EP2995768B1

EP2995768B1 - Blowout preventer with blade including multiple profiles

Info

Publication number: EP2995768B1
Application number: EP14306403.8A
Authority: EP
Inventors: Florent Vargas; Pascal Berthaud
Original assignee: Cameron Technologies Ltd
Current assignee: Cameron Technologies Ltd
Priority date: 2014-09-12
Filing date: 2014-09-12
Publication date: 2020-01-22
Anticipated expiration: 2034-09-12
Also published as: WO2016039823A1; US20160258238A1; EP2995768A1

Description

BACKGROUND

This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Blowout preventers (BOPs) are used extensively throughout the oil and gas industry. Typical blowout preventers are used as a large specialized valve or similar mechanical device that seal, control, and monitor oil and gas wells. The two categories of blowout preventers that are most prevalent are ram blowout preventers and annular blowout preventers. Blowout preventer stacks frequently utilize both types, typically with at least one annular blowout preventer stacked above several ram blowout preventers. The ram units in ram blowout preventers allow for both the shearing of the drill pipe and the sealing of the blowout preventer. Typically, a blowout preventer stack may be secured to a wellhead and may provide a safe means for sealing the well in the event of a system failure.
In a typical blowout preventer, a ram bonnet assembly may be bolted to the main body using a number of high tensile bolts or studs. These bolts are required to hold the bonnet in position to enable the sealing arrangements to work effectively. Typically an elastomeric sealing element is used between the ram bonnet and the main body. There are several configurations, but essentially they are all directed to preventing a leakage bypass between the mating faces of the ram bonnet and the main body.
During normal operation, the blowout preventers may be subject to pressures up to 138000 kPa (20,000 psi), or even higher. To be able to operate against and to contain fluids at such pressures, blowout preventers are becoming larger and stronger. Blowout preventer stacks, including related devices, 9.1 meters (30 feet) or more in height are increasingly common.
As noted above, ram-type blowout preventers may be designed and constructed for use with drill pipe or other tubulars of specified diameter. A blowout preventer stack including rams for one size of pipe may be used with pipe of a different size by changing the pipe engaging rams or parts of the rams. Also, the ram operating mechanisms in a blowout preventer are comparatively complex and require inspection and servicing before the blowout preventer is put into service at a wellhead. Such activities, when performed in a large modern blowout preventer stack, may require the presence of personnel at locations that can be hazardous, if not impractical.
Document EP2484860 A2 discloses a pair of shear blades and a blowout preventer having the pair of shear blades. The shear blades are configured to cut a tubular inside the blowout preventer. The shear blades have different geometries of the front cutting surfaces. One geometry promotes a secure positioning of the tubular relative to the first blade while the second geometry promotes a puncturing of the tubular by the second blade.
Document US2007/0246215 A1 discloses methods and apparatuses for severing a wellbore tubular, the apparatus, in certain aspects, including: a first member movable toward a tubular to be severed; a second member with a second blade disposed opposite to the first member and movable toward the tubular; a first blade on the first member having a projection projecting from a center of a blade body with point structure on the projection for puncturing the tubular and cutting surfaces on the projection for cutting the tubular; and cutting surfaces, as needed, on the blade body adjacent the projection for cutting the tubular.
Document US2011/0226477 discloses a method for severing a tubular of a wellbore is provided. The method involves positioning a blowout preventer about a tubular, the blowout preventer having a plurality of rams slidably positionable therein and a plurality of blades carried by the rams for engaging the tubular. The method further involves piercing the tubular with a piercing point of at least one of the blades such that a portion of the tubular is dislodged therefrom, and raking through the tubular with a cutting surface of at least one of the blades.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of the present disclosure, reference will now be made to the accompanying drawings in which:

FIGS. 1A-1C show multiple cross-sectional views of a blowout preventer for shearing a tubular in accordance with one or more embodiments of the present disclosure;
FIGS. 2A-2G show multiple views of a first shear ram and a second shear ram for a blowout preventer to shear a tubular in accordance with the present disclosure;
FIGS. 3A-3G show multiple views of a first shear ram and a second shear ram for a blowout preventer to shear a tubular in accordance with the present disclosure;
FIGS. 4A-4G show multiple views of a first shear ram and a second shear ram for a blowout preventer to shear a tubular in accordance with the present disclosure; and
FIGS. 5A and 5B show multiple perspective views of a first shear ram and a second shear ram for a blowout preventer to shear a tubular in accordance with the present disclosure.

