BACKGROUND OF THE INVENTION 1. Technical Field

[0001] Embodiments of the subject matter disclosed herein generally relate to subsea oil and gas pressure containment equipment. More particularly, the present technology relates to annular blowout preventors. 2. Discussion of the Background

[0002] A blowout preventer assembly is employed for offshore well drilling operations. The blowout preventer assembly includes a blowout preventer stack (BOP stack) that includes several ram preventers. The BOP stack lands on and connects to a wellhead housing either on the surface or on the sea floor. A surface BOP stack is configured with an annular BOP connected to several ram BOPs below with a connector on bottom that connects to a wellhead or high pressure housing. A subsea stack is configured with a lower marine riser package (LMRP) configured with one or two annular BOPs that connect to a tubular mandrel on the upper end of the lower BOP stack, which is configured with multiple ram BOPs with a connector on bottom for connecting to a subsea wellhead. The LMRP secures to a lower end of the riser and has control pods that control various functions of the BOP stack and LMRP. The LMRP also has one or more annular blowout preventers, which can seal around pipe of a variety of sizes as well as completely close the passage.

[0003] Both surface stacks and subsea stacks are large pieces of equipment, and are quite tall. It would be desirable to reduce the overall height and weight of the BOP assembly because of height restrictions when the equipment is stowed on the rig. A reduced height would allow the use of the equipment on rigs with a lower deck height and reduce the center of gravity and overall bending moment on a subsea wellhead. A reduced height and weight would allow for smaller rig designs or allow existing rigs to increase their operational limits. It would also allow for the installation of an additional ram BOP preventer in the BOP stack without adding the full height of the additional ram to the assembled BOP stack and LMRP. More generally, a reduced height annular BOP may be desirable for these and other reasons.

SUMMARY OF THE INVENTION

[0004] One embodiment of the present technology provides an annular blowout preventer (BOP). The annular BOP includes an annular housing having a base. The base includes a plurality of fasteners extending from an interior of the housing to an exterior of the housing via fastener holes formed through the connector base. The annular BOP further includes a seal plate positioned at least partially adjacent interior ends of the plurality of fastener. The annular BOP further includes an annular elastomeric element positioned within the interior of the housing and an annular piston positioned within the interior of the housing. The piston, when driven towards the elastomeric element, deforms the elastomeric element and forces the elastomeric element to constrict radially inward.

[0005] Another embodiment of the present technology provides subsea system which includes a riser coupled to a vessel, a lower marine riser package coupled to the riser opposite the vessel, and an annular blowout preventer (BOP) coupled to the lower marine riser package. The BOP includes an annular housing having a base. The base includes a plurality of fasteners extending from an interior of the housing to an exterior of the housing via fastener holes formed through the base. The annular BOP also includes a seal plate positioned at least partially adjacent interior ends of the plurality of fasteners, an annular elastomeric element positioned within the interior of the housing, and an annular piston positioned within the interior of the housing. The piston, when driven towards the elastomeric element, deforms the elastomeric element and forces the elastomeric element to constrict radially inward. The subsea system further includes one or more ram BOPs coupled to the annular BOP. [0006] Another embodiment of the present technology provides a method of installing an annular blowout preventer (BOP). The method includes placing a body of a housing of the annular BOP onto a ram BOP or subsea equipment, wherein the body has a base with a plurality of fastener holes formed therethrough. The method further includes securing the body to a ram BOP or the subsea equipment with a plurality of fasteners inserted through the plurality of fastener holes. The plurality of fastener holes is sealed off from the wellbore and hydraulic chamber to prevent leakage to the environment. The method further includes placing a top portion of the annular BOP onto the body. The top portion includes a cap, an elastomeric element, and a piston. The cap couples with the body to form the housing and enclose the elastomeric element and piston inside of the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present technology can be better understood on reading the following detailed description of nonlimiting embodiments thereof, and on examining the accompanying drawings, in which: [0008] FIG. l is a perspective view of a subsea BOP assembly.

[0009] FIG. 2 is a perspective view of a lower marine riser package.

[0010] FIG. 3 is a part exterior part cross-sectional view of an annular BOP according to an embodiment of the present disclosure.

[0011] FIG. 4 is a bottom view of a base of the annular BOP according to an embodiment of the present disclosure.

[0012] FIG. 5 is a detailed view of a connection between the annular BOP and either a ram BOP or another subsea equipment according to an embodiment of the present disclosure.

