Patent Application
20190178047
Embodiments of the present disclosure relate generally to annular blowout preventers, and more specifically, to an improved packing element for an annular blowout preventer.
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 and/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.
Blowout preventers are used extensively throughout the oil and gas industry. Typical blowout preventers include a main body to which are attached various types of ram units or packing units. The two categories of blowout preventers that are most prevalent are ram blowout preventers and annular blowout preventers. Blowout preventer stacks frequently utilize both types, typically with at least one annular blowout preventer stacked above several ram blowout preventers. A blowout preventer stack may be secured to a wellhead and may provide a means for sealing the well in the event of a system failure.
Annular blowout preventers generally include annular packing units or packing elements made at least partially from elastomeric material. Upon activation of the annular BOP, the packing element seals the wellbore. The annular blowout preventer typically includes a piston that is actuated (e.g., through pressurized air or fluid) into engagement with the elastomeric packing element. Such activation of the annular packing element compresses the elastomeric material within the annular space until the elastomeric material deforms in a radially inward direction to ultimately seal the wellbore. Metallic or other hardened segments are sometimes included in the annular packing element to help close off the wellbore and guide the elastomer.
Existing annular packing elements can have issues with rubber loss and decreased sealing performance when used over long periods of time. It is now recognized that an annular blowout preventer packing unit with improved sealing function and reduced elastomer loss over time is desired.
In accordance with an embodiment of the present disclosure, an annular blowout preventer (BOP) packing element having a bore formed therethrough includes an elastomer, an array of hardened segments, and an energizer/extrusion ring. The hardened segments are arranged circumferentially about a longitudinal axis of the packing element and bonded to an upper surface of the elastomer. The energizer/extrusion ring is bonded to a lower portion of the elastomer opposite the upper surface of the elastomer.
In accordance with another embodiment of the present disclosure, a method includes locking and sealing a tubular within an annular blowout preventer (BOP) via a packing element of the annular BOP. The packing element includes an elastomer, an array of hardened segments, and an energizer/extrusion ring. The hardened segments are arranged circumferentially about a longitudinal axis of the packing element and bonded to an upper surface of the elastomer. The energizer/extrusion ring is bonded to a lower portion of the elastomer opposite the upper surface of the elastomer.
For a more complete understanding of the present disclosure and its features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:
One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are 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.
Generally, embodiments of the disclosure are directed to an improved packing element that may be utilized in annular blowout preventers. Existing spherical packing elements function such that the elastomer (e.g., rubber) section is compressed and forced radially inward first and the metallic segments close around the tubular later. With this sequence of closing the packing element, there is a race between the elastomer and the metal segments as to which one is located first for sealing the wellbore. This leads to the possibility of parts of the rubber being extruded upward into a position between the tips of the metallic segments and the tubular, which can decrease the sealing function of the packing element.
The disclosed annular packing element overcomes the drawbacks associated with existing packing elements. Specifically, the disclosed packing element is arranged such that the timing of segment closure and rubber sealing is changed. The segment tips of the packing element close the extrusion gap first, and then the elastomer is squeezed in place for sealing.
The disclosed packing element may include an array of hardened metal segments, an elastomer, and an energizer/extrusion ring. The packing element may be a spherical annular packing element. The array of segments may be arranged radially about a longitudinal axis of the packing element and bonded to an upper surface of the elastomer. The energizer/extrusion ring may include an array of fingers projecting radially outward. The energizer/extrusion ring may be constructed from a hardened material and bonded to a lower surface of the elastomer opposite the upper surface of the elastomer. The energizer/extrusion ring may provide additional support to the packing element during actuation of the element into a closed configuration. Specific surfaces of the individual segments and the energizer/extrusion ring may be bonded directly to the elastomer in a manner that prevents the elastomer from extruding into the bore ahead of the segment tips closing. This may improve the sealing function of the packing element and prevent elastomer loss or degradation over long term use of the packing element.
Turning now to the drawings,
The annular BOP 10 generally includes a vertical bore 20 extending therethrough, and a tubular 22 may be disposed within the vertical bore 20. The tubular 22 may form part of a drillpipe, casing, riser, liner, production tubing, coiled tubing, or any other string of tubular that is being positioned within a wellbore below the BOP 10. The BOP 10 is designed to lock the tubular 22 in place and seal the tubular 22 against large pressures from downhole in the event of a kick or other unanticipated event.