DETAILED DESCRIPTION

The following discussion is directed to various embodiments of the present disclosure. The drawing figures are not necessarily to scale. Certain features of the embodiments may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment.
Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but are the same structure or function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.
In the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to... ." Also, the term "couple" or "couples" is intended to mean either an indirect or direct connection. In addition, the terms "axial" and "axially" generally mean along or parallel to a central axis (e.g., central axis of a body or a port), while the terms "radial" and "radially" generally mean perpendicular to the central axis. For instance, an axial distance refers to a distance measured along or parallel to the central axis, and a radial distance means a distance measured perpendicular to the central axis. The use of "top," "bottom," "above," "below," and variations of these terms is made for convenience, but does not require any particular orientation of the components.
Reference throughout this specification to "one embodiment," "an embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present disclosure. Thus, appearances of the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
Referring now to FIGS. 1A-1C, multiple views of a blowout preventer 10 for shearing a tubular D in accordance with one or more embodiments of the present disclosure are shown. The blowout preventer 10, which may be referred to as a ram blowout preventer, includes a body 12 with a vertical bore 14 formed and/or extending through the body 12. As shown, the body 12 may include a lower flange 16 and/or an upper flange 18, such as to facilitate connecting the blowout preventer 10 to other blowout preventers and/or other components. Cavities and/or guideways 20 and 22 may be formed within the body 12 of the blowout preventer 10, in which the guideways 20 and 22 may extend outwardly from the bore 14 and/or be formed on opposite sides of the bore 14.
The blowout preventer 10 may then include one or more ram assemblies, such as a first ram 24 and a second ram 26. The first ram 24 may be positioned and movable within the first guideway 20 and a second ram 26 positioned and movable within the second guideway 22, such as by having the first ram 24 and/or the second ram 26 movable towards and away from the tubular D. One or more actuators 28 may be provided to move the first ram 24 and/or the second ram 26, such as for moving the first ram 24 and/or the second ram 26 into the bore 14 to shear the portion of the tubular D extending through the bore 14 of the blowout preventer 10. In this embodiment, a hydraulic actuator is shown, though any type of actuator (e.g., pneumatic, electrical, mechanical) may be used in accordance with the present disclosure. As such, the actuators 28 shown in this embodiment may include a piston 30 positioned within a cylinder 32 and a rod 34 connecting the piston 30 to each respective ram 24 and 26. Further, pressurized fluid may be introduced and fluidly communicated on opposite sides of the piston 30 through ports 35, thereby enabling the actuator 28 to move the rams 24 and 26 in response to fluid pressure.
A first (e.g., upper) blade 36 (any blade according to the present disclosure) may be included with or connected to the first ram 24, and a second (e.g., lower) blade 38 (any blade according to the present disclosure) may be included with or connected to the second ram 26. The first and second blades 36 and 38 may be formed and positioned such that a cutting edge of the second blade 38 passes below a cutting edge of the first blade 36 in shearing of a section of a tubular D. The shearing action of first and second blades 36 and 38 may shear the tubular D. The lower portion of the tubular D may then drop into the well bore (not shown) below the blowout preventer 10, or the tubular D may hung off a lower set of rams (not shown).
Accordingly, disclosed herein are a system, blowout preventer, and/or a blade for a blowout preventer for shearing a tubular. The tubular may be positioned within the bore extending through the blowout preventer, in which the blowout preventer may be actuated to move one or more blades to engage and shear the tubular. A blade of a blowout preventer in accordance with the present disclosure may be used for shearing one or more different types of tubulars that may have different shapes, sizes, thicknesses, and other dimensions and properties. For example, a tubular may include a drill pipe joint, a casing joint, and/or a tool joint, in which a blowout preventer in accordance with the present disclosure may be used to shear each of these different types of tubulars. These tubulars may be sheared with or without replacement of any blade of the blowout preventer.