[0013] FIG. 6 is a partially exploded view of the annular BOP according to an embodiment of the present disclosure. [0014] FIG. 7 is a partially exploded view of an annular BOP, according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0015] The foregoing aspects, features, and advantages of the present technology can be further appreciated when considered with reference to the following description of preferred embodiments and accompanying drawings, wherein like reference numerals represent like elements. The following is directed to various exemplary embodiments of the disclosure. The embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, those having ordinary skill in the art can appreciate that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

[0016] Referring to FIG. 1, a prior art subsea riser assembly includes a blowout preventer (BOP) stack 11 that connects to a subsea wellhead housing (not shown) at the upper end of a well being drilled. The assembly also includes a lower marine riser package (LMRP) 13 that connects to the upper end of BOP stack 11. BOP stack 11 has a number of ram preventers 15 for selectively closing the passage through BOP stack 11. Some of the ram preventers 15 will close around a string of pipe (not shown) extending through BOP stack 11. At least one other ram preventer 15 will shear the string of pipe and close the passage.

[0017] FIGS. 1 and 2 are schematic illustrations, and LMRP 13 as shown in FIG. 2 appears slightly different; however, for the purposes concerned herein, they are equivalent. Referring also to FIG. 2, LMRP 13 is secured to a lower end of a riser 17 that extends up to a floating vessel or drilling platform at the sea surface. Riser 17 has a central main conduit through which strings of pipe are lowered into the well. Riser 17 also has auxiliary lines that connect to choke and kill lines 19 for circulating fluid to and from the BOP stack 11 below ram preventers 15. LMRP 13 has also control pods 21 supplied with hydraulic fluid pressure and/or electrical signals for controlling various components of LMRP 13 and BOP stack 11. LMRP 13 has one or more annular BOPs 23 (only one shown) that will close around pipe of a variety of sizes and also fully close in the event a pipe string is not extending through LMRP 13. A flex joint 25 connects an upper portion of LMRP 13 to riser 17. The lower of annular BOP 23 connects to a connector 27 which connects LMRP 13 to the upper end of BOP stack 11. In some embodiments, in the event of an emergency and for maintenance reasons, a signal may be sent to control pod 21 to cause connector 27 to disconnect from BOP stack 11. For a surface stack the annular is connected to the upper ram BOP.

[0018] FIG. 3 is a part exterior, part cross-sectional view of an annular BOP 29 according to an embodiment of the present disclosure. Annular BOP 29 has an annular housing 31 that is a generally tubular in shape. Annular housing 31 has a longitudinal axis 33 that passes concentrically through a central cavity 35. An annular piston 37 is axially movable in central cavity 35 in response to hydraulic fluid pressure applied to central cavity 35 above and/or below annular piston 37. An upper end portion of annular piston 37 engages an elastomeric element 41, which has a central passage through which a string of pipe (not shown) can be positioned. In some embodiments, upward movement of annular piston 37 deforms elastomeric element 41, causing the elastomeric element to constrict radially inward and thus constrict the central passage to seal around a string of pipe. If no pipe is present, the central passage will fully close.

[0019] In some embodiments, the annular housing 31 is comprised of a body 43 and a cap 45, in which the body 43 forms a bottom portion of the annular housing 31 and the cap 45 forms a top portion of the annular housing 31. The body 43 and the cap 45 are secured to each other to form the annular housing 31 and contain the piston 37 and the elastomeric element 41. In some embodiments, the cap 45 secures to the body 43 with a locking member 47. Cap 45 has a concentric upper opening 49 with a diameter the same or smaller than the diameter of central passage of the elastomeric element 41 when the elastomeric element 41 is not being deformed. A concentric lower opening 51 is located at a lower end of the body 43 and is the same or smaller diameter as upper opening 49.

