Abstract:
A system includes a blowout preventer (BOP) including a shear ram assembly. The shear ram assembly includes a first shear ram block having a first forward end, a first blade having a first forward face and extending from the first shear ram block, a face bolt passage extending into the forward end of the shear ram block, a face bolt positioned within the face bolt passage configured to couple the first blade to the first shear ram block, and a first seal containment encapsulated by the first shear ram block.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. provisional patent application No. 62/252,913, filed on Nov. 9, 2015, the entire contents of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    Embodiments of the subject matter disclosed herein generally relate to oil and gas wells, and in particular to an improved blind shear ram for a blowout preventer (BOP) to be utilized in oil and gas wells. 
       BACKGROUND 
       [0003]    Blowout preventers (BOPs) are typically used in subsea drilling operations to protect an oil well from pressure surges in the well. Generally, BOPs include a series of rams aligned with a central bore. A drill pipe extends through the central bore and into the well below the BOP. Each set of rams is typically positioned with one ram on either side of the central bore. Some rams are designed to seal against the drill string when closed, but not to cut the drill string. Other rams include blades, and are designed to shear the drill string (and anything else in the central bore) when the rams are closed to completely seal the top of the well. These are referred to as shear rams. 
         [0004]    A typical BOP includes a bore that runs through the BOP and connects to a wellbore. Pipe and tools are introduced to the wellbore through the bore in the BOP. Generally, blind shear rams are included in a BOP stack, and are used to shear pipe or tools inside a bore where containment of the pressure within the bore is necessary, such as in a situation where an unexpected pressure surge in the well poses a danger to personnel on a rig or other well site. 
         [0005]    Blind shear rams typically include shear ram blocks that are mounted inside a housing, or bonnet, on the BOP. The shear ram blocks have blades that are attached to the front ends thereof, toward the bore. When the shear rams are activated, pistons push the shear ram blocks within the housing, causing the shear ram blocks and blades to close across the bore, simultaneously shearing any pipe, tools, or other objects in the bore and sealing the well. As the shear rams close, the shear ram blocks and blades are exposed to the wellbore pressure, which may be very high, such as more than 15,000 pounds per square inch (psi). 
         [0006]    Some existing shear ram designs utilize bolts or other fasteners to attach the ram blades to the shear ram blocks. Usually such bolts are passed through the front face of the blade into the block. However, drilling holes through the face of the blade for the fastener may degrade the blade, and may introduce stress paths. In addition, the positioning of the fasteners on the blade requires staggering of the height of the bolts on the blade, leading to uneven distribution of stresses in the bolts under pressure. As a result, it is common for bolts to fracture at pressures higher than about 15,000 psi. 
         [0007]    In today&#39;s oil and gas industry, however, drilling operations are moving into ever deeper water, which causes ever higher pressures in the wellbore. It is not uncommon, for example, for a BOP to sit on top of a well whose pressure is greater than 15,000 psi, and even up to about 20,000 psi or more, thereby exceeding the operational constraints of known BOP blind shear rams. It may be useful to provide an improved blind shear ram for a BOP suitable in withstanding high pressure and corrosive deep-water environments. 
       SUMMARY OF THE INVENTION 
       [0008]    In accordance with one or more embodiments, a system includes a blowout preventer (BOP) including a shear ram assembly. The shear ram assembly includes a first shear ram block having a first forward end, a first blade having a first forward face and extending from the first shear ram block, a face bolt passage extending into the forward end of the shear ram block, a face bolt positioned within the face bolt passage configured to couple the blade to first the shear ram block, and a first seal containment encapsulated by the first shear ram block. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings: 
           [0010]      FIG. 1  is a perspective view of a BOP stack assembly attached to a wellhead, in accordance with the present embodiments; 
           [0011]      FIG. 2  is a perspective view of upper and lower blind shear rams in a closed position, including a sheared pipe, in accordance with the present embodiments; 
           [0012]      FIG. 3A  is a perspective view of a shear ram block and blade, in accordance with the present embodiments; 
           [0013]      FIG. 3B  is a cross-sectional side view of the shear ram block and blade of  FIG. 3A  taken along line  3 B- 3 B, in accordance with the present embodiments; 
           [0014]      FIG. 4  is a perspective view of a shear ram block and blade, in accordance with the present embodiments; 
           [0015]      FIG. 5  is a perspective view of a shear ram block and blade, in accordance with the present embodiments; 
           [0016]      FIG. 6  is a perspective view of a shear ram block and blade, in accordance with the present embodiments; and 
           [0017]      FIG. 7  is a perspective view of a shear ram block and blade, in accordance with the present embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The foregoing aspects, features, and advantages of the present embodiments will be further appreciated when considered with reference to the following description of preferred embodiments and accompanying drawings, wherein the reference numerals represent like elements. In describing the preferred embodiments of the technology illustrated in the appended drawings, specific terminology will be used for the sake of clarity. However, the technology is not intended to be limited to the specific terms used, and it is to be understood that each specific term includes equivalents that operate in a similar manner to accomplish a similar purpose. 
