The present invention relates to a wiper seal assembly for use in blowout preventers in the oil and gas industry.
Annular or spherical blowout preventers (BOPs) are large, hydraulically operated valves used in the oil and gas industry to control a wellbore at the ground level. Annular BOPs primarily function to seal or close the wellbore, when actuated, to thereby prevent a blowout.
Structurally, annular BOPs comprise a body formed by mating upper and lower housings that enclose a deformable, resilient sealing means for sealing the wellbore. The body further encloses a hydraulically operated piston, which actuates the opening and closing of the resilient means.
Contamination of the BOP hydraulic fluid system, by fluid and/or debris from the wellbore, needs to be prevented in order for the BOP to function properly. Various types of pressure seals are used to provide a physical separation between the fluids in the hydraulic fluid chamber and the wellbore. The prior art pressure seals conventionally used in this service, however, have not satisfactorily withstood the damage and degradation that occurs over time as a result of contaminants in the wellbore fluid. In addition, such common pressure seals are of a size and shape that they can roll or twist due to increasing pressure, thereby releasing their sealed engagement and allowing leakage of fluid. Accordingly, frequent inspection, repair and replacement of the common pressure seals is required in order to prevent the leakage of wellbore fluid into the hydraulic fluid system of the BOP.
One attempt to solve this problem has been to utilize what is known as a single, dual-functioning wiper seal, which serves to provide:
Dual-functioning seals, however, are not effective pressure seals and are still prone to degradation over time. Frequent repair and/or replacement of dual-functioning wiper seals continues to pose a problem for BOP manufacturers and operators in the oil and gas industry.
There is therefore a need for a wiper seal assembly that is designed to effectively seal the interface between the hydraulic fluid system of a BOP and the fluid within the wellbore, while at the same time resisting damage caused by wellbore fluid contaminants.
A hydraulically-operated annular blowout preventer, for controlling a wellbore, comprising a wiper seal assembly is described. The blowout preventer comprises:
The inner wall of the housing and the adapter ring each form an annular peripheral groove at the gap and each groove contains:
Various advantages and features of the present invention will become readily understood from the following detailed description taken in connection with the appended claims and the attached drawings, but omitting the main sealing means.
A wiper seal assembly will now be described with reference to
By way of background, a hydraulically operated blowout preventer (BOP), generally identified by 10, comprises a body 1, having an upper housing 2 and a lower housing 3 with a bore 4 extending therethrough. The bore 4 is an extension of, and communicates with, the wellbore of the well (not shown).
The lower housing 3 is annular and U-shaped, having a base wall 5 and inner and outer, radially spaced apart, upwardly projecting walls 6, 7. The walls 5, 6 and 7 cooperate to form an annular hydraulic fluid chamber 8. The inner wall 6 defines a section of the bore 4, which forms part of the wellbore.
An adapter ring 10 is connected with the upper end of the outer wall 7 and projects inwardly to partly close the upper end of the hydraulic fluid chamber 8. The upper end of the inner wall 6 and the adapter ring 10 define an annular gap 9 between them.
An annular piston 12 is slidably received by the chamber 8. The annular piston 12 comprises a vertically extending wall 13, an outwardly projecting lip 14 at the lower end of the piston wall 13 and an inwardly projecting lip 15 at the upper end of the wall 13. The outwardly projecting lip 14 is slidably positioned within the chamber 8, the vertically wall 13 extends through the gap 9, and the inwardly projecting lip 15 corresponds with the bore 4.
The vertical wall 13 of the piston 12 forms a first sealable interface 17 with the inner wall 6 of the lower housing 3, and a second sealable interface 19 with the adapter ring 10. First and second interfaces 17,19 seal the annular gap 9 and serve to isolate the fluid in the hydraulic fluid chamber 8 from the fluid and/or contaminants in the bore 4.
Having regard to
The wiper seal 22 may be extruded nitrile rubber having a durometer hardness of at least 70 (Shore A scale). In one preferred embodiment, the durometer hardness or the wiper seal 22 is between 85-95 Shore A. In a more preferred embodiment, the durometer hardness of the wiper seal is 95 Shore A.
The pressure seal 24 of the assembly provides a seal to prevent fluid and/or smaller contaminants that were not retained by the wiper seal 22 from leaking into the hydraulic fluid chamber 8. The pressure seal 24 may comprise a Polypak™ seal (Parker Seals, Utah, U.S.A.). In one embodiment, the pressure seal 24 may be a rectangular Polypak™ seal (Parker Seals, Utah, U.S.A.) thereby reducing the rolling or twisting of the seal within the groove 26.
Each wiper seal assembly 20 further comprises a retainer member 28, which is specifically configured to retain the wiper seal 22 and the pressure seal 24 in place in the groove 26. At the first interface 17, the retainer member 28 is formed by a lateral flange 30, that is integral to and projects outwardly from the inner wall 6, toward the inner surface of the piston's 12 vertical wall 13. At the second interface 19, a lateral flange 30 is integral to and projects inwardly from the adapter ring 10 toward the outer surface of the piston's 12 vertical wall 13.
In one embodiment, each retainer member 28 further comprises a downwardly depending lug 31 which projects from the lateral flange 30, thereby forming a “hook-shaped” configuration (see
In use then, the wiper seal 22 is retained in a “shielding” position at the first interface 17, by interference fit, between the retainer member 28 of the inner wall 6, the inner surface of the piston's 12 vertical wall 13 and the pressure seal 24. At the second interface 19, the wiper seal 22 is retained in position, by interference fit, between the retainer member 28 of the adapter ring 10, the outer surface of the piston's 12 vertical wall 13 and the pressure seal 24.
In conclusions, the interlocking of the wiper seal 22 and retainer member 28 configuration is used to effectively reduce both the axial and radial movement of the wiper seal 22 and to anchor the wiper seal 22 in a shielding relation to the pressure seal 24 within an annular BOP.
Although preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications to the wiper seal assembly defined herein might be made without departing from the scope of the invention. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
In the foregoing and in the examples, all temperatures are set forth uncorrected in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.
The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.