Patent Application
20170067308
Embodiments of the present disclosure relate generally to blowout preventers, and more specifically, to an improved lateral seal for shear blocks in a blowout preventer ram unit.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. 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 disclosure. Accordingly, it should be understood that these statements are to be read in this light and not as admissions of prior art.
Blowout preventers are used extensively throughout the oil and gas industry. Typical blowout preventers include a main body to which are attached various types of ram units. 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 wellbore tubular and the sealing of the blowout preventer. Typically, a blowout preventer stack may be secured to a wellhead and may provide a means for sealing the well in the event of a system failure.
Existing ram units often include shear blocks or shear blades designed to be forced together to shear the wellbore tubular and seal the blowout preventer. The shear blocks generally feature opposing blade profiles used to cut the wellbore tubular. It is desirable to provide an effective seal between the opposing shear blocks to help seal the blowout preventer.
For a more complete understanding of the present disclosure and its features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:
One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
Generally, embodiments of the disclosure are directed to a blowout preventer having a ram unit designed to shear and seal wellbore tubulars. The ram unit may include a first shear blade and a second shear blade designed to be moved towards each other to shear a wellbore tubular. The presently disclosed embodiments are directed to a lateral seal assembly that may be used to generate a seal between the shear blades after they are closed to shear the tubular. The seal assembly may be disposed on the second shear blade. The seal assembly may include at least a wiper, a sealing element, and an energizer packaged as a single seal assembly. The wiper may include a hard component for cleaning a surface of the first shear blade as the blade moves relative to the second shear blade. The sealing element may include an elastomeric material that may be deformed into a sealing engagement with the first shear blade to generate the seal. The energizer may be a hard component that energizes the sealing element against the cleaned surface of the first shear blade as the blade moves further relative to the second shear blade.
The wiper is used to clean the sealing surface of the shear blade by removing oil, cuttings, and debris from the surface prior to the energizer activating the seal, thus enabling a more secure seal to be established on the blade surface. Therefore, the disclosed system and method may provide effective sealing of the shear blades and any tubulars disposed therein.
Turning now to the drawings,
As illustrated, the shear blades 12 and 14 may be vertically offset from one another, as shown in
In the illustrated embodiments, each of the shear blades 12 and 14 may include a specific blade profile designed to shear the wellbore tubular 16 in an efficient manner. For example, the blade profiles may include concave cutouts toward the center of the shear blade profiles, as shown. In some embodiments, the blade profiles for the opposing shear blades 12 and 14 may be different from one another. However, it should be noted that in other embodiments the shear blades 12 and 14 may each feature the same blade profile, or any desired combination of blade profiles.
As shown, the seal assembly 30 may be disposed on just one of the shear blades of the ram unit 10. For example, in the illustrated embodiment the seal assembly 30 is generally disposed on a lower side 32 of the upper shear blade 14 and designed to interface with an upper side 34 of the lower shear blade 12 when the shear blades 12 and 14 are brought together. In other embodiments, the seal assembly 30 may be disposed on the upper face 34 of the lower shear blade 12 to interface with the lower surface 32 of the upper shear blade 14.
In still other embodiments, each of the blades 12 and 14 may be equipped with their own seal assembly 30 for interfacing with the opposing blades 14 and 12. In such instances, it may be desirable for the seal assemblies 30 to be positioned on the shear blades 12 and 14 such that, when the shear blades 12 and 14 are brought together to shear and seal the wellbore tubular, the activated seal assemblies 30 are laterally offset from one another. This may enable each of the seal assemblies 30 to interface directly with an opposing shear blade surface.
All of the functions provided by the seal assembly 30 may be performed in response to the shear blades 12 and 14 being brought together by the ram unit. It should be noted that this movement of the shear blades 12 and 14 may be brought on by the ram unit physically moving just the shear blade 12 toward a stationary shear blade 14, just the shear blade 14 toward a stationary shear blade 12, or both of the shear blades 12 and 14 toward each other. In each instance, the net movement of the shear blades 12 and 14 may be represented as the shear blade 12 moving laterally in the direction of arrow 56 with respect to the shear blade 14 having the seal assembly 30. This lateral movement 56 of the shear blade 12 may initiate and facilitate the cleaning/sealing functions of the seal assembly 30, as described in detail below.
In
Once the shear blade 12 laterally overlaps the shear blade 14, the system may begin clearing debris from a sealing surface 58 of the shear blade 12. The sealing surface 58 is a surface of the shear blade 12 that the seal assembly 30 may clean and then engage with the sealing element 52 to form the seal. As shown, relatively large debris 60 may be removed from the sealing surface 58 via the overlapping shear blades 12 and 14. The debris 60 may be so large that it cannot fit through a space 62 between the overlapping shear blades 12 and 14. As the shear blade 12 moves relative to the shear blade 14 in the direction of arrow 56, the large debris 60 on the sealing surface 58 may become caught on a surface 64 of the shear blade 14. This surface 64 may slope substantially upward from the lateral direction 56 of movement of the shear blade 12, which helps to trap the debris 60 in a space between the two shear blades 12 and 14.
