USRE38249E1 - Rotating blowout preventer and method - Google Patents

Abstract

The rotatable blowout preventer10comprises a stationary outer housing12and a rotatable inner housing38having a curved surface42thereon defining a portion of a sphere. An annular packer assembly46includes spherical packer elements for sliding engagement with the curved surface of the inner housing such that a packer assembly may seal against various sized tubulars. A lower rotary seal98between a piston56and the outer housing12is exposed to the differential between pressurized hydraulic fluid and the well pressure within a lower end of the bore32within the outer housing. A flow restriction member114between the rotatable inner housing and the outer housing reduces fluid pressure downstream from the flow restriction to less than 40% of the upstream pressure. The upper rotary seal120is open to atmospheric pressure and is subjected to this reduced pressure. Improved techniques are provided for passing hydraulic fluid through the blowout preventer for both closing and opening the sealing assembly46.

Description

FIELD OF THE INVENTION

The present invention relates to blowout preventers and, more particularly, relates to a rotating blowout preventer with spherical packing elements for use in hydrocarbon recovery operation. The blowout preventer of this invention is able to reliably withstand high pressure while maintaining sealed engagement with a tubular rotating at relatively high speeds, and also may be used to seal with a non-rotating tubular.

BACKGROUND OF THE INVENTION

Rotary blowout preventers for oil well drilling operations have existed for decades. U.S. Pat. No. 3,492,007 discloses a blowout preventer (BOP) for sealing well pressure about a rotating kelly or other production tool. U.S. Pat. No. 3,561,723 discloses a blowout preventer designed to prevent fluid from escaping from the well while the pipe string is either rotating or stationary. U.S. Pat. No. 4,098,341 discloses a rotating blowout preventer which is supplied with pressurized hydraulic fluid to lubricate and cool bearings within the BOP.

U.S. Pat. No. 4,378,849 discloses a blowout preventer with a mechanically operated relief valve to release high pressure surges in the annulus between the casing and the drill pipe sealed by the BOP packing. U.S. Pat. No. 4,383,577 discloses a rotating drilling head assembly which provides for the continuous forced circulation of oil to lubricate and cool thrust bearings within the assembly. A technique for fluidly connecting an outlet port of a BOP and an inlet of a choke manifold is disclosed in U.S. Pat. No. 4,618,314. The fluid may be injected into the blowout preventer for pressure testing and for charging the equipment with a desired fluid.

U.S. Pat. No. 5,178,215 discloses a rotary blowout preventer with a replaceable sleeve having a plurality of grippers therein. The blowout preventer disclosed in the '215 patent utilizes an inner packer which is responsive to hydraulic pressure to act against a sleeve which engages the drill pipe. The hydraulic fluid pressure which causes radial movement of the inner packer is sealed within the body of the BOP by seal assemblies which must withstand a pressure differential in excess of the difference between the well pressure and atmospheric pressure.

Improvements in rotating blowout preventers are required so that the blowout preventer may reliably withstand higher pressures, such as the high pressure commonly associated with underbalanced drilling. Underbalanced drilling occurs when the hydrostatic head of the drilling fluid is potentially lower than that of the formation being drilled. Underbalanced drilling frequently facilitates increased hydrocarbon production due to reduced formation damage, and results in both reduced loss of drilling fluids and reduced risk of differential sticking.

The disadvantages of the prior art are overcome by the present invention, and an improved blowout preventer and method of operating a blowout preventer are hereinafter disclosed. The blowout preventer is able to withstand high pressure while maintaining sealed engagement with a tubular rotating at relatively high speeds, and may also be used to seal with a non-rotating tubular.

SUMMARY OF THE INVENTION

The rotating blowout preventer of the present invention may be compatible with either kelly or top drive drilling systems. The spherical sealing assembly is capable of being used to strip tubulars and oilfield tubular connections, and will reliably seal with different diameter tubulars. The seal assembly may also maintain high pressure integrity when the tubular passing through the assembly is not rotating. Further, the spherical sealing assembly may seal off a well bore when no tubular is passing through the sealing assembly.

The rotating blowout preventer (RBOP) of the present invention is capable of reliable operation when the pressure differential between the well bore and atmosphere is in excess of 2000 psi and while the tubular is rotating at speeds of up to 200 rpm. The unit may also function as a non-rotating annular BOP with working pressure of up to 5000 psi. The assembly includes the ability for a complete shutoff of the empty bore at up to 2500 psi.

The spherical sealing element is actuated in response to axial movement of a fluid pressure piston. In order to minimize the diameter of the rotating seals, no rotating seals are provided on the outside diameter of the piston when applied fluid pressure causes sealing engagement of the spherical sealing elements. The piston closing force is generated by fluid pressure acting on the relatively large cross-sectional rod area of the piston between the lower seal and an upper adapter ting seal. The comparatively small cross-sectional flange area of the piston between the upper and lower adapter ring seals is used to open the RBOP. The piston and the adapter ring rotate together, and accordingly seals between these components are non-rotating.