Referring now to FIGS. 2A-2G, multiple views of one or more components for a blowout preventer 200 to shear a tubular in accordance with the present disclosure are shown. A blowout preventer 200 may include a first (e.g., upper) shear ram 202A and a second (e.g., lower) shear ram 202B, in which the first shear ram 202A and/or the second shear ram 202B may be movable towards and/or away a bore of the blowout preventer, such as for shearing a tubular positioned within the bore of the blowout preventer.
Accordingly, FIG. 2A shows an above perspective view of the first shear ram 202A and the second shear ram 202B, and FIG. 2B shows a below perspective view of the first shear ram 202A and the second shear ram 202B. FIG. 2C shows an above view of the first shear ram 202A and the second shear ram 202B fully retracted with a full bore 290. Further, as discussed above, a blowout preventer in accordance with the present disclosure may be used for shearing one or more different tubulars. As such, FIG. 2D shows an above view of the first shear ram 202A and the second shear ram 202B moved towards a casing joint 292A for engaging and shearing the casing joint 292A, FIG. 2E shows an above view of the first shear ram 202A and the second shear ram 202B moved towards a tool joint 292B for engaging and shearing the tool joint 292B, FIG. 2F shows an above view of the first shear ram 202A and the second shear ram 202B moved towards a drill pipe joint 292C for engaging and shearing the drill pipe joint 292C, and FIG. 2G shows an above view of the first shear ram 202A and the second shear ram 202B fully closed, such as after shearing a tubular.
The first shear ram 202A includes a first blade 204A, and the second shear ram 202B includes a second blade 204B. The blades 204A and 204B may be formed integrally with the shear rams 202A and 202B. For example, as shown in FIGS. 5A and 5B, the blades 504A and 504B may be formed integrally with the shear rams 502A and 502B. Alternatively, as shown in FIGS. 2A-2G, the blades 204A and 204B, or at least a portion thereof, may be replaceable with respect to the shear rams 202A and 202B. As such, the first shear ram 202A may include a slot 206A formed therein, in which an insert 208A including the first blade 204A may be inserted into the slot 206A to be removably connected to (e.g., replaceable within) the first shear ram 202A. Further, the second shear ram 202B may include a slot 206B formed therein, in which an insert 208B including the second blade 204B may be inserted into the slot 206B to be removably connected to (e.g., replaceable within) the second shear ram 202B.
A blade in accordance with the present disclosure may include one or more cutting profiles formed thereon or included therewith. As such, the first blade 204A may include an outer cutting profile 210A and an inner cutting profile 212A. The inner cutting profile 212A may be positioned within or between portions of the outer cutting profile 210A. For example, the outer cutting profile 210A may include a first blade portion 214A and a second blade portion 216A, in which the inner cutting profile 212A is positioned between the blade portions 214A and 216A such that the blade portions 214A and 216A are positioned on opposite sides of the inner cutting profile 212A.
Similarly, the second blade 204B may include an outer cutting profile 210B and an inner cutting profile 212B. The inner cutting profile 212B may be positioned within or between portions of the outer cutting profile 210B. For example, the outer cutting profile 210B may include a first (e.g., third overall) blade portion 214B and a second (e.g., fourth overall) blade portion 216B, in which the inner cutting profile 212B is positioned between the blade portions 214B and 216B such that the blade portions 214B and 216B are positioned on opposite sides of the inner cutting profile 212B.
As mentioned above, a blade in accordance with the present disclosure may be used within a shear ram of a blowout preventer, such as to shear one or more different types of tubulars with the blowout preventer. As such, a blade in accordance with the present disclosure may be designed to reduce stress concentrations to facilitate this shearing action. Accordingly, in one embodiment, blade portions of an outer cutting profile may be positioned at least about 120 degrees from each other.
