Triple valve blow out preventer

[0001] The current application is a continuation-in-part of U.S. patent application Ser. No. 10/971,468, filed Oct. 21, 2004, now U.S. Pat. No. 7,121,295, which claims priority from U.S. Provisional Application No. 60/513,252, filed Oct. 21, 2003, the disclosures of which are incorporated herein by reference.

[0002] The current invention is directed to internal blow out preventers; and more particularly to a triple valve internal blow out preventer having improved reliability and durability.

[0003] Internal Blow Out Preventers (IBOPs) are ball valves designed to relieve pressure and prevent blow out in high pressure drilling applications. However, these blow out preventers often fail in the field due to the high velocity mud flowing down and periodic hydrostatic testing of the IBOP valve, which is often exposed to pressures up to 16,000 psi. These hydrostatic pressures apply large loads to the valves causing them to fail.

[0004] Typically, blow-out preventers have included a dual-valve configuration comprising two separate assemblies an upper and lower blow-out preventer, which each have a single blow-out preventer valve. The redundancy of two valves is required because of the very high-pressures used and the high cycle use these valves are put through as mud saver valves. Unfortunately, the seals on these valves are subject to high strain and use and are subject to frequent failure. Because a back-up valve is always required in case of failure if a single one of these valves fails either the entire unit must be replaced, or the unit must be shut-down while repairs are performed. Neither of these options is particularly appealing because of the consumption of time and money on the drill site. Unfortunately, because of size constraints in some topdrive systems inserting an additional redundant valve between the upper and lower IBOP assemblies has not been considered feasible.

[0005] Accordingly, a need exists for an improved internal blow out preventer with improved durability and redundancy.

[0006] This invention is directed to a triple valve internal blow out preventer with improved durability, and its use in drilling applications.

[0007] In one embodiment, the triple valve internal blow out preventer comprises a single body comprising three individual blow out preventer ball valves and ball valve seats contained therein.

[0008] In another embodiment, the ball valve and ball valve seat are stepped in the direction of the mud-flow such that the edge of the ball valve exposed to the mud flow is setback from the edge of the seat.

[0009] In still another embodiment, the internal blow out preventer is coated with tungsten carbide. In one such embodiment, the tungsten carbide coating is wrapped about the edge of the one of either the ball valve or the seat.

[0010] In one embodiment, each of the ball valves includes a tubular assembly having a central passageway with upper and lower seats mounted therein. A ball is rotatably received between the upper and lower seats and includes an external surface and a central opening, wherein the central opening includes an undercut. A protective coating is applied to both the external surface and the undercut.

[0011] In another embodiment, each of the ball valves includes a tubular assembly having a central passageway with upper and lower seats mounted therein. A ball is rotatably received between the upper and lower seats, and includes a central opening and an upper contacting surface that contacts a contacting surface of the upper seat. The central opening includes an upper undercut at an upper end of the ball. A protective coating is applied to both the upper contacting surface and the upper undercut of the ball.

[0022] The current invention is directed to a unitary triple-valve internal blow out preventer or IBOP having increased reliability and durability.

[0023] FIG. 1 shows a triple valve internal blow out preventer 10 according to an exemplary embodiment of the present invention. The internal blow out preventer 10 provides a pressure check valve to prevent the blow out of an oil and gas well from a back pressure build-up during drilling operations. In one embodiment, the internal blow out preventer 10 is threadably connected to a drill string 16, and is driven by a top drive system 18 during a drilling operation.

[0024] As shown in FIG. 2a, a conventional IBOP comprises two separate assemblies, an upper 11a and lower 11b tubular assembly, each having a single blow-out preventer valve 12a and 12b disposed therein. These assemblies can each be threadably attached in line with suitable tubulars 16a and 16b in a drilling operation.