The RBOP assembly includes a lower rotary seal between the stationary lower housing and the inner sleeve of the rotating piston. Closing pressure from the hydraulic supply to the RBOP is maintained at a selected value above the well bore pressure, so that this lower rotary seal is only exposed to a pressure differential of this selected value, e.g., from 200 psi to 500 psi. The upper rotary seal acts between the stationary upper housing and the rotating inner housing. A significant pressure drop is achieved across a restrictive flow bushing upstream of the upper rotary seal. The restrictive bushing floats radially with the rotating inner housing to accommodate eccentricity without generating excessive friction. The piston effect of the restrictive bushing prevents fluid flow between the bushing and the stationary upper housing and then above the bushing to the fluid outlet port. The hydraulic fluid thus passes between the outside diameter of the rotating inner housing and the inside diameter of the restrictive bushing to maintain a substantially uniform gap between the bushing and the inner housing. This substantially uniform gap may be maintained by a restrictive bushing radial bearing. The pressure of the hydraulic fluid drops significantly and at a substantially constant amount across the bushing, so that pressure acting on the upper rotary seal is continually only slightly greater than atmospheric pressure. Accordingly, the elastomeric upper rotary seal reliably isolates the low pressure hydraulic fluid from the environment.

The upper rotary seal and the lower rotary seal preferably have a diameter as small as practical, and also preferably have substantially the same diameter to balance the forces acting on the rotary components of the assembly. Pressurized fluid to the RBOP is provided in a closed loop system since fluid continuously flows past the restrictive flow bushing to maintain the desired low pressure drop across the upper rotary seal. The flow path of hydraulic fluid through the RBOP when the sealing elements engage the rotating tubular is past the lower rotary seal, then radially outward of the piston and the sealing assembly, past an inner housing thrust bearing, then past the restrictive flow bushing. The thrust bearing is spaced radially outward of and axially within the same plane as the restrictive flow bushing to reduce the axial height of the RBOP. The restrictive flow bushing preferably fits between cylindrical surfaces on the stationary upper housing and the rotary inner housing which each have an axis concentric with the central axis of the RBOP.

An opening chamber is formed between the upper and lower adapter ring seals and between the adapter ring and the piston. Although no outer rotating elastomeric seals are provided on the piston, the opening pressure to the RBOP is substantially restricted from passing beneath the piston by a metal-to-metal restriction between the adapter ring and an adapter ring bearing race. Since the sealing assembly is not rotating when the RBOP is opened, this metal-to-metal restriction need only be a static restriction.

It is an object of the present invention to provide an improved rotary blowout preventer which utilizes a spherical sealing assembly. A further object of the present invention to reduce to pressure applied to the upper rotary seal of an RBOP by providing a flow restrictive member upstream of the upper rotary seal, and continuously circulating fluid past the flow restrictive member.

It is a feature of the present invention that hydraulic fluid supplied to the RBOP for actuating the sealing assembly is first directed past the lower seal assembly, then in a path radially outward of both the actuating piston and the sealing assembly, then past an inner housing thrust bearing, and finally past a restrictive member which reduces the differential pressure applied to the upper seal assembly. It is a further feature of the present invention that the thrust member is radially outward of and in substantially the same horizontal plane as the flow restrictive member to reduce the height of the RBOP. A further feature of the invention is that the flow restrictive member resides between the cylindrical surfaces each having an axis substantially concentric with a central axis of the RBOP. Still another feature of the invention is the ability to reliably open the RBOP in response to fluid pressure applied to the RBOP and without providing a dynamic elastomeric seal on the outer diameter of the piston.

It is an advantage of the present invention that the rotating blowout preventer may also reliably seal under high pressure against a non-rotating tubular passing through the RBOP. The sealing assembly of the RBOP is able to reliably seal against different sized tubular members or against a non-tubular member passing through the RBOP. The sealing assembly further has the ability for a complete shutoff of the well with no tubular passing through the RBOP. The RBOP assembly is capable of being used to strip various tubulars and oilfield tubular connections. The assembly may be used with either kelly or top drive drilling systems.

These and further objects, features, and advantages of the present invention will become apparent in the following detailed description, wherein reference is made to the figures in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial view, partially in cross-section, of a rotating blowout preventer according to the present invention. The side right of the centerline is shown in the open position, and the side left of the centerline is shown in the closed position.

FIG. 2 is a detailed cross-sectional view illustrating one embodiment of a fluid restrictive member and an upper rotary sealing element as shown in FIG. 1 when the RBOP is in the closed position.

FIG. 3 is a detailed cross-sectional view illustrating the position of the adapter ring relative to the lower ball beating when the RBOP is in the open-position.

FIG. 4 is a detailed cross-sectional view illustrating an alternative embodiment of a fluid restrictive member and an upper rotary sealing element when the RBOP is in the closed position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts a rotating blowout preventer (RBOP)10 according to the present invention. The sealing assembly of the RBOP is open on the right side of the figure, while the left side of the same figure shows the sealing assembly in the closed position for engagement with an oilfield tubular. Those skilled in the art will appreciate that theRBOP10 of the present invention is functionally improved compared to most commercially available blowout preventers, in that the assembly is designed so that the sealing assembly discussed hereafter may remain in engagement while the tubular member is rotating within a wellbore.