         [0019]    In  FIG. 1 , there is shown a typical subsea BOP assembly, including a lower stack assembly  2 , and an upper stack assembly  4 , or lower marine riser package (LMRP). The upper stack assembly  4  may include, for example, a riser adapter  6 , annular blowout preventers  8 ,  10 , control pods  11 , and choke and kill lines  13 . The lower stack assembly  2  may include a frame  12  with a wellhead connector  14  at the lower end for connecting to a subsea wellhead assembly (not shown), as well as hydraulic accumulators  15 . Typically, a bore runs through the BOP assembly, including through the upper and lower stack assemblies  2 ,  4 , which bore may contain a pipe. A shear ram housing  16  is normally located above pipe ram housings  18 ,  20 ,  22  on the lower stack assembly. The shear ram housing  16  contains shear upper and lower ram shear blocks  24 ,  26  attached to upper and lower blades  28 ,  30  (shown in  FIG. 2 ). Each pipe ram housing  18 ,  20 , and  22  includes pipe ram blocks (not shown) with semi-circular recesses on the mating faces for closing around different size ranges of pipe. When open the shear and pipe ram blocks are positioned on either side of the bore. When closed, the shear ram blades  28 ,  30  seal off the bore. If pipe is present in the bore, the shear ram blades  28 ,  30  will shear the pipe. 
         [0020]    Referring now to  FIG. 2 , there are shown upper and lower shear ram blocks  24 ,  26  removed from the shear ram housing  16  and in a closed position. The upper shear ram block  24  has a lateral surface that defines a face or forward end  32 . The upper blade  28  mounts to the forward end  32  of the upper ram block  24 . The upper blade  28  has a forward face  36  with an upper edge  38  and a lower forward edge  40 . For purposes of this disclosure, the term forward, with reference to the ram blocks and associated components, shall mean from forward end  32  of upper shear ram block  24  toward the face  36  of the blade  28 . In the example shown in  FIG. 2 , the lower forward edge  40  of the upper blade  28  extends farther forward from the forward end  32  of the upper shear ram block  24  than does upper edge  38 . Face  36  of the upper blade  28  may also be generally concave or converging, resulting in the center of face  36  being recessed relative to the more forward portions of the face  36  at outer ends  42 ,  44 . Of course, different shapes for the upper blade  28  may be employed. As may be seen, when the shear ram blocks  24 ,  26  are closed, the blades  28 ,  30  overlap, thereby shearing pipe  46  positioned between the ram blocks  24 ,  26  in the bore of the BOP. 
         [0021]    Referring to  FIGS. 3A and 3B , there is shown a perspective view ( FIG. 3A ) and a cross-sectional side view ( FIG. 3B ) of the upper shear ram block  24  and blade  28  in accordance with the present embodiments. To better understand the advantages provided by the present techniques, it is useful to understand the forces acting on the upper shear ram block  24  and the blade  28  during the closing of the shear rams. As the upper shear ram block  24  moves forward to close, the fluid below the upper blade  28  exerts an upward force F on the bottom of the upper blade  28 , which may be very high, in some instances exceeding 15,000 psi or 20,000 psi. This upward force F, and in particular that portion of the upward force F acting at or near the forward edge  40  of the blade  28 , causes the blade to rotate away from the upper shear ram block  24 , and creates a moment M about one or more fasteners  48  (e.g., attachment bolts or cap screws) at the interfaces between the upper blade  28  and the upper shear ram block  24 . The features of the present embodiments increase the ability of the upper shear ram block  24  and blade  28  to withstand high pressures by, for example, improving such things as the orientation of the fasteners  48 , and the profile of the interface between the upper shear ram block  24  and blade  28 . 
