PRESSURE CONTAINMENT DEVICES

Abstract

A pressure containment device includes a sealing element. The sealing element includes a longitudinal axis, a substantially annular cross-section arranged perpendicular to the longitudinal axis, a radially inwardly facing interior surface having a plurality of recesses, a radially outwardly facing exterior surface, a first end surface having a plurality of recesses, and a second end surface. The first end surface and the second end surface are each arranged to extend from the radially inwardly facing interior surface to the radially outwardly facing exterior surface. The first end surface and the second end surface are arranged at opposite ends of the sealing element.

Claims

22: A pressure containment device comprising: a sealing element comprising: a longitudinal axis; a cross-section arranged perpendicular to the longitudinal axis, the cross-section being configured to be substantially annular; a radially inwardly facing interior surface comprising a plurality of recesses; a radially outwardly facing exterior surface; a first end surface comprising a plurality of recesses; and a second end surface, wherein, the first end surface and the second end surface are each arranged to extend from the radially inwardly facing interior surface to the radially outwardly facing exterior surface, and the first end surface and the second end surface are arranged at opposite ends of the sealing element.

23: The pressure containment device as recited in claim 22, wherein the recesses of the radially inwardly facing interior surface are arranged to form a first set of recesses in which the recesses are spaced around a circumference of the radially inwardly facing interior surface.

24: The pressure containment device as recited in claim 23, wherein the recesses of the first set of recesses are arranged exclusively in the radially inwardly facing interior surface between the first end surface and the second end surface.

25: The pressure containment device as recited in claim 24, wherein the recesses of the first set of recesses are arranged substantially centrally between the first end surface and the second end surface.

26: The pressure containment device as recited in claim 25, wherein the recesses of the first set of recesses are arranged so as to be regularly spaced around the circumference of the radially inwardly facing interior surface.

27: The pressure containment device as recited in claim 22, wherein the recesses of the first end surface are arranged to form a second set of recesses in which the recesses are spaced in an array which is substantially circular.

28: The pressure containment device as recited in claim 27, wherein the recesses of the second set of recesses are arranged so as to be regularly spaced in the array.

29: The pressure containment device as recited in claim 22, wherein, each of the recesses comprises a center, the center of each of the recesses is arranged on a respective imaginary plane in which the longitudinal axis of the sealing element is also arranged, and the imaginary plane associated with each recess in the second set of recesses is located directly between two of the imaginary planes associated with recesses of the first set of recesses.

30: The pressure containment device as recited in claim 29, wherein the imaginary plane associated with each recess in the second set of recesses is located centrally between two of the imaginary planes associated with recesses of the first set of recesses.

31: The pressure containment device as recited in claim 29, wherein an angle between adjacent imaginary planes is substantially equal for all pairs of adjacent imaginary planes.

32: The pressure containment device as recited in claim 22, wherein, each of the recesses comprises a center, the center of each of the recesses is arranged on a respective imaginary plane in which the longitudinal axis of the sealing element is also arranged, and the imaginary plane associated with each recess in the first set of recesses is located directly between two of the imaginary planes associated with the recesses of the second set of recesses.

33: The pressure containment device as recited in claim 32, wherein the imaginary plane associated with each recess in the first set of recesses is located centrally between two of the imaginary planes associated with the recesses of the second set of recesses.

34: The pressure containment device as recited in claim 32, wherein an angle between adjacent imaginary planes is substantially equal for all pairs of adjacent imaginary planes.

35: The pressure containment device as recited in claim 22, further comprising: an actuator assembly which is configured to engage with the sealing element so as to reduce a diameter of a space enclosed by the radially inwardly facing interior surface.

36: The pressure containment device as recited in claim 35, further comprising: a housing, wherein, the actuator assembly is further configured to push the sealing element against the housing so as to reduce the diameter of the space enclosed by the radially inwardly facing interior surface.

37: The pressure containment device as recited in claim 35, wherein the actuator assembly comprises a piston which is configured to be moved by a supply of a pressurized fluid to the pressure containment device.

38: The pressure containment device as recited in claim 37, wherein the piston is configured to be moved substantially parallel to the longitudinal axis of the pressure containment device by the supply of the pressurized fluid to the pressure containment device.

39: The pressure containment device as recited in claim 22, wherein the sealing element is predominantly made from an elastomer.

40: The pressure containment device as recited in claim 22, wherein the sealing element further includes a plurality of rigid inserts.