Assembly10 comprises a stationaryouter housing12, which may be formed fromlower housing14 andupper housing16 each having mating flanges for secured engagement byconventional bolts18. A static O-ring19 provides sealed engagement between the stationarylower housing14 and theupper housing16. Opposing housing ends each include a respectiveplanar surface13 for sealed engagement with conventional oilfield equipment. The end of each housing is provided with agroove15 for receiving a conventional ring gasket for sealed engagement with such equipment. A plurality of circumferentially spaced threadedports17 are provided for receiving conventional securing members to connect such equipment to theassembly10. Accordingly, theassembly10 is compatible with various types of oilfield equipment.

Those skilled in the art will appreciate that hydraulic fluid may be applied to actuate theassembly10 as shown in FIG. 1 in a conventional manner. The pressurizedfluid source20, such as a pump, may be used to supply hydraulic fluid to theassembly10 from a hydraulic supply orreservoir22. Pressurized hydraulic fluid is supplied to theassembly10 throughlines24, which interconnect thepressurized source20 with afluid closing port26 in thelower housing14, afluid opening port28 in theupper housing16, and afluid output port27 in theupper housing16. As explained subsequently,port26 is the input port for hydraulic fluid when thevalve30 is positioned for closing the RBOP about a tubular member, andport27 is an output port for returning the hydraulic fluid to thereservoir22. Those skilled in the art will appreciate that the hydraulic system as shown in FIG. 1 may also include conventional filters and heat exchangers. Moreover, the fluid pressure supplied by thesource20 is preferably controlled in response to measured pressure in the wellbore. Accordingly, sensors, gauges, and a computer (not depicted) may be used for controlling the supply of hydraulic fluid to theassembly10.

Thestationary housing10 defines acylindrical bore32 through the RBOP, which determines the maximum size of the tubular which may be used for aparticular assembly10. The upper and lower innercylindrical walls34 and35 of thehousing12 thus determine the nominal diameter of the RBOP. Thehousing12 thus may define avertical centerline36 which is coaxial with the centerline of the tubular passing through the RBOP.

Theassembly10 also includes a rotatableinner housing38 which is rotatably guided by alarge thrust bearing40.Bearing40 has its upper race in engagement with thestationary housing12, and its lower race in engagement with the rotatableinner housing38. The upper race of thebearing40 is retained in place by an interference fit.Port41 in thehousing16 is provided for applying pressure to the upper race during disassembly for breaking the interference fit connection between the bearing40 and thehousing16. The cylindricalinner surface44 of the inner housing sleeve has a diameter equal to or slightly more than the diameter ofcylindrical surface34 on the stationary housing. The rotatable inner housing includes a curved surface42, which curved surface is formed by a portion of a sphere having a center on or substantially adjacent thecenterline36.

A sealingassembly46 is provided within rotatableinner housing38, and includes a plurality of circumferentially arrangedmetal elements48 and an annularelastomeric sealing element52.Pins49 keep theinner housing38 within theupper housing16 during assembly of the upper and lower housings, thereby retaining in place the bearings and seals between theinner housing38 and theupper housing16. Each of themetal elements48 has a curvedouter surface50 for sliding engagement with the similarly configured curved surface42 on the inner housing as explained hereafter. Annularelastomeric element52 provides for sealing engagement with the tubular, while the outer annularelastomeric element54 provides sealing engagement between themetal elements48 and the rotatableinner housing38.

It is a particular feature of the present invention that the RBOP be provided with a spherical sealing assembly, i.e., a sealing assembly adapted for sliding engagement with a spherical surface on the rotatable inner housing. Spherical sealing assemblies of the type generally shown in FIG. 1 have been reliably used for years in non-rotating blowout preventers, and have advantages over other types of sealing assemblies. Sealingassembly46 as shown in FIG. 1 may maintain high pressure sealing integrity with various diameter tubulars passing through the assembly, and may also seal with non-cylindrical members.Assembly10 according to the present invention is thus compatible with either kelly or top drive drilling systems, and is capable of being used to strip various tubulars and oilfield tubular connections. Spherical sealingassembly46 also has the ability for complete shutoff of the well with no tubular passing through the RBOP.

Theassembly10 includes an axiallymovable piston56 which comprises a radially outward sleeve-shapedring member57, a radially inner sleeve-shapedring member58, and anupper collar59 interconnecting thering members57 and58. For manufacturing purposes, thecollar59 and theouter ring member57 may be formed as one component, which may be interconnected with theinner ring member58 by conventional cap screws61. Astatic seal55 seals between theouter ring member57 and thecollar59. An upper supportingsurface51 on thepiston56 is designed for engagement with thelower surface53 of themetal elements48. Accordingly, axial movement of thepiston56 causes corresponding axial and radial movement of the sealing assembly, thereby controlling the closing and opening of the RBOP on a tubular.

