CROSS-REFERENCE TO RELATED APPLICATIONS
FIELD OF THE INVENTION
This application claims priority to Provisional Application Ser. No. 60/827,319, filed Sep. 28, 2006, the entire contents of which are incorporated herein by reference.
This invention relates generally to oil and/or gas production and more specifically to a combination pump rod clamp and blowout preventer (BOP) for oil, gas, or water wells, and in particular to a pump rod clamp/blowout preventer having a pump rod clamping or gripping capability sufficient to support a pump rod and providing enhanced safety from static charge buildup.
Blowout preventers (BOPs) and pump rod clamps (aka polished rod clamps) have been generally known in the art for some time. Pump rod clamps are used to suspend the rod within the well, and/or to prevent rotational movement of the pump rod. Many types of pump rod clamps are known. Some rod clamps use a pair of rams that are driven radially inward to contact the pump rod and hold it in place. Others use wedges inserted around the rod. Still others use a pair of rams that can be bolted around the exterior surface of the rod and hung from a mandrel or other support member.
BOPs are used to seal off the well and contain its contents under a variety of different situations. For example, during the servicing of a wellhead one or more blowout preventers are often used to seal against the pump or polished rod to contain the contents of the well when downstream equipment is removed or disassembled for servicing. In other instances blowout preventers may be used to seal off a well where the pump rod is removed, or in the event of a failure of the pump rod. Blowout preventers typically include a pair of rams that are received within cylinders extending through a BOP housing and situated generally perpendicular to the longitudinal axis of the well casing. Typically the end of each ram has a semi-circular channel on its face to allow it to seal against the exterior surface of the pump rod when the BOP is actuated by driving the rams inward. The faces of the rams may include an elastomer or other sealing mechanism to ensure that a fluid tight seal is created when the rams fully engage the pump rod.
Generally, BOPs and pump rod clamps are separate pieces of equipment. The BOP is typically capable of sealingly engaging the pump rod to prevent blow out, but does not engage the rod forcefully enough to suspend the rod or prevent the rod from rotating. Thus a rod clamp is required for this duty. Likewise, though rod clamps grip the rod forcefully enough to suspend the rod or prevent its rotation, the engagement between the rod clamp and the rod is not typically a sealing engagement and thus does not prevent the contents of the well from escaping. Thus, there is a need for a single piece of equipment that can serve double-duty as both a pump rod clamp and a BOP.
Recent disclosures have purported to describe particular embodiments of combination BOP/well rod clamp devices. One example is U.S. Pat. No. 7,000,888, by Wright et al., (“the '888 patent”) the entire contents of which are incorporated herein by reference. The '888 patent describes a pump rod clamp having rams featuring arcuate channels to sealingly engage a pump rod. The rams include one or more gripping inserts releasably secured to the rams, or a non-metallic coating applied to the rams, providing an electrically insulating barrier between the pump rod clamp and the pump rod.
U.S. Pat. No. 6,843,313, by Hult (“the '313 patent”) and related U.S. Patent Application Publication No. 2005/0045323 A1, describe a pump drive head for a progressing cavity pump that includes a pump rod lock-out clamp that is integral with or adjacent to a blow-out-preventer. One embodiment described in these references includes a BOP that serves as a lock out clamp for well servicing. The BOP/lock-out clamp includes metal pistons that are forced against the pump rod to grippingly engage in metal-to-metal contact. The inner end of the pistons includes an arcuate recess with curvature corresponding to the pump rod. The pistons also include a narrow elastomeric seal running across the vertical flat face of the piston, along the arcuate recess, along the mid height of the piston and then circumferentially around the piston. The elastomeric seals seal between the pistons, between the pistons and the pump rod, and between the pistons and the piston bores, thereby preventing fluid from escaping up the well bore when the pistons are engaged with the pump rod. The entire contents of the '313 patent and U.S. Patent Application Publication No. 2005/0045323 A1 are incorporated herein by reference.
Disclosed herein is a combination pump rod clamp/BOP. The pump rod clamp/BOP has a housing having a lateral bore for receiving a pump rod. Rams are contained in the housing for engaging the pump rod with strength capable of supporting the weight of the pump rod and preventing axial or rotational movement of the rod. When the pump rod clamp/BOP is activated, i.e., when the rams are engaged with the pump rod, the rams also seal off the lateral bore, preventing fluids from escaping from the well through the bore.
BRIEF DESCRIPTION OF THE DRAWINGS
The rams have an arcuate channel for clamping the pump rod and also include a gripping non-metallic material non-releasably disposed on the face of the ram. The non-metallic material can coat the entire leading face of the ram, the arcuate channel only, or part of the arcuate channel. These and other features will be apparent in view of the below description and the attached drawings.
FIG. 1A illustrates a pump rod clamp/BOP in a deactivated position.
FIG. 1B illustrates a pump rod clamp/BOP in an engaged (activated) position.
FIG. 2 illustrates a ram for a pump rod clamp/BOP, the ram having a non-metallic gripping material non-releasably disposed thereon.
FIG. 3 illustrates a top-down view of rams engaging a pump rod, as when a pump rod clamp/BOP is in an activated position.
FIG. 4 illustrates a ram for pump rod clamp/BOP having a non-metallic non-releasable insert.
