Patent Publication Number: US-8979062-B2

Title: Secondary activation of packer and method

Description:
BACKGROUND 
     1. Technical Field 
     Embodiments of the subject matter disclosed herein generally relate to methods and devices and, more particularly, to mechanisms and techniques for increasing a pressure applied to a ram blowout preventer (BOP) for sealing a wellbore. 
     2. Discussion of the Background 
     One apparatus for sealing a well is the ram BOP. The ram BOP (herein simply BOP) is a safety mechanism that is used at a wellhead of an oil or gas well. The BOP may be used for offshore drilling and also for land-based drilling. The BOP is configured to shut the flow from the well when certain events occur. One such event may be the uncontrolled flow of gas, oil or other well fluids (e.g., mud) from an underground formation into the well. Such event is sometimes referred to as a “kick” or a “blowout” and may occur when formation pressure exceeds the pressure generated by the column of drilling fluid. This event is unforeseeable and if no measures are taken to prevent and/or control it, the well and/or the associated equipment may be damaged. 
     The BOP may be installed on top of the well to seal the well in case that one of the above events is threatening the integrity of the well. The BOP is conventionally configured to prevent the release of pressure either in the annular space between the casing and the drill pipe or in the open hole (i.e., hole with no drill pipe) during drilling or completion operations. 
     In this regard, the BOP has two ram blocks that are configured to move towards each other or away from each other as desired by the operator of the rig. The operator of the rig controls the closing and opening of the ram blocks by activating various valves that control a hydraulic fluid. The hydraulic fluid is either provided from accumulators provided next to the BOP (e.g., undersea for an undersea BOP) or through pipes from the surface. By allowing the hydraulic fluid under pressure to enter a closing chamber the ram blocks are closed and by allowing the hydraulic fluid to enter an opening chamber the ram blocks are opened. 
     The ram blocks have at their frontal faces an elastomeric material, a packer, that has a semi-spherical profile. Thus, when the drill line is still inside (i.e., crossing the BOP) and there is a need to close the well, the ram blocks close around the drill line and the profile of the packers ensure that an interface between the drill line and the ram blocks is sealed. It is noted that shearing ram blocks have cutting edges instead of packers and when there is a need to close the BOP, the shearing ram blocks will close the well by severing the drill line. 
     However, in practice it is noted that sometimes the interface between the packers and the drill line is not completely sealed, i.e., there is a leakage of mud or other fluids that are present in the well. The leak is more serious as the diameter of the drill line increases. Thus, there is a need in the industry to provide a better sealing when a ram block with a packer is used to close a well while a tool is still inside the BOP. 
     Accordingly, it would be desirable to provide systems and methods that achieve the sealing of the well irrespective of the diameter of the drill line and to avoid the above noted shortcomings. 
     SUMMARY 
     According to one exemplary embodiment, there is a ram blowout preventer (BOP) for sealing a well. The ram blowout preventer includes a body having a first chamber extending along a first direction and a second chamber extending along a second direction, substantially perpendicular to the first direction; a ram block configured to move inside the first chamber, the ram block having a packer region and at least one channel that extends all the way through the ram block; a packer configured to be provided in the packer region to seal a tool provided inside the second chamber; and at least one double piston provided through the at least one channel so that a pressure from the well is transmitted to the packer. 
     According to another exemplary embodiment, there is a ram block configured to move inside a first chamber of a ram blowout preventer (BOP). The ram block includes a packer region and at least one channel that extends all the way through the ram block; a packer configured to be provided in the packer region to seal a tool provided inside a second chamber of the BOP; and at least one double piston provided through the at least one channel so that a pressure from a well to which the BOP is attached is directly transmitted to the packer. 
     According to still another exemplary embodiment, there is a method for manufacturing a ram block for a ram blowout preventer. The method includes providing a ram block; forming a packer region in the ram block; forming at least one channel that extends all the way through the ram block; installing at least one double piston through the at least one channel; and installing a packer in the packer region so that a first piston side of the double piston contacts the packer when pressure is applied on a second piston side of the double piston. 