Alower flange62 on thepiston56 is provided with aelastomeric seal72 for sealing engagement withadapter ring64.Fluid passageway66 through theadapter ring64 provides continuous fluid communication between openingchamber68 and an annular gap between a radially exterior surface of the adapter ring and an interior surface of thehousing12, as discussed subsequently. Anotherelastomeric seal70 and a backup U-cupelastomeric seal71 provide sealing engagement between an upper end of theadapter ring64 and thepiston56. The spacing between thepiston56 and theadapter ring64, and between theseals70 and72, thus define the openingchamber68. Upper and lower wearbands74 may be provided to centralize thepiston56 within theadapter ring64, and to minimize sliding friction when the piston is moved axially within the adapter ring.

When the sealingassembly46 is rotating in sealed engagement with a tubular, thepiston56 and theadapter ring64 are also rotating members. The adapter ring is guided with respect to theouter housing12 by alower bearing76 and anupper bearing84. When closing the sealingassembly46, pressurized fluid passes throughport26 and throughpassageway88 in thelower housing element14, and then past theseal cartridge96 discussed subsequently and into thechamber90 between the radially outer and radiallyinner ring members57,58 and beneathcollar59 of the piston. As shown on the left side of FIG. 1, pressurized fluid flows under radiallyouter ring member57 of thepiston56, through thebearing76, then up the annular gap between theadapter ring64 and theouter housing element14. Pressurized fluid continues to flow past thebearing84, then through a gap provided between an outer surface of the rotatableinner housing38 and an inner surface of theupper housing16. Sealed engagement between thepiston56 and theadapter ring64 is provided by theseals70,74 and71, and sealed engagement between the adapter ring and the inner housing is provided byelastomeric seal86. Pressurized fluid thus fills thechamber92 surrounding thethrust bearing40, then flows past theflow restriction114, past theupper seal cartridge116, out theport27, then back to thereservoir22.

Sealed engagement between thepiston56 and thelower housing element14 is provided byseal cartridge96 which includesseal98. A suitable lowerrotating seal98 is an elastomeric rotary seal manufactured by Kalsi Engineering. Fluid pressure to the rotating BOP is preferably controlled in response to sensed fluid pressure in the wellbore, which corresponds to the fluid pressure beneath thecartridge96 and between thepiston56 and thelower housing14. Hydraulic fluid pressure to the RBOP is preferably maintained in the range of from about 200 psi to 500 psi greater than wellbore pressure, and accordingly only this limited pressure differential exists across theseal98.

The upper end of theflow passageway88 is closed off withplug87, so that pressurized fluid must flow from thepassageway88 into theannular cavity102, then throughpassageways104 provided in theseal cartridge96. Pressurized fluid then flows upward in an annular gap between theinner piston ring58 and theseal cartridge96, then into thecavity90.Seal cartridge96 does not rotate with the piston, and accordinglystatic seals100 seal between thecartridge96 and thelower housing element14.Spiral retainer ring106 may be used to removably interconnect theseal cartridge96 with thelower housing element14.

High pressure hydraulic fluid within thecavity92 in theupper housing16 is reduced to a low pressure fluid by therestriction member114, which as shown in FIG. 1 comprises a fluid restriction bushing. As more clearly shown in FIG. 2, pressurized fluid from thecavity92 acts on the lower surface of thebushing114.Seal95 provides a static seal between theinner housing sleeve110 and the main body of theinner housing38. These components may be secured together by a plurality ofconventional bolts112. Theupper seal cartridge116 is provided with aseal120 similar to seal98 previously discussed. Jackingholes93 are provided to assist in disassembly.

Pressurized fluid acting on thebushing114 causes a bearingrace support surface130 on the bushing to engage to radiallyouter race117 on thebearing118, forcing thebearing race117 into metal-to-metal engagement withsurface132 onseal cartridge116. At least substantial sealing of the sandwiched outer bearing race causes fluid to flow in the annular gap between a radially innercylindrical surface134 on the bushing and a radially outercylindrical surface136 on theinner housing sleeve110. Bearing118 rotatably guides bushing114 with respect to theinner housing sleeve110. Pressurized fluid is substantially restricted by thebushing114. According to the present invention, therestrictive bushing114 causes a significant pressure drop across the bushing, such that the pressure downstream of the bushing is less than 40% of the pressure upstream of the bushing. More preferably, the pressure drop across thebushing114 is such that the pressure downstream from the bushing is from 10% to 20% of the pressure upstream from the restrictive bushing. This lower pressure fluid then flows through thepassageway119 provided in thecartridge116, then trough thepassageway89 in theupper housing16 and out theport27. Thereplaceable sleeve member122 is secured to theinner housing sleeve110 by retainingring126, and astatic seal124 provides sealed engagement between theinner housing sleeve110 andsleeve member122. Upper and lowerstatic seals101 seal betweencartridge116 and theupper housing element16.

A particular feature of the present invention is that thepiston96 is not provided with rotating seals on the outside diameter of the piston, so that no large diameter rotating seals are required to cause pressurized fluid to actuate the sealingassembly46 and engage the tubular. The diameter of each of the lowerrotating seal element98 and the upperrotating seal element120 is minimized. Each rotating seal has a nominal diameter less than 20% greater than the diameter of thebore32 through the BOP, and preferably less than 10% greater than the diameter of thebore32. A large closing force is generated by the sizable rod area of thepiston56, which is the horizontal cross-sectional area between theseal98 and theseal70. A comparatively small flange area of the piston, which is the horizontal cross-sectional area between theseal70 and theseal72, is used to open the sealing assembly, as explained subsequently.