For example, with reference to FIG. 2C, the blade portions 214A and 216A of the outer cutting profile 210A of the first blade 204A may be positioned at least about 120 degrees from each other. More particularly, the blade portions 214A and 216A may be positioned between about 120 degrees and about 140 degrees from each other, if not positioned at about 120 degrees from each other. Similarly, the blade portions 214B and 216B of the outer cutting profile 210B of the second blade 204B may be positioned at least about 120 degrees from each other. More particularly, the blade portions 214B and 216B may be positioned between about 120 degrees and about 140 degrees from each other, if not positioned at about 120 degrees from each other. Such a configuration may enable the outer cutting profiles 210A and 210B of the blades 204A and 204B to have a V-profile.
Further, the inner cutting profile 212A for the first blade 204A and/or the inner cutting profile 212B for the second blade 204B may be sized to reduce stress concentrations, such as when engaging or shearing a tubular having a particular size or strength. For example, as shown in FIG. 2E, the tool joint 292B may have the largest thickness, compared to the casing joint 292A shown in FIG. 2D and the drill pipe joint 292C shown in FIG. 2F. As such, the inner cutting profiles 212A and 212B may be sized to engage and shear the tool joint 292B. In one or more embodiments, as an outer diameter of a standard tool joint may be about 21.6 cm (8.5 inches), a diameter of the inner cutting profiles 212A and 212B may also be about 21.6 cm (8.5 inches). Further, as a tool joint may have other shapes, sizes, and diameters, an inner cutting profile of a blade in accordance with the present disclosure may be formed to complement the outer profile of the tool joint. This may enable substantially all or the entirety of the inner cutting profile of the blade to engage the tool joint, such as to maximize contact with the tool joint for purposes of shearing.
Referring still to FIGS. 2A-2G, the first shear ram 202A may include a mud slot 220A, such as formed on a bottom surface thereof, and the second shear ram 202B may include a mud slot 220B, such as also formed on a bottom surface thereof. The mud slots 220A and 220B may be used to accommodate the flow of mud and fluid around the shear rams 202A and 202B, particularly when the shear rams 202A and 202B have been at least partially moved into the bore 290. Further, the first shear ram 202A may include an actuator slot 222A, such as formed on a surface of the first shear ram 202A opposite the first blade 204A, and the second shear ram 202B may include an actuator slot 222B, such as formed on a surface of the second shear ram 202B opposite the second blade 204B. The actuator slots 222A and 222B may be used to engage with an actuator, such as a rod 34 (shown in FIGS. 1A-1C), to move the shear rams 202A and 202B into and out of the bore 290.
Referring now to FIGS. 3A-3G, multiple views of a first shear ram 302A and a second shear ram 302B for a blowout preventer to shear a tubular in accordance with the present disclosure are shown. In particular, FIGS. 3A and 3B show perspective views of the shear rams 302A and 302B, and FIG. 3C shows an above view of the shear rams 302A and 302B fully retracted from a full bore 390. Further, FIG. 3D shows an above view of the shear rams 302A and 302B moved towards a casing joint 392A for engaging and shearing the casing joint 392A, FIG. 3E shows an above view of the shear rams 302A and 302B moved towards a tool joint 392B for engaging and shearing the tool joint 392B, FIG. 3F shows an above view of the shear rams 302A and 302B moved towards a drill pipe joint 392C for engaging and shearing the drill pipe joint 392C, and FIG. 3G shows an above view of the shear rams 302A and 302B fully closed, such as after shearing a tubular.
As with the above, the first shear ram 302A includes a first blade 304A, in which, in this embodiment, an insert 308A including the first blade 304A may be inserted into the slot 306A to be removably connected to (e.g., replaceable within) the first shear ram 302A. Similarly, the second shear ram 302B includes a second blade 304B, in which an insert 308B including the second blade 304B may be inserted into the slot 306B to be removably connected to (e.g., replaceable within) the second shear ram 302B.
The first blade 304A may include an outer cutting profile 310A and an inner cutting profile 312A, in which the outer cutting profile 310A may include a first blade portion 314A and a second blade portion 316A and be similar to an outer cutting profile described above. Further, the second blade 304B may include an outer cutting profile 310B and an inner cutting profile 312B, in which the outer cutting profile 310B may include a first blade portion 314B and a second blade portion 316B and be similar to an outer cutting profile described above.