Although the shear blades 12 and 14 themselves may be effective at cleaning large debris 60 from the sealing surface 58, additional small debris, cuttings, and oil may remain on the sealing surface 58 after this initial pass by the shear blade 14. As shown in
As the shear blade 12 moves relative to the seal assembly 30, the wiper 50 may engage and clean the sealing surface 58 of the shear blade 12, as illustrated in
As shown, the wiper 50 may include a relatively flat lower surface for engaging and cleaning the sealing surface 58 of the shear blade 12. In addition, the wiper 50 may include a sloped surface 70 formed on an end of the wiper 50 extending toward the shear blade 12. The sloped surface 70 may help to define a relatively small pocket 72 between the shear blade 14, the shear blade 12, and the wiper 50. This pocket 72 may collect the debris, cuttings, and/or oil that is removed from the sealing surface 58 via the wiper 50. If the pocket 72 fills with debris, any additional debris removed via the wiper 50 may be pushed into the small space 62 between the two shear blades 12 and 14.
As the shear blade 12 moves laterally (e.g., arrow 56) along the seal assembly 30, the shear blade 12 may contact the wiper 50 and force the wiper 50 in a direction (e.g., upward) away from the shear blade 12, as shown by arrow 74. The sloped surface 70 of the wiper 50 may facilitate this transition from the lateral force of the shear blade 12 against the wiper 50 to the vertical movement 74 of the wiper 50. A portion 76 of the sealing element 52 may be disposed between an end of the wiper 50 (opposite the sloped surface end) and the shear blade 14. This portion 76 of the sealing element 52 may cushion the vertical movement of the wiper 50 as the shear blade 12 moves past the wiper 50. In addition, the portion 76 of the sealing element 52 may be relatively resistant to movement, thereby biasing the wiper 50 toward the shear blade 12. That way, as the shear blade 12 moves laterally past the wiper 50, the wiper 50 may be biased toward the shear blade 12 to continuously clean the sealing surface 58.
Again, as the shear blade 12 moves laterally relative to the seal assembly 30, the wiper 50 may clean the sealing surface 58 of the shear blade 12 starting at a leading edge 78 of the shear blade 12. As the shear blade 12 continues to move laterally with respect to the seal assembly 30, the cleaned section of the sealing surface 58 may move under the sealing element 52 of the seal assembly 30. At this time, the sealing surface 58 may be separated from the sealing element 52 by a certain distance. Even when the wiper 50 is pushed against the portion 76 of the sealing element 52 as shown in
This movement 90 of the energizer 54 may push against the sealing element 52, causing the sealing element 52 to deform into a sealing engagement with the sealing surface of the shear blade 12. This deformation is illustrated via arrow 92. The sealing element 52 may be constructed from rubber or some other elastomeric material that can deform in response to movement of the energizer 54 and form a fluid-tight seal upon its activation.
The energizer 54 may displace a relatively large amount of material of the sealing element 52 upon its activation, compared to the wiper 50 upon its activation. This is due in part to the energizer 54 having a larger width that the wiper 50, allowing the energizer 54 to compress a larger surface area of the sealing element 52. In addition, as shown in
As a result of this construction, when the shear blade 12 pushes against the energizer 54, the energizer 54 may displace a relatively large amount of the sealing element 52 toward the shear blade 12 to energize the seal. The wiper 50, on the other hand, may only displace enough of the sealing element 52 to cushion the movement of the wiper 50 and bias the wiper 50 toward the shear blade 12, without the sealing element 52 moving into contact with the seal blade 12. Thus, the sealing element 52 may remain above the level of the shear blade 12 until the energizer 54 activates the sealing element 52.
In some embodiments, the energizer 54 may include another sloped surface 94, which faces and abuts the sealing element 52. This sloped surface 94 may help direct the sealing element 52 as it is pushed by the energizer 54. That is, the sloped surface 94 may direct the sealing element 52 to deform in a direction toward the cleaned sealing surface of the shear blade 12.
In some embodiments, it may be desirable for the seal assembly 30 to be disposed along the shear blade 14 in a shape that matches or substantially matches a blade profile of the opposing shear blade 12. For example, the curved seal assembly 30 provided in
In other embodiments, the seal assembly 30 may be shaped to extend relatively straight across the width of the shear blade 14 while the other shear blade 12 is curved, or the seal assembly 30 may be curved (e.g.,
As shown in
The lip 110 of the energizer 54 may prevent the sealing element 52 from deforming into an exposed space between the shear blades 12 and 14 that is present when the shear blades 12 and 14 are in a closed position for forming the seal. For example, in the ram unit 10 of
While the 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. However, it should be understood that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the following appended claims.