During rotation of theseal assembly46, therestrictive bushing114 floats radially with theinner housing sleeve110 to accommodate eccentricity without generating excessive friction. Therestrictive bushing114 is thus structurally interconnected with the rotatableinner housing sleeve110 by thebearing118, so that a uniform gap is maintained between the outer cylindrical surface on the inner housing and the inner cylindrical surface on the restrictive bushing. Eccentricity between the rotatableinner housing sleeve110 and theouter housing12 will thus not cause a variation in the radial spacing between the outercylindrical surface134 on thebushing114 and the innercylindrical surface136 on theinner housing38. Therestriction bushing114 is fabricated from a rigid material, such as steel, bronze or a durable ceramic.Restrictive bushing114 preferably fits between cylindrical surfaces on the stationary upper housing and the rotating inner housing which are each substantially concentric with the central axis of the RBOP. This design is preferred compared to providing a restrictive bushing between spaced substantially horizontal surfaces on theupper housing16 and the rotatableinner housing38.

The void above theseal120 and in the annulus between the tubular T and thecylindrical surface34 on theupper housing16 will typically be open to atmospheric pressure. Preferably,restrictive bushing114 drops the pressure exposed to theseal120 such that pressure downstream from thebushing114 is in a range from 100 psi to 500 psi above atmospheric pressure. This pressure may be reliably maintained by theseal120 over a relatively long service life of the RBOP. Theseal cartridges116 and96 may be easily replaced during periodic service on the BOP, if required. Eachrotating seal98 and120 is mounted on a metal seal cartridge ring which includes radial passageways therethrough for transmitting hydraulic fluid past the seal cartridge.

It may be seen that the diameter of the upperrotating seal120 is preferably substantially the same as the diameter of the lowerrotating seal98 so as to balance the pressure acting on the rotating assembly. When the sealingassembly46 is in sealed engagement with a rotating tubular, theinner housing38, theadapter ring64 and thepiston56 thus rotate as an assembly. Thethrust bearing40 opposes the upward force from thepiston56 acting against the rotatinginner housing38 through the sealingassembly46. To reduce the size of theassembly10, thethrust bearing40 is preferably spaced radially outward of theflow restriction member114. The inner housing thrust bearing40 is also provided within a horizontal plane which is inclusive of the flow restriction member, thereby reducing the height of the RBOP.

To open the sealingassembly46, pressurized fluid is supplied throughlines24 to thefluid opening port28, then throughpassageway94 and intochamber92. During opening, the fluid control system blocks fluid from flowing outport27. The hydraulic fluid will flow in the annulus between theinner housing38 and theupper housing16, then down the annulus between theadapter ring64 and thelower housing14. Pressurized fluid in thecavity92 acting on theinner housing38 forces the inner housing downward, which also forces theadapter ring64 downward. This axial movement of the adapter ring is relatively small, e.g., from “0.010 to 0.050”, although this movement is important as explained below.

As shown in FIG. 3, pressurized fluid in fluidopen port28 forces a lower surface78 on theadapter ring64 into engagement with anupper surface80 on theinner race82 of thebearing76, thereby substantially restricting fluid flow past thebearing76. When opening the BOP, theinner housing38, theadapter ring64 and thepiston96 are not rotating, so that engagement of thesurfaces78 and80 is static. Accordingly, pressure in thecavity90 is significantly lower than the pressure in thecavity92 during opening of the BOP. Fluid which flows past the bearing76 then flows in the gap between thelower housing element14 and alower surface83 on the piston, then past the inner rotatinglower seal98 and out thepert port26.

When pressurized fluid is supplied topert port28 to open the RBOP, high frictional forces are not encountered within theassembly10. It should be understood that when closing pressure is supplied to the RBOP throughport26, theadapter ring64 is forced upward slightly into engagement with the rotatinginner housing38, thereby separating thesurface78 and80 so that fluid flows freely up intocavity92.

FIG. 4 depicts an alternative embodiment of a flow restriction member and an upper rotary seal. The embodiment as shown in FIG. 4 is similar to the embodiment as shown in FIG. 2, and accordingly like reference numerals are used to depict like components. As shown in FIG. 4, the flow restrictive bushing has been replaced with a plurality of labyrinth rings. Theflow restriction member138 comprises a plurality of axially spaced static carrier rings140 each supporting a metalflow restriction ring142 thereon. Therings142 significantly reduce the pressure drop across theflow restriction member138. Atop ring152 includes circumferentially spacedflow ports154 for passing restricted fluid topassageway89.Static seals156 seal between the carder carrier rings140. Carrier rings140 remain in a fixed position relative to theupper housing16, while therings142 each move radially with respect to the carrier rings to float and thereby accommodate eccentricity between thestationary housing16 and the rotatableinner housing sleeve110. Therings142 preferably are fabricated from bronze, although steel or ceramic material rings may be used. The restricted pressure fluid in thepassageways154 then flows past thecartridge seal146 then out thepassageway89 as previously described. Theupper cartridge seal146 includes anelastomeric sealing member148 which seals the restricted pressure fluid from atmospheric pressure.