In one or more embodiments, an inner cutting profile in accordance with the present disclosure may be sized and/or shaped to reduce stress concentrations on the blades and/or increase the stress on the tubular when shearing. For example, an inner cutting profile in accordance with the present disclosure may include one or more projections, such as to define one or more initial contact points between a blade and a tubular as the blade moves towards the tubular for shearing. In particular, this may define an initial contact point for the inner cutting profile and/or the blade altogether when contacting and engaging the tubular as a shear ram closes and a blade moves towards the tubular for shearing.
Accordingly, with reference particularly to FIG. 3C, the inner cutting profile 312A of the first blade 304A may include a first projection 324A and a second projection 326A, in which the first projection 324A and/or the second projection 326A may be used to define an initial contact point between the first blade 304A and a tubular (depending on the size and shape of the tubular, as shown in FIGS. 3D-3G). Similarly, the inner cutting profile 312B of the second blade 304B may include a first (e.g., third) projection 324B and a second (e.g., fourth) projection 326B, in which the first projection 324B and/or the second projection 326B may be used to define an initial contact point between the second blade 304B and a tubular. Such a configuration may enable the inner cutting profiles 310A and 310B of the blades 304A and 304B to have a dual indenter-profile. As such, a dual indenter-profile of a blade in accordance with the present disclosure may facilitate centralizing and/or stabilizing a tubular member, independent of size (e.g., a tool joint, a drill pipe joint, and/or a casing joint), when also shearing the tubular member with the blade.
In one or more embodiments, one or more of the projections of the blades of the shear rams may include a radiused edge, such as to reduce stress concentrations at the projection. For example, as shown in FIGS. 3A-3G, each of the projections 324A, 324B, 326A, and 326B may include a radiused edge, in which the projections 324A, 324B, 326A, and 326B may be rounded at an end thereof, such as to prevent damage to the blades 304A and 304B.
Referring now to FIGS. 4A-4G, multiple views of a first shear ram 402A and a second shear ram 402B for a blowout preventer to shear a tubular in accordance with the present disclosure are shown. In particular, FIGS. 4A and 4B show perspective views of the shear rams 402A and 402B, and FIG. 4C shows an above view of the shear rams 402A and 402B fully retracted from a full bore 490. Further, FIG. 4D shows an above view of the shear rams 402A and 402B moved towards a casing joint 492A for engaging and shearing the casing joint 492A, FIG. 4E shows an above view of the shear rams 402A and 402B moved towards a tool joint 492B for engaging and shearing the tool joint 492B, FIG. 4F shows an above view of the shear rams 402A and 402B moved towards a drill pipe joint 492C for engaging and shearing the drill pipe joint 492C, and FIG. 4G shows an above view of the shear rams 402A and 402B fully closed, such as after shearing a tubular.
As with the above, the first shear ram 402A includes a first blade 404A, in which, in this embodiment, an insert 408A including the first blade 404A may be inserted into the slot 406A to be removably connected to (e.g., replaceable within) the first shear ram 402A. Similarly, the second shear ram 402B includes a second blade 404B, in which an insert 408B including the second blade 404B may be inserted into the slot 406B to be removably connected to (e.g., replaceable within) the second shear ram 402B.
The first blade 404A may include an outer cutting profile 410A and an inner cutting profile 412A, in which the outer cutting profile 410A may include a first blade portion 414A and a second blade portion 416A and be similar to an outer cutting profile described above. Further, the second blade 404B may include an outer cutting profile 410B and an inner cutting profile 412B, in which the outer cutting profile 410B may include a first blade portion 414B and a second blade portion 416B and be similar to an outer cutting profile described above.