In the FIGS. like numbers represent like elements. FIGS. 1A and 1B illustrate a BOP/pump rod clamp according to the present disclosure. Pump rod clamp/BOP 1 includes a central housing 2 having a longitudinal bore 3 extending through the central housing 2 for receiving a pump rod 4. Central housing 2 may contain upper and lower flanges or threaded connections, 5 and 6 respectively, for mounting the housing to wellhead equipment. As is common with most blowout preventers, central housing 2 further includes a pair of opposed radial bores 7 and 8 that are generally perpendicular to, and that terminate at, longitudinal bore 3. Rams 9 and 10 are slidably received within bores 7 and 8. One or more actuators 11 are used to move rams 9 and 10 between a deactivated position FIG. 1A wherein rams 9 and 10 do not engage the exterior surface of the pump rod and an activated position wherein rams 9 and 10 extend into longitudinal bore 7 and 8 and grippingly engage the exterior surface of the pump rod 4. Any of a variety of actuators may be used to move the rams between their activated and deactivated positions. Such mechanisms include manual, hydraulic, pneumatic, or electric actuators. In the embodiment shown, actuators 11 include stems 12 that can be threadably received within the actuators. The inner most ends of the stems 12 are attached to rams 9 and 10 and are free to rotate with respect to the rams. Stems 12 can be rotated manually, electrically, pneumatically, or the like to move rams 9 and 10 between engaged and disengaged positions.
FIG. 2 illustrates a ram 9, having a engaging face 21 directed generally toward longitudinal bore 3 (and hence toward the exterior surface of a pump rod received within the longitudinal bore). Leading face 21 includes an arcuate channel 22 in general alignment with longitudinal bore 3 and a pump rod received therein. Arcuate channel 22 is positioned in such a manner that, when the rams are moved inwardly to their activated position, arcuate channel 22 encompasses the pump rod and grippingly engages the exterior surface of the rod.
Engaging face 21 includes a non-releasable non-metallic material 23 for making contact with the pump rod to securely hold the rod in place when the rams are moved to their activated position. FIG. 3 illustrates a top-down cross sectional view of rams 9 and 10 engaging a pump rod 4. Non-metallic material 23 makes contact with pump rod 4 and holds the rod in place. Leading faces 21 sealingly engage each other, thereby preventing fluids from escaping up bore 3. The non-metallic gripping material can be disposed only (or substantially only) in the arcuate channel as shown in FIG. 2 or can partially or totally coat the entire leading face 21.
FIG. 4 illustrates an alternative embodiment of ram 9 including gripping inserts 41 disposed in arcuate channel 22. Gripping inserts 41 can be made of any suitable non-metallic material, as described above. Gripping inserts 41 are joined to ram 9 using any suitable non-releasable method. For example, gripping inserts 41 can be non-releasably press-fit into receiving cavities machined into arcuate channel 22.
The non-metallic material can be any non-metallic material suitable for grippingly engaging a pump rod. The non-metallic material presents a hard surface for engaging the exterior of the pump rod without scoring or galling the rod. Traditional rod clamps that permit metal-to-metal contact often gall the surface of the rod and create burs, ridges, and other marks that can rip or tear packing material when the rod is pulled from the well. The non-metallic material reduces the likelihood of damage to the exterior of the rod. The non-metallic material can have a slightly roughened texture. As used herein, non-metallic material refers to materials that are not metals or alloys.
Suitable non-metallic materials include elastomers such as rubbers, polymers, and the like, ceramics, carbides, nitrides, composites, metal oxides, etc. Composites commonly used for automobile break shoes are particularly suitable. Such materials include chrysotile materials, metal oxides, and composites containing metal oxides. Metal oxides, such as aluminum oxide are also particularly suitable.
The non-metallic material can be affixed to the rams by any suitable non-releasable method. For example, the material can be glued to the ram using a durable gluing material such as a resin, epoxy, or the like. If the non-metallic material is amenable to brazing, as in the case of carbides, for example, brazing can be used. Non-releasably form fitting, press fitting, molding, or interference fitting can also be used. The non-metallic material can be deposited directly on the ram, spray coated onto the ram, or deposited chemically onto the ram, etc. According to one embodiment, the arcuate channel includes pockets for receiving a band of the non-metallic material. The non-metallic material can be press fit, or otherwise non-releasably disposed within the pockets, as shown in FIG. 4. Generally the methods of applying the non-metallic material to the rams in a non-releasable manner provide a high degree of rigidity in the structure.
The non-metallic material may or may not provide an insulating barrier between the rams and the pump rod and/or between the pump rod and the pump rod clamp/BOP. According to one embodiment, the non-metallic material does not provide such electrical insulation. In such an embodiment, the pump rod and the pump rod clamp/BOP may be maintained in electrical equilibrium (i.e., electrical contact is provided between the pump rod clamp/BOP and the pump rod) to prevent static charge buildup between the pump rod and the pump rod clamp/BOP. Such electrical equilibrium may be provided by a shunt wire, Conductive coatins, conductive seals, one or more metallic tabs, non-grippingly engaging metallic round nose spring plunger, or the like to maintain electrical equilibrium between the pump rod and the housing of the pump rod clamp/BOP.
It should be understood that the inventive concepts disclosed herein are capable of many modifications. To the extent such modifications fall within the scope of the appended claims and their equivalents, they are intended to be covered by this patent.