The rotating blowout preventer of the present invention may be used to provide reliable sealing engagement with a tubular within a wellbore having a pressure in excess of approximately 2000 psi while the tubular is rotating at speeds of up to approximately 200 rpm. A BOP capable of such reliable operation has long been desired by those skilled in the art. When the tubular is not rotating,assembly46 may reliable seal with a tubular when the wellbore pressure is in excess of 5000 psi. As previously noted, theassembly10 also has the ability for complete shutoff from the wellbore when no tubular is passing through the RBOP and the wellbore is at a pressure of up to 2500 psi.

According to the method of the invention, the lower rotary seal between the piston and the lower housing seals the differential pressure between the supplied hydraulic fluid pressure and the pressure in the well. As noted above, the hydraulic pressure may be controlled by conventional techniques so that this pressure differential is less than 500 psi. To seal between the rotating inner housing and the upper stationary housing, this hydraulic pressure is significantly reduced by at least 60%, so that the upper rotary seal is exposed to less than 40% of the pressure supplied to the lower rotating seals. The flow restriction is guided to maintain a substantially uniform gap between a radially inward surface of the flow restriction and a radially outward surface of the rotatable inner housing. The inner housing bearing is also positioned to reduce the size of the assembly, as explained above.

While the beating bearing118 is preferred for maintaining a uniform gap between the flow restriction member and the rotatable inner housing, a spacing member other than a bearing could be used to maintain this uniform gap and thereby compensate for limited eccentricity between the rotatable inner housing and the stationary housing. While a fluid-tight seal between an upper surface of the flow restriction member and the upper seal cartridge is not essential, it is important that substantially all the hydraulic fluid passing by the flow restriction member pass through this uniform gap maintained by the bearing118 or other suitable spacing member. This fluid-fight fluid-tightseal between the flow restriction member and the upper seal cartridge may be made directly, i.e., without sandwiching the bearing race therebetween.

Those skilled in the art will also appreciate that some type of fluid restriction other than the engagement ofsurfaces78 and80 on theadapter ring64 and thebearing76 may be used to create pressure in the openingchamber68 which is greater than the pressure inchamber90 when fluid pressure is applied to open the RBOP. The techniques as disclosed herein are relatively simple, however, and are considered highly reliable.

Various further modifications in theassembly10 may be made. For example, the ranged flanged connection between the upper and lower housings could be made with a quick release clamp mechanism, thereby facilitating easy change-out of the sealing elements. The inner housing and the inner housing sleeve are preferably fabricated as separate components since the sleeve may become dented or bent during use of the BOP. Less desirably, the inner housing could include a sleeve integral therewith. The foregoing disclosure and description of the invention are thus illustrative and explanatory of preferred embodiments. Various changes in the structure of the RBOP as well as in the method of operating the RBOP will be made without departing from the scope of the invention, which is defined by depending the pending claims.

Claims (29)

What is claimed is:

1. A rotatable blowout preventer for use in a hydrocarbon recovery operation sealing pressure in a well including a tubular member passing through the blowout preventer, the rotatable blowout preventer assembly comprising:

a stationary outer housing defining a bore therein for receiving the tubular member, the outer housing have a central axis generally concentric with an axis of the tubular member, and the outer housing including a fluid closing input port and a fluid output port therein;

an inner housing rotatable within the outer housing and having an inner curved surface thereon substantially defined by a portion of a sphere having a center substantially adjacent the central axis of the bore ;

an annular sealing assembly supported within the inner housing for sealed engagement with the tubular member, a sealing assembly including a plurality of rigid elements circumferentially arranged about the bore of the outer housing, each rigid element having an outer surface for sliding engagement with the inner curved surface of the inner housing, and the sealing assembly including a resilient member for sealed engagement with the tubular member;

a rotatable piston axially movable within the outer housing in response to pressurized fluid in the fluid closing port for causing both axial and radial movement of the annular sealing assembly;

a lower rotary seal between the piston and a lower portion of the stationary outer housing for sealing pressurized fluid within the stationary outer housing from a lower end of the bore in the outer housing;

a flow restriction member between the rotatable inner housing and an upper portion of the stationary outer housing for reducing fluid pressure downstream of the flow restriction member to less than 40% of the pressure upstream from the flow restriction member; and

an upper rotary seal between the rotatable inner housing and the upper portion of the stationary outer housing and downstream from the flow restriction member for sealing the reduced pressure fluid within the outer housing from an upper end of the bore in the outer housing.

2. The rotary blowout preventer as defined inclaim 1, further comprising:

an inner housing bearing for rotatably guiding rotation of the inner housing relative to the outer housing, the inner housing bearing being spaced radially outward from the flow restriction member and within a plane perpendicular to the central axis of the bore and inclusive of the flow restriction member.

3. The rotary blowout preventer as defined inclaim 1, wherein the flow restriction member is selected from the material consisting of bronze, steel, and ceramic.

4. The rotary blowout preventer as defined inclaim 1, further comprising:

a restriction member bearing for guiding rotation of the flow restriction member relative to the inner housing while maintaining a substantially uniform gap between a radially inward surface of the flow restriction member and a radially outward surface of the rotatable inner housing.