The housing 14 may generally enclose the other components of the annular BOP 10. The housing 14 may be one continuous component or may include two or more outer housing components coupled together via appropriate fasteners such as bolts. An upper portion 24 of the housing 14 may have a curved or spherical shape for accommodating the annular packing element 12. Inside the housing 14, the annular packing element 12 is generally positioned above the piston 16, and the piston 16 is at least partially seated within the annular chamber 18.
One or more walls 26 located inside the housing 14 may define the annular chamber 18. As shown, for example, the annular BOP 10 may include a cylindrical wall 26 coupled to and extending upward from a bottom surface of the housing 14 to form a radially internal wall of the annular chamber 18. The rest of the annular chamber 18 may be defined by an external side wall of the housing 14 and the bottom surface of the housing 14, as shown. However, other arrangements of walls, surfaces, and similar components may define the annular fluid chamber 18 in other embodiments. Seals 28 are generally located between the walls of the chamber 18 and the piston 16 disposed therein.
Actuating the annular BOP 10 to close off and seal the tubular 22 generally involves directing pressurized fluid into the chamber 18. This pressurized fluid forces the piston 16 to move upward within the chamber 18. An upper surface 30 of the piston 16 presses directly into the annular packing element 12 in response to this upward movement. This force from the piston 16 compresses the packing element 12 against the surfaces of the housing 14, which direct the packing element 12 to collapse radially inward into locking/sealing engagement with the tubular 22 extending through the BOP 10.
As illustrated, the packing element 12 may be a spherical annular packing element having a rounded or spherical upper surface shape. The packing element 12 of
The energizer/extrusion ring 114 is located along a lower portion of the overall annular packing element 12, as shown in
The elastomer 112 generally forms a bulk portion of the packing element 12. The elastomer 112 is a single piece of material coupled between the lower surfaces of each of the hardened segments 110 and an upper surface of the energizer/extrusion ring 114. As mentioned above, the elastomer 112 may in some instances be formed entirely around the energizer/extrusion ring 114. The elastomer 112 has a cross-sectional shape that varies at different circumferential positions. The hardened segments 110 may be bonded directly to an upper surface of the elastomer 112 at certain circumferential positions, while the upper surface of the elastomer 112 may be exposed and uncovered at other circumferential positions. The elastomer 112 may be formed into the specific shape for the packing element 12 via a molding process, which will be described in detail below. The elastomer 112 may be made from rubber or any other desirable elastomeric material that is sufficiently compressible for use in the disclosed packing/sealing operation.
Having generally described the components that form the disclosed packing element 12, a more detailed description of the relative shape, dimensions, and arrangement of these components will now be provided.
The packing element 12 includes an array of several segments 110 disposed circumferentially about a longitudinal axis 120 (see
Each of the segments 110 used in the packing element 12 may have a substantially identical shape. However, one or more of the segments 110 may be constructed with a tapped hole 122 formed therethrough. The tapped holes 122 on the upper side of the two segments 110 may be used for mounting lifting components (e.g., hooks or rings) that allow for lifting of the packing element in/out of the BOP. As shown in
The segment 110 may include a body portion 126 and an outer flange portion 128. The flange portion 128 curves in an upward direction from a base 130 to a tip 132. The base 130 of the flange portion 128 is located at the furthest radial position from the longitudinal axis of the packing element once assembled, and the tip 132 of the flange portion 128 is located at the closest radial position to the axis. The base 130 of the flange portion 128 is wider in a circumferential direction (width 134) than the tip 132 of the flange portion 128 (width 136). Both sides of the flange portion 128 slope inwardly from the larger width 134 of the base 130 to the smaller width 136 of the tip 132. The flange portion 128 of the segment 110 may have a substantially consistent thickness 138 throughout its entire curved shape.
The flange portion 128 may have a rounded shape that defines the overall spherical profile of the fully assembled packing element. When fully assembled into the packing element, the flange portions 128 of the plurality of segments 110 form the uppermost surfaces of the packing element that directly engage the spherical housing of the annular BOP. The segments 110 are designed to flex radially inward in response to this engagement with the housing so that the tips 132 of the segments 110 are brought into closing contact with the tubular in the BOP before the elastomer comes into sealing contact with the tubular. The tips 132 of the many segments 110, once assembled into the packing element, partially define the bore through the packing element of the BOP.