     According to yet another exemplary embodiment, there is a method of operating a ram blowout preventer (BOP) for sealing a well. The method includes activating a primary system for closing a ram block to seal with a packer a tool provided in the BOP; and applying well pressure on a double piston provided through at least one channel of the ram block so that a first piston side of the double piston directly applies a corresponding force on the packer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a schematic diagram illustrating a BOP with novel ram blocks according to an exemplary embodiment; 
         FIG. 2  is a schematic diagram of a back view of a ram block according to an exemplary embodiment; 
         FIG. 3  is a front view of a ram block according to an exemplary embodiment; 
         FIG. 4  is a back view of a ram block having two channels according to an exemplary embodiment; 
         FIG. 5  is an overall view of a double piston to be added to a ram block according to an exemplary embodiment; 
         FIG. 6  is a front view of a ram block having metal plates according to an exemplary embodiment; 
         FIG. 7  is an overall view of a packer having metal inserts according to an exemplary embodiment; 
         FIG. 8  is a top view of a ram block having a double piston according to an exemplary embodiment; 
         FIG. 9  is a flow chart of a method for assembling a ram block with a double piston according to an exemplary embodiment; and 
         FIG. 10  is a flow chart of a method for operating a BOP with ram blocks having double pistons according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to the terminology and structure of a ram BOP. However, the embodiments to be discussed next are not limited to these systems, but may be applied to other systems, i.e., a gate valve. 
     Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. 
     According to an exemplary embodiment, a ram BOP is configured to have ram blocks provided with at least one through-channel that accommodates a corresponding double piston. The double piston has a first face exposed to a fluid that is present in a wellbore and a second face that contacts a packer of the ram block. The pressure from the wellbore is exerted on the packer for a better sealing of a tool present in the BOP. 
     Novel features of this ram BOP are now discussed with regard to the figures.  FIG. 1  illustrates a cut view of a BOP  16 . The BOP  16  has ram blocks  20  configured to move along a longitudinal first chamber  18 . A second chamber  19 , substantially perpendicular on the first chamber  18 , is configured to accommodate a tool  21 , e.g., a drill line. The term “substantially” here means that even if the direction of the first chamber makes an angle in the range of 85 to 95 degrees with the direction of the second chamber, the two chambers are still considered perpendicular. Thus, the second chamber  19  is open while the first chamber  18  is closed. The ram blocks  20  are shown closed on the tool  21  inside the first chamber  18 . 
     A primary activation mechanism for the ram blocks  20  includes a closing chamber  22  and an opening chamber  24  (having a substantially zero volume when the ram blocks are closed as in  FIG. 1 ). A piston  26  is provided between the closing chamber  22  and the opening chamber  24 . A rod  28  is attached to the piston  26  and is also configured to connect to the ram block  20 . Thus, when pressure in the closing chamber  22  overcomes the pressure in the opening chamber  24 , the piston  24  moves to left in  FIG. 1 , closing the ram block  20  (i.e., pressing the ram block on the drill line  21 ). This is the primary system for applying pressure on the ram blocks and on the packers. A packer  30  is shown on a frontal face of the ram block  20 . The packer  30  contacts the drill line  21  for a better seal. 
     When a pressure in the wellbore  40  needs to be controlled, the ram blocks  20  are closed. The increasing pressure in the wellbore  40  determines the ram blocks  20  to be pressed upward, i.e., along a Z direction in  FIG. 1 . A seal  31  is provided on an upper part of the ram block  20  to achieve a seal between the ram block  20  and a body  42  of the ram BOP  16 . A further seal  44  may be provided to further increase the seal between the ram block and the body of the BOP. This means that a fluid present in the wellbore  40 , e.g., mud, may enter the first chamber  18  but should not be able to pass past the packer  30  into a first region  50  of the second chamber  19 . 
     The pressure of the wellbore that is present in the first chamber  18  may be used to apply further pressure on the packer  30  as discussed now with regard to  FIG. 2 .  FIG. 2  shows a side back view of a ram block  20 . The ram block  20  has a back portion  60  that is configured to connect to the rod  28  and a frontal portion  62  that is configured to hold the packer  30 . The frontal portion  62  is configured to face the drill line  21  when the ram blocks  20  are closed.  FIG. 2  also illustrates a groove  64  that is configured to accommodate seal  31  for achieving the seal between the body  42  of the ram BOP and the ram block  20 . 
     A channel  70  is illustrated in  FIG. 2  on the side of the ram block  20 . The channel  70  passes all the way through the ram block  20 , i.e., from a side that communicates with the first chamber  18  to a side that communicates with the packer  30 . One or more such channels  70  may be formed in each ram block  20 , depending on the type of ram block, its geometry, and the available space. 
       FIG. 3  is a front view of the ram block  20  and shows the other end of the channel  70 .  FIG. 3  also shows a packer region  66  that is configured to receive the packer  30 .  FIG. 4  is a back view of the ram block  20  and illustrates an embodiment in which there are two channels  70  per ram block  20 . Each channel  70  is configured to accommodate a double piston  80  as shown in  FIG. 5 . 