[0020] The body 43 includes a connector base 39 located at the bottom of the annular BOP 29 and configured to connect the annular BOP 29 to another piece of equipment, such as a ram BOP or connector 27 (FIG. 2). A detailed view of a connection region 50 of the annular BOP 29 is shown in FIG. 4. FIG. 5 is a bottom view of the connector base 39. Referring to FIGS. 3 and 4, the connector base 39 has a plurality of fastener holes 53 formed therethrough. Specifically, the fastener holes extend from an interior of the annular BOP 29 or housing 31 to an exterior of the annular BOP 29 or housing 31. The fastener holes 53 allow fasteners 55 (e.g., bolts, studs, screws, etc.) to be placed therein and secure the annular BOP 29 to another piece of equipment below the annular BOP 29. FIG. 4 is a detailed view of a connection region 50 of the annular BOP 29 according to an embodiment of the present disclosure. Referring to FIGS. 3 and 4, specifically, the fasteners 55 extend from inside the annular BOP 29 to outside the annular BOP 29 beneath the annular BOP 29 where the fasteners 55 secure to another piece of equipment. As illustrated, the other piece of equipment may be positioned directly adjacent (i.e., beneath) the base 39 of the annular BOP. The fasteners 55 extend through the base 39 and directed into the other piece of equipment 73 (FIG 7), securing the annular BOP 29 and the other piece of equipment. In some embodiments, stud nuts 65 (or the like) may be applied to the fasteners 55 to secure the fasteners 55.

[0021] Referring still to FIGS. 3 and 4, the annular BOP further includes a seal plate 57 positioned at least partially adjacent interior ends of the plurality of fasteners. The seal plate 57 is also circular and concentric with the rest of the annular BOP 29. In some embodiments, the seal plate 57 extends across the entire area above the plurality of fasteners. Additionally, a first seal 59 is positioned circumferentially around the seal plate 57 and seals between the seal plate 57 and an interior surface 61 of the housing 31. In some embodiments, a seal 69 is positioned at an inner diameter 63 of the seal plate 57 and seals between the seal plate 57 and a piston sleeve 64. In some embodiments, a seal 72 is positioned beneath the piston sleeve 64 and seals between the piston sleeve 64 and the base 39. In some embodiments, a combination of such seals may be used to seal the fastener holes 53 off from the rest of the annular BOP 29.

[0022] A recessed chamber 67 is formed adjacent the fastener holes 53 to accommodate the fasteners 55 and stud nuts 65, and allows for sealing the region from the rest of annular BOP 29. Specifically, the recessed chamber 67 is sealed by the seal plate 57 and the first and second seals

59, 69. In some embodiments, a vent port 71 is formed in the housing 31 and communicatively couples the recessed chamber 67 to outside of the housing annular BOP 29. This allows for any leaks in the recessed chamber 67 to be detected, such as from wellbore fluids that may have moved past the piston sleeve seal 72 and/or hydraulic closing chamber seals 59 and 69. FIG. 6 illustrates another embodiment of an annular BOP 29. As illustrated, in some embodiments, the seal plate 57 may be integrated with the piston sleeve 64. That is, the seal plate 57 and the piston sleeve 64 are formed as one body. [0023] FIG. 7 is a partially exploded view of the annular BOP 29 according to an embodiment of the present disclosure. Because the fasteners 55 extend from within the housing of the annular BOP 29, the fasteners 55 are accessed from inside the annular BOP 29. Thus, the connection to another equipment 73 is made before the entire annular BOP 29 is assembled. FIG. 6 shows the assembling of the annular BOP 29 when connecting to another equipment 73. The body 43 (i.e., base 39) of the annular BOP 29 is first placed onto another equipment 73 and secured to the other equipment 73 via the fasteners 55, which traverse the base 39 of the annular BOP 29 and extends into the other equipment 73. In some embodiments, stud nuts (or the like) are secured to the ends of the fasteners 55 at the annular BOP side. Thus, the body 43 of the BOP 29 is securely coupled to the other equipment 73. The rest of the annular BOP 29 can then be assembled. In some embodiments, the piston 37, the elastomeric element 41, and the cap 45 may then be lowered/placed onto the body 43. The cap 45 locks into place with the body 43 to form the housing and contain the piston 37 and elastomeric element 41 therein. The entire annular BOP 29 is thereby connected to the other equipment 73. The other equipment may be any suitable piece of equipment that may be connected to an annular BOP, such as but not limited to a connector, or a spacer spool.

[0024] The annular BOP 29 of the present disclosure provides a way to create a connect between the annular BOP 29 and a ram BOP or a connector on a subsea stack to connect to the BOP stack 11 without the need for a connection flange, which is how the connection is conventionally made. The connection flange adds additional height and weight to the annular BOP 29. Thus, the present annular BOP 29 which is connectable directly from the base of the housing does not require the flange and thus can be shorter overall. [0025] While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, can appreciate that other embodiments may be devised which do not depart from the scope of the disclosure as described herein. Accordingly, the scope of the disclosure should be limited only by the attached claims.