41: The pressure containment device as recited in claim 40, wherein the plurality of rigid inserts are arranged so as to be spaced apart from one another in an array which is substantially circular around a space enclosed by the radially inwardly facing interior surface of the sealing element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:

[0014] FIG. 1 is a schematic illustration of a transverse cross-section through a conventional, prior art, elastomeric sealing element 10′ of the type used in conventional, prior art, blowout preventers a) in a relaxed state and b) in a compressed state;

[0015] FIG. 2 is an illustration of a longitudinal cross section through a pressure containment device according to the present invention;

[0016] FIG. 3 is an isometric view of the longitudinal cross section through a pressure containment device illustrated in FIG. 2;

[0017] FIG. 4 is an isometric view of the longitudinal cross section through a pressure containment device illustrated in FIG. 2 with a portion of a drill string extending through the pressure containment device;

[0018] FIG. 5 is an illustration of a longitudinal cross-section through the sealing element of the pressure containment device illustrated in FIGS. 2 and 3;

[0019] FIG. 6 is an isometric view of the longitudinal cross-section through the sealing element illustrated in FIG. 5;

[0020] FIG. 7 is a schematic illustration of a transverse cross-section through the sealing element illustrated in FIGS. 5 and 6 a) in a relaxed state and b) in a compressed state;

[0021] FIG. 8 is an illustration of a longitudinal cross-section through an embodiment of sealing element;

[0022] FIG. 9 is an isometric view of the longitudinal cross-section through the sealing element illustrated in FIG. 8;

[0023] FIG. 10 is an illustration of a longitudinal cross-section through an embodiment of the sealing element; and

[0024] FIG. 11 is an isometric view of the longitudinal cross-section through the sealing element illustrated in FIG. 10.

DETAILED DESCRIPTION

[0025] The present invention provides a pressure containment device comprising a sealing element having a longitudinal axis and a cross-section perpendicular to its longitudinal axis which is generally annular, the sealing element thus having a radially inwardly facing interior surface, a radially outwardly facing exterior surface, and a first end surface and a second end surface which extend from the interior surface to the exterior surface, wherein both the interior surface and the first end surface are provided with a plurality of discrete recesses.

[0026] The recesses provided in the interior surface form a first set of recesses in which the recesses are spaced around the circumference of the interior surface. In one embodiment, the recesses in the first set can, for example, be located exclusively in the interior surface between the first end surface and the second end surface. In this case, the recesses in the first set may be located generally centrally between the first end surface and the second end surface. In one embodiment, the recesses in the first set can, for example, be regularly spaced around the circumference of the interior surface.

[0027] The recesses provided in the end surface form a second set of recesses in which the recesses are spaced in a generally circular array. In one embodiment, the recesses in the second set can, for example, be regularly spaced in a generally circular array.

[0028] In one embodiment, a center of each of the recesses can, for example, be located on an imaginary plane in which the longitudinal axis of the sealing element also lies, and the imaginary plane associated with each recess in the second set is located directly between two of the imaginary planes associated with recesses of the first set. In one embodiment, the imaginary plane associated with each recess in the first set can, for example, be located directly between two of the imaginary planes associated with the recesses of the second set.

[0029] The imaginary plane associated with each recess in the second set may be located centrally between two of the imaginary planes associated with recesses of the first set.

[0030] The imaginary plane associated with each recess in the first set may be located centrally between two of the imaginary planes associated with the recesses of the second set.

[0031] In one embodiment, the angle between adjacent imaginary planes can, for example, be substantially equal for all pairs of adjacent imaginary planes.

[0032] The pressure containment device may further comprise an actuator assembly which is operable to engage with the sealing element to reduce the diameter of the space enclosed by the interior surface.

[0033] The pressure containment device may further include a housing, the actuator assembly being operable to push the sealing element against the housing to reduce the diameter of the space enclosed by the interior surface.

[0034] The actuator assembly may comprise a piston movable by the supply of pressurized fluid to the pressure containment device. In one embodiment, the piston can, for example, be movable generally parallel to a longitudinal axis of the pressure containment device by the supply of pressurized fluid to the pressure containment device.

[0035] The sealing element may be made predominantly from an elastomer.

[0036] The sealing element may include a plurality of rigid inserts. In this case, the inserts may be metallic. The inserts may be spaced from one another and arranged in a generally circular array around the space enclosed by the interior surface of the sealing element.

[0037] Embodiments of the present invention will now be described with reference to the accompanying drawings.

