provisional Application Ser. No. 61/747,589 filed on Dec. 31, 2012, the full disclosure of which is hereby incorporated by reference herein for all purposes.
Number | Date | Country | |
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61747589 | Dec 2012 | US |