[0025] In contrast, the IBOP in accordance with the current invention, as shown in FIG. 2b, is designed to provide a unitary triple-valve pressure relief assembly 10 to prevent the blow out of the well from a back pressure build-up during drilling. In the embodiment shown in FIG. 2b, the triple-valve blow-out preventer of the current invention is shown in cross-section. As shown, the assembly 10 includes three ball valves 12a to 12c set in series for diverting pressurized flow in a blow out situation, arranged and rotatably retained in a corresponding ball seat 13a to 13c. Although a single unitary body is used to retain all three of the valves, for clarity we will divide the body into an upper portion 25a and a lower portion 25b separated by a metal cuff 25c. The lower portion 25b of the IBOP of the current invention contains a single valve 12c, which is formed by positioning a lower end of the lower seat 24c in abutment with a shoulder 27c of the metal cuff 25c in the lower portion 25b of the central passageway; positioning a lower end of the ball 20c in abutment with an upper end of the lower seat 24c; and placing a lower end of the upper seat 22c in abutment with an upper end of the ball 20c. In one embodiment, the upper seat 22c includes threads 21c that threadably engage threads 22c in the the central passageway of the valve assembly 12c in order to prevent vertical displacement of itself, as well as the ball 20c and the lower seat 24c. Similar constructions are used for the valves 12a and 12b in the upper portion 25a of the central passageway, except that an insertable seat ring 9b is used to replace the upper seat of the lower valve 12b and a second insertable seat ring 9a is used to replace the lower seat of the upper valve 12a such that seat rings 9a and 9b directly abut one another within the upper central passageway 25a of the IBOP. Such construction allows for the removal of both the upper valves 12a and 12b in case of a breakdown.

[0026] Detailed views of the construction of one exemplary valve are provided in FIGS. 3 to 7. For example, FIG. 3 shows an exploded view of an exemplary ball valve in accordance with the current invention. As shown, each of the valves 12 includes a valve assembly 13 having an upper seat 22 and a lower seat 24 mounted therein. The upper seat 22 is mounted in a threaded connection 21 within the valve assembly 13, and the lower seat 24 is mounted against a shoulder 27 in the valve assembly 13. A ball 20 is rotatably received between the upper and lower seats 22 and 24. The valve assembly 13 and the upper and lower seats 22 and 24 together form each of the ball valves 12. Each of the valves 12 are mounted in a central passageway and each of the ball 20 and seats 22 and 24 of the valves 12 each have central openings 36, 38 and 40 axially aligned with each other and with the longitudinal axis of the central passageway 25. As shown by the arrow, during operation, when all valves are open, drilling mud flows downwardly through each of the valve openings 36, 38 and 40 creating a mud flow bath through the IBOP.

[0027] In order to improve the fluid flow of the drilling mud through the internal blow out preventer 10, in one embodiment shown for example in FIG. 3, the diameter of the central opening 38 in the ball 20 may also be made slightly larger than the diameter of the central opening 36 in the upper seat 22 (see FIG. 4); and the diameter of the central opening 40 in the lower seat 24 may be made slightly larger than the diameter of the central opening 38 in the ball 20 (see FIG. 5). In such an arrangement, the drilling mud is able to flow smoothly from the central opening 36 in the upper seat 22 to the slightly larger central opening 38 in the ball 20 and smoothly flow from the central opening 38 in the ball 20 to the slightly larger central opening 40 in the lower seat 24. In addition, this arrangement lessens the impact of the mud flow on the upper ball junction 50 (since the junction 50 is inset from the central opening 36 of the upper seat 22) and thereby further reduces the likelihood of the protective coating 40 peeling away at the upper ball junction 50.

[0028] In another embodiment, the IBOP design of the current invention may also include shrouded tungsten carbide edges for the ball. In this embodiment, the edges of the ball where the tungsten carbide runs out in conventional designs has been improved by wrapping the carbide coating from the spherical surface into the bore uniformly without leaving an edge. The carbide coating thus extends on both ends of the shrouding it into the bore smoothly assuring that the mudflow does not erode and peal away the coating at a vulnerable edge. FIGS. 4 and 5 show exploded views of the contact surfaces of the seats set out in circled elements 4 and 5 of FIG. 3. As shown in FIGS. 4 and 5, with the ball 20 and seats 22 and 24 positioned as described above, the ball 20 has an upper contact surface 26 that contacts a contact surface 28 of the upper seat 22; and a lower contact surface 30 that contacts a contact surface 32 of the lower seat 34. In order to reduce wear between these surfaces, each contact surface 26, 28, 30 and 32 is coated with a protective coating (shown for example in FIG. 7, as protective coating 40). The protective coating may be applied by any appropriate coating method and the protective coating may be any coating appropriate for reducing wear. For example, in one embodiment, the protective coating is a hard protective coating such as tungsten carbide.