As discussed above, an inner cutting profile in accordance with the present disclosure may include one or more projections. Accordingly, with reference particularly to FIG. 4C, the inner cutting profile 412A of the first blade 404A may include a first projection 424A, a second projection 426A, and a third projection 428A. The first projection 424A, the second projection 426A, and/or the third projection 428A may be used to define an initial contact point between the first blade 404A and a tubular (depending on the size and shape of the tubular, as shown in FIGS. 4D-4G). Similarly, the inner cutting profile 412B of the second blade 404B may include a first (e.g., fourth) projection 424B, a second (e.g., fifth) projection 426B, and a third (e.g., sixth) projection 428B. The first projection 424B, the second projection 426B, and/or the third projection 428B may be used to define an initial contact point between the second blade 404B and a tubular. Such a configuration may enable the inner cutting profiles 410A and 410B of the blades 404A and 404B to have a triple indenter-profile. As such, a triple indenter-profile of a blade in accordance with the present disclosure may facilitate centralizing and/or stabilizing a tubular member, independent of size (e.g., a tool joint, a drill pipe joint, and/or a casing joint), when also shearing the tubular member with the blade.
In an embodiment in which an inner cutting profile of a blade may include more than two projections, the projections (e.g., edges, tips, and/or contact points of the projections) may be positioned on a radius, diameter, and/or an arc with respect to each other. For example, as an outer diameter of a standard tool joint may be about 21.6 cm (8.5 in), a diameter for the positions of the tips of the projections 424A, 426A, and 428A of the first blade 404A and/or for the positions of the tips of the projections 424B, 426B, and 428B of the second blade 404B may also be about 21.6 cm (8.5 in). This may enable the blades 404A to be able to define similar initial contact points between the projections 424A, 424B, 426A, 426B, 428A, and 428B and a tubular having a similar diameter when shearing the tubular. Those having ordinary skill in the art will appreciate that other sizes, configurations, and diameters may be used for an inner cutting profile, in addition to an outer cutting profile, without departing from the scope of the present disclosure.
As shown in the above embodiments, a blade in accordance with the present disclosure may be symmetrical. For example, with reference to any or all of the blade profiles and configurations discussed above, a line of symmetry may extend through an inner cutting profile of a blade. Further, though the above embodiments show profiles matching between each of the first blades and the second blades, the present disclosure is not so limited. For example, rather than having the first blade match the second blade, other blades or blade profiles may be used with a blade or blade profile identified above within one or more embodiments. Further, the first blade may or may not be identical to the second blade, such as depending on the application.
As discussed above, a blade and a blowout preventer in accordance with the present disclosure may be used to shear one or more tubulars, including a casing joint, a drill pipe joint, and a tool joint, with each having various shapes, sizes, and/or other dimensions. A casing joint may have one or more sizes, such as an outer diameter of about 40.6 cm (16 in), about 35.6 cm (14 in, about 30.5 cm (12 in), and/or about 26.99cm (10.625 in) Further, a drill pipe joint may have one or more sizes, such as an outer diameter of about 16.83cm (6.625 in), about 14.0 cm (5.5 in), and/or about 8.9 cm (3.5 in). As such, one or more blades, shear rams, and/or blowout preventers in accordance with the present disclosure may be used to shear one or more different tubulars and/or different sizes or dimensions of tubulars.
Further, in one or more embodiments, as a blade in accordance with the present disclosure may be replaceable, one or more blades of a blowout preventer may be replaced based upon the tubular. For example, if the blowout preventer is used to shear a tool joint, one or both blades of the blowout preventer may be replaced to have an inner cutting profile (with or without projections) with a diameter similar to that of the tool joint. Replacement may involve replacing the blade only, as an insert may include the blade, or may involve replacing at least a portion of the blade or replacing the shear ram that includes the blade.
While the aspects of the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. But it should be understood that the invention is not intended to be limited to the particular forms disclosed and the scope thereof is set out in the appended claims.