[0038] Referring now to FIGS. 2 and 3, there is shown a blowout preventer 14 having a housing 16 in which is located a sealing element 10 and an actuator assembly 18. The sealing element 10 has a longitudinal axis A and a cross-section perpendicular to its longitudinal axis A which is generally annular. The sealing element 10 thus has a radially inwardly facing interior surface 10a, a radially outwardly facing exterior surface 10b, and a first end surface 10c and a second end surface 10d which extend from the radially inwardly facing interior surface 10a to the radially outwardly facing exterior surface 10b, at opposite ends of the sealing element 10. Both the radially inwardly facing interior surface 10a and the first end surface 10c are provided with a plurality of discrete recesses 20.

[0039] In this example, the end surfaces 10c, 10d of the sealing element 10 extend generally perpendicular to the radially inwardly facing interior surface 10a.

[0040] The actuator assembly 18 is operable to engage with the sealing element 10 to reduce the diameter of the space enclosed by its radially inwardly facing interior surface 10a.

[0041] In one embodiment, the actuator assembly 18 is operable to push the sealing element 10 against the housing 16 to reduce the diameter of the space enclosed by the radially inwardly facing interior surface 10a.

[0042] In the example illustrated in FIGS. 2 and 3, the actuator assembly 18 comprises a piston movable by the supply of pressurized fluid to the pressure containment device. In this embodiment, the piston is movable generally parallel to a longitudinal axis A by the supply of pressurized fluid to an activation chamber provided in the housing 16 of the pressure containment device.

[0043] In one embodiment, the housing 16 is provided in two parts 16a, 16b, the first part 16a having a curved interior surface which is intended to engage with the sealing element 10 and to cause the sealing element 10 to constrict when the sealing element 10 is pushed against the housing 16 by the actuator assembly 18.

[0044] It should be appreciated, however, that the present invention is not restricted to this type of actuator assembly 18. The actuator assembly may, for example, comprise a ram/piston or plurality of rams/pistons which is/are movable perpendicular to the longitudinal axis A and radially inwardly of the sealing element 10. Alternatively, the actuator assembly 18 may comprise a supply of pressurized fluid and means to direct the pressurized fluid to act directly on the radially outwardly facing exterior surface 10b of the sealing element 10 to compress the sealing element 10 and thus reduce the diameter of the space enclosed by the radially inwardly facing interior surface 10a.

[0045] FIG. 4 shows a tubular drill string 12 extending through the blowout preventer 14. In this example, the tubular drill string 12 extends along the longitudinal axis A of the sealing element 10.

[0046] The sealing element 10 is illustrated in more detail in FIGS. 5 and 6.

[0047] The recesses 20 provided in the radially inwardly facing interior surface 10a form a first set of recesses 20a in which the recesses 20 are located exclusively in the radially inwardly facing interior surface 10a between the first end surface 10c and the second end surface 10d, spaced around the circumference of the radially inwardly facing interior surface 10a. In this example, the recesses in the first set of recesses 20a are located generally centrally between the first end surface 10c and the second end surface 10d, and are regularly spaced around the circumference of the radially inwardly facing interior surface 10a.

[0048] The recesses 20 provided in the end surface 10c form a second set of recesses 20b in which the recesses 20 are spaced in a generally circular array. In this example, the recesses 20 in the second set of recesses 20b are regularly spaced in a generally circular array.

[0049] In this example, each set of recesses 20a, 20b has 6 recesses 20.

[0050] In this example, the recesses 20 in the second set of recesses 20b are located at the interface between the end surface 10c and the radially inwardly facing interior surface 10a.

[0051] The center of each of the recesses 20 is located on an imaginary plane in which the longitudinal axis A of the sealing element 10 also lies, and in this example, the imaginary plane associated with each recess 20 in the first set of recesses 20a is located directly between two of the imaginary planes associated with recesses 20 of the second set of recesses 20b, whilst the imaginary plane associated with each recess 20 in the second set of recesses 20b is located directly between two of the imaginary planes associated with the recesses 20 of the first set of recesses 20a In other words, when viewed from a direction generally parallel to the longitudinal axis A, each recess 20 in the first set of recesses 20a is located between two recesses 20 from the second set of recesses 20b and vice versa.

[0052] In this case, the angle between adjacent imaginary planes is substantially equal for all pairs of adjacent imaginary planes.