[0029] As described above, a problem with internal blow out preventers of the prior art is that a protective coating is applied to the external surface of the ball, but does not extend into the central opening of the ball. As a result the coating often peels off of the ball valve at the junction of the external surface of the ball and the central opening of the ball. As show in FIG. 6, in one embodiment according to the present invention, an undercut 51 and 53 is cut into the upper and lower ends, respectively, of the ball 20, creating a circumferential groove at each end of the ball 20. These undercuts 51 and 53 allow the protective coating 40 (as described above) to be applied to an external surface 55 of the ball 20; wrapped around the junctions 50 and 52 of the external surface 55 and the central opening 38 of the ball 20; and attached to the undercuts 51 and 53. Such an arrangement reduces the likelihood of the protective coating 40 peeling away at the junctions 50 and 52, as is problematic with the prior art.

[0030] In the depicted embodiment, shown for example in FIG. 6, the undercuts 51 and 53 each include a longitudinal component 51L and 53L and a transverse component 51T and 53T. As shown, the longitudinal components 51L and 53L extend substantially parallel to the central opening 38 of the ball 20 and extend slightly inward from the central opening 38 forming a slightly larger opening than that of the central opening 38. The transverse components 51T and 53T define the depth of the undercuts 51 and 53. In a preferred embodiment, the depth of the undercuts 51 and 53 is controlled by-the desired thickness of the protective coating 40. This is due to the desirability of having the outer surface of the protective coating 40 flush with the inner surface of the central opening 38. This flush arrangement helps prevent peeling of the protective coating 40 from the undercuts 51 and 53. Merely by way of example, in one embodiment, the depth of the undercuts 51 and 53 and the thickness of the protective coating are each in the range of approximately 0.008 inches to 0.010 inches.

[0031] In addition to these improvements in the durability of the valves of the current invention, the triple valve nature of the current IBOP allows for improved reliability, because it allows for the presence of a secondary or backup mud saver valve. In short, during normal operation when all three valves are in operational condition, only two of the valves are needed for proper operation of the well—the lower IBOP valve 12c, which operates to shut off mud flow, and one of the upper IBOP valves 12a or 12b, which operates as a mud saver. However, because of the high cycle use, the seals of the upper IBOP valve 12a can wear out fairly quickly requiring removal and replacement of the upper IBOP valve, and shut down of the well. The secondary upper IBOP valve 12b of the current invention allows for a backup, such that shut down of the well is not required until both the upper IBOP, or mud saver valves wear out.

[0032] In order to ensure proper operation of the triple valve IBOP of the current invention, in one embodiment each of the upper IBOP valves is supplied with a separate actuator 80a and 80b. As shown in FIG. 8, the actuators for the valves are installed in one embodiment such that a pair of cranks 81 are mounted concentric to the body of a first valve 12a such that the IBOP can close and the valve. These crank in turn can be remotely controlled, such as through a hydraulic or air cylinder in signal communication to a remote controller. Because only one of the two upper IBOP valves needs to be actuated at a time for proper operation of the IBOP, the second upper IBOP valve in such an embodiment is equipped with a mechanical lock 82, such that it cannot be actuated absent being unlocked. Accordingly, when it is necessary to switch to the spare upper IBOP valve the cranks and the mechanical lock are switched and the spare or secondary upper IBOP valve becomes the remotely controllable mud saver valve.

[0033] Although specific embodiments are disclosed herein, it is expected that persons skilled in the art can and will design alternative triple-valve internal blow out preventer systems and methods that are within the scope of the following claims either literally or under the Doctrine of Equivalents.