         [0022]    For example, in the embodiment of  FIGS. 3A and 3B , the upper blade  28  is attached to the upper shear ram block  24  using a number of fasteners  48  that are inserted through the upper surface of the upper shear ram block  24  at an angle and into the upper blade  28  through the back surface  50  of the upper blade  28 . Such fastening of the blade  28  to the upper shear ram block  24  through the back surface  50  of the blade  28  is advantageous because it reduces or eliminates the use of an increased number of fasteners to pass through the face  36  of the blade  28 , and thereby strengthening the blade  28  and reducing possible stress paths through the blade  28 . In  FIGS. 3A and 3B , the number of fasteners  48  used to attach the upper blade  28  to the upper shear ram block  24  may include 5 or more fasteners  48 , but more or fewer bolts may be used without departing from the spirit and scope of the present embodiments. The fasteners  48  may be made from a high strength material such as, for example, high-strength alloy or various other materials that may not be brittle or prone to cracking or significant degradation. For example, an advantage to angling the fasteners  48  through the upper shear ram block  24  and into the back of the blade  28  is that the fasteners  48  may engage the back of the blade  28  in the middle or upper portions of the blade  28 , in which the blade  28  has little contact with pipe being sheared. This reduces the shear forces acting on the fasteners  48  compared to attachment at the lower portion of the blade  28 . 
         [0023]    Also depicted in  FIG. 3B  is an upper lip  52  of the upper shear ram  24  that extends forward over a portion of the upper blade  28 . This upper lip  52  helps to reduce rotation of the upper blade  28 , which rotation may be induced by pressure underneath the blade, as discussed above. The placement of the upper lip  52  above the blade  28  helps to block rotation of the blade  28 , thereby reducing the magnitude of the moment M at the fastener  48 . This is advantageous because it reduces stresses on the fasteners  48  and the upper blade  28 , thereby lowering the likelihood that the fasteners  48  or blade  28  will fracture or bend. 
         [0024]    Also depicted in  FIGS. 3A and 3B  is a lower lip  54  extending from the upper shear ram  24  below the upper blade  28 , and a seal  56  positioned between the upper blade  28  and the lower lip  54 . As the fasteners  48  are tightened, during attachment of the upper blade  28  to the upper shear ram  24 , the upper blade  28  is pulled in toward the lower lip  54 , thereby energizing the seal  56  and creating a tight hold on the seal  56 . 
         [0025]    In certain embodiments, the blade  28  may be utilized to encompass the seal  56 . The blade  28  is then maintained in place utilizing, for example, the fasteners  28  (e.g., or cap screws or bolts). However, as may be appreciated, due to high loads during pressure testing (e.g., greater than 15,000 psi or greater than 20,000 psi), the fasteners  28  (e.g., attachment bolts or cap screws) may include the use of a high torque to retain the blade  28  attached to the upper shear ram block  24 . As will be further appreciated with respect to  FIGS. 4-7 , by extending the front portion of the upper shear ram  24  to include the seal  56  as opposed to the blade  28  including the seal  56 , the high load demand may be removed from the blade  28  and the fasteners  48 , and, by extension, the upper shear ram block  24  and the BOP shear ram assembly  2 ,  4 . 
         [0026]    For example, in certain embodiments, as will be further appreciated, the upper shear ram block  24  may completely encapsulate the seal  56 . This may allow the upper shear blade block  24  to withstand higher hydrogen sulfide (H2S) concentrations, as well as higher pressures (e.g., greater than 15,000 psi or greater than 20,000 psi). The present techniques may also reduce the high preload currently required on the shear bolts of the blade  28 , and may eliminate, for example, a number of the fasteners  48  (e.g., attachment bolts or cap screws). Additionally, the present embodiments may reduce the high stress areas within the blade  28  by reducing, for example, bolt torque requirements. Furthermore, the present embodiments may maintain the seal  56  even when, for example, the blade  28  is damaged during operational shearing. 
         [0027]    With the foregoing in mind,  FIG. 4  depicts an isometric view of a blind shear ram  58  in accordance with the present techniques. For example, as illustrated, the seal  56  (e.g., lateral T-seal) is encapsulated by the upper shear ram block  24 , for example, as opposed to being included as part of the blade  28 . In this way, the number of fasteners  48  (e.g., attachment bolts or cap screws) may be reduced. Indeed, by providing the present techniques in which the seal  56  (e.g., lateral T-seal) is encapsulated by the upper shear ram block  24 , and thus removing any dependency on the blade  28  to encompass the seal  56 , the upper shear ram block  24  and the blade  28 , and, by extension, the complete BOP shear ram assembly  2 ,  4 , may be more suitable to be utilized within National Association of Corrosive Engineers (NACE) environments or other corrosive and deep-water environments (e.g., pressures greater than 15,000 psi or greater than 20,000 psi). Specifically, environments referred to herein as “NACE environments” may refer to any environment in which equipment or other assets may be subject to corrosion or any other degradation due to the surrounding environmental conditions (e.g., deep-water environments, underground environments, and so forth). Additionally, by including the seal  56  (e.g., lateral T-seal) as part of the upper shear ram block  24  (e.g., as opposed to being included as part of the blade  28 ), the number of bolts may be reduced, and thus any high-bolt preload load utilized for retention of the blade  28  may also be reduced. 