The body portion 126 of the segment 110 may be entirely aligned with the symmetrical segment plane 124 and may extend along a lower surface 140 of the flange portion 128 from a center point of the tip 132 to a center point of the base 130. The body portion 126 may have a substantially consistent width 142 for its entire surface area. Upon assembly of the segment 110 into the packing element, the body portion 126 generally extends into the elastomer, as opposed to the flange portion 128 which sits atop the elastomer.
In the assembled position, the body portion 126 may be shaped with a first edge 144 that extends in a radially outward and downward direction from the tip 132 of the flange portion 128, and a second edge 146 that extends in a radially inward and upward direction from the base 130 of the flange portion 128. As shown, the two edges 144 and 146 may meet at a point 148 corresponding generally to a midpoint of the spherical curve of the flange portion 128. However, this point 148 may be repositioned in a different location by adjusting the angles of these edges 144 and 146 extending from the tip 132 and the base 130, respectively. In other embodiments, the body portion 126 may feature a curved profile as opposed to the one formed of two relatively straight edges 144 and 146 in the figures.
Turning to
The extended fingers 214 may provide increased stiffness to the lower portion of the packing element, as well as to distribute upward force from the actuating piston to the packing element in a controlled manner. The number of fingers 214 extending from the main body 212 of the ring 114 may coincide with the number of segments 110 disposed in the packing element. Upon assembly of the packing element, as shown in
As shown in
Turning to
Along the bore 310, the elastomer 112 may have a profile defined by a plurality of crests 312 and troughs 314. The crests 312 may each be aligned with the body portion of one of the segments 110, while the troughs 314 may each be located in a circumferential position between two adjacent segments 110. The elastomer 112 may slope radially outward and downward from each of the crests 312 at angles defined by the two corresponding edges 144 and 146 of the segment 110.
The elastomer 112 may similarly slope radially outward and downward from each of the troughs 314. However, the angles and lengths of sloping edges 316 and 318 of the elastomer 112 from the trough 314 to an outer surface of the packing element 12 may be different from the sloping edges from the crest 312 to the outer surface. Specifically, the angles of the sloping edges 316 and 318 of the elastomer 112 may each be larger (as measured from the vertical axis 120) than the corresponding sloping surfaces of the elastomer 112 defined by edges 144 and 146. At a radially outer surface of the packing element 12, a height 320 of the elastomer 112 at a circumferential position corresponding to the crest 312 is smaller than a corresponding height 322 of the elastomer 112 at a circumferential position corresponding to the trough 314. However, other shapes of the elastomer may be possible in other embodiments.
As shown in
It should be noted that, as illustrated, the edges 144 and tips 132 of the segments 110 are located relatively close to the diameter of the overall bore formed through the packing element 12. For example, the point 148 at which the edges 144 and 146 of the body portion of the segment 110 meet is located a radial distance 414 from the bore of the packing element 12, and this distance 414 is equal to approximately one third of a radial distance 416 from the point 148 to a radially outer edge of the packing element 12. The tip 132 of the segment 110, as shown, actually defines an upper part of the bore through the packing element 12. Because the edges 144 and tips 132 of the segments 110 are located closer to the drift diameter of the packing element 12, the tips 132 are in better position to be quickly closed into engagement with a tubular disposed therethrough before the elastomer 112 below the tips 132 reach the tubular. Instead, the tips 132 will be brought into contact with the tubular first, and the elastomer 112 will then be compressed into sealing engagement with the tubular at locations bounded by the tips 132 at the upper end and by the ring 114 at the lower end of the packing element 12.
After the bonding is applied, the segments 110, ring 114, and spacers 510 are arranged in a mold cavity in the arrangement depicted in
The presence of the energizer/extrusion ring 114 and having the surfaces of the segments 110 and ring 114 bonded to the elastomer 112 provides extrusion resistance of the elastomer into the bore of the BOP. That is, upper and lower portions of the elastomer do not extrude into positions that are radially between the closed tips 132 and the sealed tubular or radially between the ring 114 (and below piston) and the tubular. This improves the sealing function of the packing element 12 as compared to existing annular packing elements, because more elastomer is available to seal the space between the closed segments tips 132 at the top and the ring 114 at the bottom of the packing element 12. In addition, this lack of undesired elastomer extrusion prevents loss of elastomer from the packing element 12 from long-term use.
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.