5. The rotary blowout preventer as defined inclaim 1, further comprising:

the flow restriction member is spaced between a radially outward cylindrical surface of the rotatable inner housing and a radially inward cylindrical surface of the outer housing; and

a spacing member for radially spacing the flow restriction member relative to the inner housing to maintain a substantially uniform gap between a radially inward surface of the flow restriction member and the radially outward surface of the rotatable inner housing, such that eccentricity between the inner housing and the outer housing varies a radial spacing between a radially outer surface of the flow restriction member and the radially inward surface of the outer housing.

6. The rotary blowout preventer as defined inclaim 1, wherein:

each of the lower rotary seal and the upper rotary seal have a diameter less than 20% greater than a diameter of the bore in the stationary outer housing.

7. The rotary blowout preventer as defined inclaim 1, further comprising:

a fluid flow path between the fluid closing input port and the fluid output port, the fluid flow path passing by fluid to the lower rotary seal, radially outward of the piston, radially outward of the rotatable inner housing, past then through the flow restriction member, past then to the upper rotary seal, and then through the fluid output port.

8. The rotary blowout preventer as defined inclaim 1, further comprising:

a rotatable piston axially movable within the outer housing in response to pressurized fluid in the fluid closing port for causing both axial and radial movement of the annular sealing assembly;

a rotatable adapter ring radially outward of the piston;

an upper adapter seal for sealed engagement between the piston and the adapter ring;

a lower adapter seal for sealed engagement between the piston and the adapter ring;

an opening chamber between the piston and the adapter ring and between the upper and lower adapter seals for receiving pressurized fluid from a fluid opening port in the outer housing to move the annular sealing assembly to an open position; and

a bearing member for guiding rotation of the adapter ring with respect to the outer housing, the bearing member and the adapter ring each having a metal surface thereon moved into engagement by pressurized fluid in the fluid opening port for substantially restricting fluid flow from the fluid opening port to the fluid closing port.

9. A rotatable blowout preventer system for use in a hydrocarbon recovery operation including a tubular member passing through the blowout preventer, the rotatable blowout preventer system comprising:

a stationary outer housing defining a bore therein for receiving the tubular member, the outer housing having a central axis generally concentric with an axis of the tubular member, and the outer housing including a fluid closing port, a fluid opening port, and a fluid output port therein;

an inner housing rotatable within the outer housing;

an annular sealing assembly supported within the inner housing for sealed engagement with the tubular member;

a pump for generating pressurized hydraulic fluid;

a control valve for selectively controlling flow of the pressurized hydraulic fluid to one of the fluid closing port and fluid opening port;

a rotatable piston axially movable within the outer housing in response to pressurized fluid in the fluid closing port for causing radially inward movement to the annular sealing assembly;

a rotatable adapter ring radially outward of the piston;

an upper adapter seal for sealed engagement between the piston and the adapter ring;

a lower adapter seal for sealed engagement between the piston and the adapter ring;

an opening chamber between the piston and the adapter ring and between the upper and lower seals for receiving pressurized fluid from the fluid opening port to move the piston and the annular sealing assembly to an open position;

a lower rotary seal between the piston and a lower portion of the stationary outer housing for sealing pressurized fluid within the stationary outer housing from a lower end of the bore in the outer housing;

a flow restriction member between the rotatable inner housing and an upper portion of the stationary outer housing for reducing fluid pressure downstream of the flow restriction member; and

a upper rotary seal between the rotatable inner housing and the upper portion of the stationary outer housing and downstream from the flow restriction member for sealing the reduced pressure fluid within the outer housing from a upper end of the bore in the outer housing.

10. The rotary blowout preventer system as defined inclaim 9, further comprising:

an inner housing bearing for rotatably guiding rotation of the inner housing relative to the outer housing, the inner housing bearing being spaced radially outward from the flow restriction member and within a plane perpendicular to the central axis of the bore and inclusive of the flow restriction member.

11. The rotary blowout preventer system as defined inclaim 9, further comprising:

a restriction member bearing for guiding rotation of the flow restriction member relative to the inner housing while maintaining a substantially uniform gap between a radially inward surface of the flow restriction member and a radially outward surface of the rotatable inner housing.

12. The rotary blowout preventer system as defined inclaim 9, further comprising:

the flow restriction member is spaced between a radially outward cylindrical surface of the rotatable inner housing and a radially inward cylindrical surface of the outer housing; and

a spacing member for radially spacing the flow restriction member relative to the inner housing to maintain a substantially uniform gap between a radially inward surface of the flow restriction member and the radially outward surface of the rotatable inner housing, such that eccentricity between the inner housing and the outer housing varies a radial spacing between a radially outer surface of the flow restriction member and the radially inward surface of the outer housing.

13. The rotary blowout preventer system as defined inclaim 9, wherein:

a lower seal cartridge ring for supporting the lower rotary seal thereon;

an upper seal cartridge ring for supporting the upper rotary seal thereon; and

each of the lower rotary seal and the upper rotary seal have a diameter less than 20% greater than a diameter of the bore in the stationary outer housing.