         [0028]    For example,  FIG. 5  depicts a top view of the blind shear ram  58  according to the present techniques. In certain embodiments, in accordance with the present techniques of including the seal  56  (e.g., lateral T-seal) as part of the upper shear ram block  24  (e.g., as opposed to being included as part of the blade  28 ), only 2 fasteners  48  (e.g., attachment bolts or cap screws) may be utilized to couple the blade  28  to the shear ram block  24  (e.g., as opposed to up to 5 or more fasteners  48  as illustrated with respect to the embodiment of  FIG. 3A ). 
         [0029]    Similarly,  FIG. 6  illustrates another embodiment of the blind shear ram  58  in which one more guide arms of the blind shear ram  58  are not depicted for the purposes of conciseness and clarity. Specifically,  FIG. 6  illustrates another view of the blind shear ram  58  in which the seal  56  (e.g., lateral T-seal) is encapsulated by the upper shear ram block  24  (e.g., as opposed to being included as part of the blade  28 ). In an alternative embodiment to that illustrated in  FIG. 6 , the upper shear ram block  24  may be machined to allow an attachment plate to facilitate an installation of the t-seal. In such an embodiment, the attachment plate may be located behind the seal  56  (e.g., lateral T-seal). 
         [0030]      FIG. 7  depicts a cross-sectional view of the blind shear ram  58  according to an embodiment of the present techniques. As depicted, the seal  56  (e.g., lateral T-seal) is encapsulated by the upper shear ram block  24  (e.g., as opposed to being included as part of the blade  28 ). For example, as further depicted in  FIG. 7 , the lower lip  54  extends from the upper shear ram block  24  below the blade  28  and encompasses the seal  56  along with the lower lip  54 . As previously noted, in this way, the number of fasteners  48  (e.g., attachment bolts or cap screws) may be reduced. Indeed, by providing the present techniques in which the seal  56  (e.g., lateral T-seal) is encapsulated by the upper shear ram block  24 , and thus removing any dependency on the blade  28  to encompass the seal  56 , the upper shear ram block  24  and the blade  28 , and, by extension, the complete BOP shear ram assembly  2 , 4 , may be more suitable to be utilized within NACE environments or other corrosive and deep-water environments (e.g., H2S environments and environments including pressures greater than 15,000 psi or greater than 20,000 psi). Additionally, by including the seal  56  (e.g., lateral T-seal) as part of the upper shear ram block  24  (e.g., as opposed to being included as part of the blade  28 ), the number of fasteners  28  (e.g., attachment bolts or cap screws) may be reduced, and thus any high-bolt preload load utilized for retention of the blade  28  may also be reduced or substantially eliminated. 
         [0031]    Technical effects of the present embodiments include an improved blind shear ram assembly to be utilized as part of blowout preventer (BOP) that includes a seal as part of the shear ram block of the blind shear ram assembly, as opposed to being included as part of the blade of the blind shear ram assembly. Indeed, by providing the present techniques in which the seal (e.g., lateral T-seal) is encapsulated by the upper shear ram block, and thus removing any dependency on the blade to encompass the seal, the upper and lower shear ram blocks and the blade, and, by extension, the complete BOP shear ram assembly may be more suitable to be utilized within NACE environments or other corrosive and deep-water environments (e.g., H2S environments and environments including pressures greater than 15,000 psi or greater than 20,000 psi). Additionally, by including the seal (e.g., lateral T-seal) as part of the upper shear ram block (e.g., as opposed to being included as part of the blade), the number of fasteners (e.g., attachment cap screws or bolts) may be reduced, and thus any high-bolt preload load utilized for retention of the blade may also be reduced. 
         [0032]    The disclosed exemplary embodiments provide an improved blind shear ram. It should be understood, however, that this description is not intended to limit the invention. On the contrary, the exemplary embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details. 
         [0033]    Although the features and elements of the present exemplary embodiments are described in the embodiments in particular combinations, each feature or element may be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein. 
         [0034]    This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.