Claims

A blowout preventer (200) for shearing a tubular positioned in a bore extending through the blowout preventer (200), the blowout preventer (200) comprising:
a first shear ram (202A) movable towards the tubular, the first shear ram (202A) comprising a first blade (204A), the first blade (204A) comprising a first outer cutting profile (210A) formed from first and second outer blade portions (214A;216A) and a first inner cutting profile (212A); and

a second shear ram (202B) positioned opposite the first shear ram (202A) with respect to the tubular and movable towards the tubular, the second shear ram (202B) comprising a second blade (204B), the second blade (204B) comprising a second outer cutting profile (210B) formed from third and fourth outer blade portions (214B;216B) and a second inner cutting profile (212B);

wherein for each of the first and second blade (204A;204B), the outer blade portions of the outer cutting profile are positioned on opposite sides of the inner cutting profile (212A) and
characterised in that
the outer blade portions are
positioned between an angle of about 120 degrees and an angle of about 140 degrees from each other; and

wherein a diameter of the inner cutting profiles (212A, 212B) is similar to that of a tool joint of the tubular.
The blowout preventer of claim 1, further comprising:
a first insert (208A) removably connectable to the first shear ram (202A);

wherein the first insert (208A) comprises at least a portion of the first blade (204A).
The blowout preventer of claim 1 or 2, wherein the first blade portion (214A) and the second blade portion (214A;216A) of the outer cutting profiles (210A;210B) are positioned at an angle of about 120 degrees from each other.
The blowout preventer of any of the preceding claims , wherein the outer cutting profiles (210A;210B) comprise a V-profile.
The blowout preventer of any preceding claim, wherein the inner cutting profile (212A;212B) has a diameter of about 21.6 cm (8.5 inches).
The blowout preventer of claim 1, wherein the inner cutting profiles (212A;212B) each comprise at least one projection (324A;324B) to define an initial contact point of the first and second blades (204A;204B) with the tubular when the first and second shear rams move towards the tubular.
The blowout preventer of claim 6, wherein the inner cutting profile comprises a first projection (424A) and a second projection (426A) such that at least one of the first projection and the second projection defines the initial contact point of the first and second blades with the tubular.
The blowout preventer of claim 7, wherein the inner cutting profile further comprises a third projection (428A), and wherein tips of the first projection, the second projection, and the third projection are positioned on the diameter of the inner profile with respect to each other.
The blowout preventer of any preceding claim, wherein the first and second blades (204A;204B) are symmetrical such that a line of symmetry extends through the inner cutting profile (212A) of the first blade (204A).
The blowout preventer of any preceding claim, wherein the tubular further comprises a plurality of tubulars comprising a drill pipe joint, a casing joint, and a tool joint such that the blowout preventer (200) is configured to shear each of the drill pipe joint, the casing joint, and the tool joint.
A method for operating a blowout preventer to shear a tubular within the blowout preventer, comprising:
moving a first blade (204A) comprising a first outer cutting profile (210A) and a first inner cutting profile (212A) toward the tubular, the first outer cutting profile (210A) comprising a first blade portion (214A) and a second blade portion (216A), each on opposite sides of the first inner cutting profile (212A) and positioned between an angle of about 120 degrees and an angle of about 140 degrees from each other, wherein the first inner cutting profiles (212A) comprises at least two projections (324A;324B) with rounded ends to define initial contact points of the first blade (204A) with the tubular;

moving a second blade (204B) comprising a second outer cutting profile (210B) and a second inner cutting profile (212B) toward the tubular within the blowout preventer, the second outer cutting (210B) profile comprising a third blade portion (214B) and a fourth blade portion (216B), each on opposite sides of the second inner cutting profile (212B), and positioned between an angle of about 120 degrees and an angle of about 140 degrees from each other, wherein a diameter of the inner cutting profiles (212A, 212B) is similar to that of a tool joint of the tubular; and

shearing the tubular with the first blade and the second blade (204B).
The method of claim 11, wherein the tubular further comprises a plurality of tubulars comprising a drill pipe joint, a casing joint, and a tool joint, wherein the shearing the tubular comprises at least one of:
shearing the drill pipe joint by moving the first blade and the second blade towards the drill pipe joint;

shearing the casing joint by moving the first blade and the second blade towards the casing joint; and

shearing the tool joint by moving the first blade and the second blade towards the tool joint.