[0053] The sealing element 10 may be made predominantly from an elastomer such as hydrogenated nitrile butadiene rubber (HNBR), nitrile rubber (NBR), polyurethanes or a combination thereof. Rubbers and elastomers having a durometer range between 50 Shore A and 100 Shore A may be used. Composite materials which include elastomers, polymers and fiber-reinforced elastomers or fluorocarbons may also be used. The elastomeric material may further be modified by the addition of friction reducers.

[0054] In this example, the sealing element includes a plurality of rigid inserts 22. These can, for example, be metallic.

[0055] In this example, the rigid inserts 22 are regularly spaced from one another and arranged in a generally circular array around the space enclosed by the radially inwardly facing interior surface 10a of the sealing element 10.

[0056] A transverse cross-section (in a plane perpendicular to the longitudinal axis A) through the sealing element 10 and associated tubular drill string 12 is illustrated schematically in FIGS. 7a and 7b. FIG. 7a shows the sealing element 10 in its undeformed, relaxed, state in which the radially inwardly facing interior surface 10a of the sealing element 10 is spaced from the tubular drill string 12. FIG. 7b shows the sealing element 10 in its deformed state in which the actuator assembly 18 has acted on the sealing element 10 to cause it to constrict about the tubular drill string 12.

[0057] As mentioned earlier in relation to prior art blowout preventers, the deformation/folding pattern on the elastomeric material on the sealing element 10 depends on either the buckling modes or the defects/weak regions of the elastomer ring. The recesses 20 at the inner surface regions provide the least resistance for material folding, and hence the material will fold at each recess 20. As a result, the folding pattern will be more regular at the inner surface of the elastomer as shown in FIG. 7b. These regular folds create the same level of strain in all the folds. This may increase the life of the elastomeric component of the sealing element 10 due to the reduction in the available strain energy density at the critical folding regions. This regular folding pattern distributes the sealing surface evenly around the circumference of the tubular drill string 12, and the radial compressive force required to seal around the tubular drill string 12 may be reduced.

[0058] The exact shape of the recesses 20 may be varied. Alternative embodiments of sealing elements 10 are illustrated in FIGS. 8, 9, 10 and 11. In the example illustrated in FIGS. 8 and 9, the recesses 20 are generally elliptical with the recesses 20 in the first set of recesses 20a have the shape of roughly half of an ellipsoid (cut longitudinally), whilst the recesses 20 in the second set of recesses 20b have the shape of roughly one quarter of an ellipsoid. In the example illustrated in FIGS. 10 and 11, the recesses 20 in the first set 20a of recesses have the shape of a longitudinal cross-section through a cylinder, whilst the recesses 20 in the second set of recesses 20b have the shape of a portion of an ovoid. The recesses 20 in the second set of recesses 20b could, of course, have the shape of a quarter of a cylinder.

[0059] Whilst in the examples described above, it is specified that recesses 20 are provided only the radially inwardly facing interior surface 10a and the radially outwardly facing end surface 10b of the sealing element 10, it should be appreciated that the sealing element 10 has a second end surface 10d which also extends between the radially inwardly facing interior surface 10a and the radially outwardly facing exterior surface 10b at an opposite end of the sealing element 10 to the first end surface 10c. A third set of recesses 20c may also be provided in this second end surface 10d as illustrated in FIGS. 8 and 9. In this example, the recesses 20 in the second set of recesses 20b and the third set of recesses 20c are arranged such that on each imaginary plane (containing the longitudinal axis A) associated with a recess 20 in either of the end surfaces 10c, 10d there is either a recess 20 in the second set of recesses 20b or a recess 20 in the third set of recesses 20c, not both. Also in this example, the recesses 20 in the second set of recesses 20b and the third set of recesses 20c alternate moving around the longitudinal axis A of the sealing element 10. It should be appreciated, however, that this need not be the case, and recesses 20 in both the second set of recesses 20b and the third set of recesses 20c may be provided in the same imaginary plane.

[0060] The exact location, number, size, pattern of distribution (regular/irregular), number of sets in each surface and shape of the recesses 20 may, of course, be varied to achieve a desired folding pattern. The exact location, number, size and shape of the recesses 20 required will depend on the mechanical properties of the elastomeric material from which the sealing element 10 is made, the absence/presence of rigid inserts 22 and their number, the dimensions of the sealing element 10, the actuation mechanism, and the degree of constriction required.

[0061] At least 3 recesses can, for example, be provided in each set.

[0062] When used in this specification and claims, the terms “comprises” and “comprising” and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

[0063] The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilized for realizing the present invention in diverse forms thereof. The present invention is not limited to embodiments described herein; reference should be had to the appended claims.