14. A rotary blowout preventer system as defined inclaim 9, further comprising:

a lower seal cartridge ring for supporting the lower rotary seal thereon, the lower cartridge ring having a passageway therethrough;

an upper seal cartridge ring for supporting the upper rotary seal thereon, the upper cartridge ring having a passageway therethrough; and

a fluid flow path between the fluid closing port and the fluid output port, the fluid flow path passing through the passageway in the lower seal cartridge ring, radially outward of the piston, radially outward of the rotatable inner housing, past the flow restriction member, through the passageway in the upper seal cartridge ring, and then through the fluid output port.

15. The rotary blowout preventer system as defined inclaim 9, further comprising:

the adapter ring being axially movable in response to fluid pressure in the fluid opening port to substantially restrict fluid flow from the fluid opening port to the fluid closing port.

16. A method of controlling actuation of a rotatable blowout preventer for for use in a hydrocarbon recovery operation sealing pressure in a well including a tubular member passing through the blowout preventer, the rotatable blowout preventer including a stationary outer housing defining a bore therein for receiving the tubular member, an inner housing rotatable within the outer housing, an annular sealing assembly supported within the inner housing for sealed engagement with the tubular member, a piston movable within the outer housing for causing radial movement of the annular sealing assembly, and a fluid closing input port and a fluid output port in the outer housing for passing pressurized fluid to the piston through the rotatable blowout preventer, the method comprising:

providing a lower rotary seal between the piston and a lower portion of the outer housing for sealing pressurized fluid within the stationary outer housing from a lower end of the bore in the outer housing;

providing a flow restriction between the rotatable inner housing and an upper portion of the stationary outer housing for reducing fluid pressure downstream of the flow restriction member to less than 40% of the pressure upstream from the flow restriction; and

providing an upper rotary seal between the rotatable inner housing and an upper portion of the stationary outer housing and the downstream from the flow restriction for sealing the reduced pressure fluid within the stationary outer housing from an upper end of the bore in the outer housing.

17. The method as defined inclaim 16, further comprising:

providing an inner housing bearing for rotatably guiding rotation of the inner housing relative to the outer housing; and

spacing the inner housing bearing radially outward from the flow restriction and within a plane inclusive of the flow restriction.

18. The method as defined inclaim 16, further comprising:

guiding rotation of the flow restriction relative to the inner housing while maintaining a substantially uniform gap between a radially inward surface of the flow restriction and a radially outward surface of the rotatable inner housing.

19. The method as defined inclaim 16, further comprising:

forming a flow path between the fluid closing input port and the fluid output port, the flow path passing by fluid to the lower rotary seal, radially outward of the piston, radially outward of the rotatable inner housing, past through the flow restriction, past to the upper rotary seal, and then through the fluid output port.

20. The method as defined inclaim 16, further comprising:

providing a piston removable within the outer housing for causing radial movement of the annular sealing assembly;

providing a rotatable adapter ring radially outward of the piston;

providing an upper adapter seal for sealed engagement between the piston and the adapter ring;

providing a lower adapter seal for sealed engagement between the piston and the adapter ring;

forming an opening chamber between the piston and the adapter ring and between the upper and lower adapter seals;

passing pressurized fluid through a fluid opening port in the outer housing to move the piston and the annular packer assembly to an open position; and

substantially restricting fluid flow from the fluid opening port to the fluid closing port downstream from the opening chamber.

21. The rotatable blowout preventer as defined inclaim 1;

the inner housing having an inner curved surface thereon substantially defined by a portion of a sphere having a center substantially adjacent the central axis of the bore; and

the annular sealing assembly includes that plurality of rigid elements circumferentially arranged about the bore of the outer housing, each rigid element having an outer surface of a sliding engagement with the inner curved surface of the inner housing.

22. The rotary blowout preventer as defined inclaim 21, further comprising:

a rotatable piston axially moveable within the outer housing in response to pressurized fluid for causing both axially and radially movement of the annular sealing assembly.

23. The rotary blowout preventer as defined inclaim 22, wherein the lower rotary seal acts between the piston and a lower portion of the stationary outer housing.

24. The sealing assembly as defined inclaim 1, wherein the upper rotary seal is positioned between the rotatable inner housing and an upper portion of the stationary outer housing.

25. The rotary blowout preventer as defined inclaim 1, wherein the flow restriction member is spaced between a cylindrical surface on the stationary upper housing and another cylindrical surface on the rotatable inner housing.

26. The rotary blowout preventer as defined inclaim 1, wherein an inner surface of the annular sealing preventer is configured for closing off flow of fluid through the annular sealing assembly when no tubular member passes through the blowout preventer.

27. The method as defined inclaim 16, wherein the upper rotary seal is spaced between the rotary inner housing and an upper portion of the stationary outer housing.

28. The method as defined inclaim 16, further comprising:

positioning the flow restriction between the cylindrical surface on the stationary upper housing and another cylindrical surface on the rotary inner housing.

29. The method as defined inclaim 16, further comprising:

closing the annular inner sealing assembly to prevent fluid from passing therethrough when the tubular member does not pass through the blowout preventer.

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