     The double piston  80  of  FIG. 5  has a central portion  82  that connects to two piston sides  84  and  86 . The piston side  84  is configured to directly contact the packer  30  while the piston side  86  is configured to contact the fluid existent in the wellbore. In one application, the size of the piston side  86  is larger than the size of the piston side  84  in order to multiply a pressure effect of the wellbore on the packer. The double piston  80  may be made of a metal or composite that can withstand the large pressures and temperatures existing in a wellbore and also the corrosive environment in the wellbore. A shape of the piston side  84  may be made to match a shape of the corresponding packer  30 . For example, the piston side  84  may have an elliptical shape. Various other shapes may be used. One or both of the piston sides  84  and  86  may be attached to the central part  82  by various means. Such means may be screws, welding, etc. 
       FIG. 6  shows an embodiment in which the channel  70  has a cross-section larger than a cross-section of the piston side  84 . Thus, a plate  90  is bolted with bolts  92  to the ram block  20  and the plate  90  has an opening configured to accommodate the piston side  84  as shown in the figure. Other mechanisms may be envisioned for providing the double piston  80  into the channel  70 . 
     The packer may be a conventional one piece elastomer or a more sophisticated one as shown in  FIG. 7 . The packer  100  shown in  FIG. 7  has plural metallic inserts  102  partially provided inside the elastomeric part  104 . The profile of the metallic inserts  102  and the flexibility of the elastomeric part  104  make the packer  100  to have a variable radius R. This means that a single packer  100  (variable radius packer) is configured to mate with drill lines (or other tools) having various diameters. For such a packer, the secondary pressure mechanism discussed above is more advantageous than for a conventional one piece elastomer that is designed for a drill line having a given radius. Thus, the sealing of the variable radius packer  100  can be improved by using the channels  70  and double piston  82 . 
     One advantage provided by one or more of the exemplary embodiments presented above is now discussed. A shape of a face of some of the packers is elliptical. Thus, when the ram blocks are closed to seal a tool, the packers do not completely seal the tool due to this specific shape. This problem is illustrated in  FIG. 8 .  FIG. 8  shows the at least one channel  70  through the ram block  20  and also the components of the double piston  80 , i.e., the first piston side  84  facing the packer  30  and the second piston side  86  facing a pressure well. As the packer  30  does not completely seal a region A defined by an interface between the tool  21  and the packer  30 , the extra pressure applied by the well fluid at  100  on the second piston side  86  helps to bring the packer  30  closer to the tool  21  in region A as the first piston side  84  directly presses the packer  30  toward the tool  21 . Thus, a better seal is achieved by using the double piston  80 . 
     In another application, a spring  102  or equivalent means is provided between the second piston side  86  and the body of the ram block  20  so that only a certain well pressure (above the threshold pressure established by the spring  102 ) is applied on the packer  30 . 
     According to an exemplary embodiment illustrated in  FIG. 9 , there is a method for manufacturing a ram block for a ram blowout preventer. The method includes a step  900  of providing a ram block ( 20 ); a step  902  of forming a packer region ( 64 ) in the ram block ( 20 ); a step  904  of forming at least one channel ( 70 ) that extends all the way through the ram block ( 20 ); a step  906  of installing at least one double piston ( 80 ) through the at least one channel ( 70 ); and a step  908  of installing a packer ( 30 ) in the packer region ( 64 ) so that a first piston side ( 84 ) of the double piston ( 80 ) contacts the packer ( 30 ) when pressure is applied on a second piston side ( 86 ) of the double piston ( 80 ). 
     According to another exemplary embodiment illustrated in  FIG. 10 , there is a method of operating a ram blowout preventer for sealing a well. The method includes a step  1000  of activating a primary system ( 22 ,  24 ,  26 ,  28 ) for closing a ram block ( 20 ) to seal with a packer ( 30 ) a tool ( 21 ) provided in the BOP ( 16 ); and a step  1002  of applying well pressure on a double piston ( 80 ) provided through at least one channel ( 70 ) of the ram block ( 20 ) so that a first piston side ( 84 ) of the double piston ( 80 ) directly applies a corresponding force on the packer ( 30 ). 
     The disclosed exemplary embodiments provide a ram block, blowout preventer and method for improving a seal between a packer and a tool in a BOP. It should be understood 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. 
     Although the features and elements of the present exemplary embodiments are described in the embodiments in particular combinations, each feature or element can 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. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other example are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements within the literal languages of the claims.