Abstract:
A method of reducing hydraulic shock in a BOP system including a pressure regulator having an input port and an output port, and a regulator piston that moves between an open and a closed position based on a change in hydraulic pressure applied to the regulator piston via a pilot port. The method includes initiating a function, and monitoring the state of the function as it is carried out to predict when the function nears the end of its cycle. The method also includes, when the function reaches a predetermined state, adjusting the hydraulic pressure on the regulator piston via the pilot port to gradually move the regulator piston between the open to the closed position to reduce fluid flow through the fluid path in a controlled manner to reduce hydraulic shock.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    Embodiments disclosed herein relate generally to pressure regulators. In particular, embodiments disclosed herein relate to pressure regulators wherein flow is controlled by pilot pressure. 
         [0003]    2. Brief Description of Related Art 
         [0004]    Drilling systems are often employed to access and extract oil, natural gas, and other subterranean resources from the earth. These drilling systems may be located onshore or offshore depending on the location of a desired resource. Further, such systems include a wide array of components, such as valves, that control drilling or extraction operations. Often, some of these components are controlled through pressure variation, such as that provided by a hydraulic control system. 
         [0005]    In some such systems, a hydraulic pressure regulator may be used to provide a fluid at a regulated working fluid pressure to downstream components, such as, for example, solenoid valves or BOP rams. One common type of hydraulic pressure regulator has a control piston that moves back and forth to open and close both supply ports and vent ports of the regulator in response to the magnitude of pressure within the regulator. As the control piston in the regulator moves toward a closed position, the operator piston in the associated function correspondingly moves toward a closed position, and the sudden reduction in flow can lead to vibrations in the downstream components. Such vibrations are known as fluid hammer, or water hammer. Such vibrations can degrade equipment and, over time, can lead to equipment failures and other problems. 
       SUMMARY OF THE INVENTION 
       [0006]    One embodiment of the present technology provides a method of reducing hydraulic shock in a BOP system, the BOP system including a pressure regulator having an input port and an output port, and a regulator piston that moves between an open and a closed position based on a change in hydraulic pressure applied to the regulator piston via a pilot port, the open position creating a fluid path between the input port and the output port so that fluid can flow therebetween, and the closed position severing the fluid path. The method includes the steps of initiating a function, and monitoring the state of the function as it is carried out to predict when the function nears the end of its cycle. The method further includes transmitting information about the state of the function to a controller that controls the amount of hydraulic pressure applied to the regulator piston via the pilot port, and determining when the function reaches a predetermined state prior to the end of its cycle. In addition, the method includes when the function reaches the predetermined state, and adjusting the hydraulic pressure on the regulator piston via the pilot port to begin moving the regulator piston toward the closed position. 
         [0007]    An alternate embodiment of the present technology provides a method of opening and closing a fluid flow path through a pressure regulator. The method includes the steps of providing an input port, and output port, and a pilot port at discrete locations on a housing of the pressure regulator, and providing a regulator piston within the housing. The regulator piston is movable within the housing along a longitudinal axis of the regulator piston, and has a hollow portion that allows fluid flow through the regulator piston. The regulator piston is in an open position when the hollow portion at least partially aligns with the input and output ports so that fluid flows between the input and output ports, and in a closed position when the hollow portion is not aligned with the input and output ports. The method further includes the step of controlling movement of the regulator piston between open and closed positions by adjustment of hydraulic pressure on the regulator piston, such hydraulic pressure provided via the pilot port. 
         [0008]    Yet another embodiment of the present technology provides a hydraulic shock reducing pressure regulator for controlling a function on a BOP stack, including a housing having an input port, an output port, and a pilot port, and a regulator piston having a hollow portion and surrounded by the housing. The regulator piston is movable within the housing between an open position and a closed position, the regulator piston in the open position when the hollow portion connects the input port with the output port to allow pressure communication between the input port and the output port, and in the closed position when the hollow portion is misaligned from either the input port or the output port or both so that there is no pressure communication between the input port and the output port. In addition, a portion of the regulator piston is in pressure communication with the pilot port so that controlled changes in pressure in the pilot port move the regulator piston between the open position and the closed position and vice versa. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present technology will be better understood on reading the following detailed description of nonlimiting embodiments thereof, and on examining the accompanying drawings, in which: 
           [0010]      FIG. 1  shows an isometric view of a pressure regulator according to an embodiment of the present technology; 
           [0011]      FIG. 2  shows a side view of a BOP stack according to an embodiment of the present technology, including the pressure regulator of  FIG. 1 ; 
           [0012]      FIG. 3  shows a cross-sectional view of the pressure regulator of  FIG. 1  taken along line  3 - 3  of  FIG. 1 , with the regulator piston in the open position; 
           [0013]      FIG. 4  shows a cross-sectional view of the pressure regulator of  FIG. 1  taken along line  3 - 3  of  FIG. 1 , with the regulator piston in the closed position; 
           [0014]      FIG. 5A  is a graphical representation of the position of a known function during a stroke thereof; 
           [0015]      FIG. 5B  is a graphical representation of the pressure during the stroke of the function of  FIG. 5A , including hydraulic shock; 
           [0016]      FIG. 6  is a diagram of a hydraulic circuit including a pressure regulator according to an embodiment of the present technology; 
           [0017]      FIG. 7  is a graphical representation showing position of a function controlled using a pressure regulator of an embodiment of the present technology; 
           [0018]      FIG. 8A  is a chart showing the relationship of fluid flow to pilot pressure in a pressure regulator of the present technology when the pilot pressure is set at a predetermined level; 
           [0019]      FIG. 8B  is a chart showing the relationship of fluid flow to pilot pressure in a pressure regulator of the present technology when the pilot pressure is set at an alternate predetermined level to that shown in  FIG. 8A ; 
           [0020]      FIG. 8C  is a chart showing the relationship of fluid flow to pilot pressure in a pressure regulator of the present technology when the pilot pressure is set at an alternate predetermined level to that shown in  FIGS. 8A and 8B ; and 
           [0021]      FIG. 8D  is a chart showing the relationship of fluid flow to pilot pressure in a pressure regulator of the present technology when the pilot pressure is set at an alternate predetermined level to that shown in  FIGS. 8A-8C . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0022]    The foregoing aspects, features, and advantages of the present technology will be further appreciated when considered with reference to the following description of preferred embodiments and accompanying drawings, wherein like reference numerals represent like elements. The following is directed to various exemplary embodiments of the disclosure. The embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, those having ordinary skill in the art will appreciate 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 suggest that the scope of the disclosure, including the claims, is limited to that embodiment. 
         [0023]    Referring now to the drawings,  FIG. 1  depicts a pressure regulator  10  according to one example embodiment of the present technology. The pressure regulator  10  includes a regulator body  12  and a series of ports, described in greater detail below. 
         [0024]      FIG. 2  in turn depicts a BOP stack assembly  16 , including a lower marine riser package (LMRP)  17 , with the pressure regulator  10  attached thereto, and a lower stack  19 . The LMRP  17  includes, among other components, control pods  21  for controlling components of the BOP stack  16  assembly. The LMRP conducts fluid from a riser (not shown) through the control pods  21  to the lower stack  19 . 
         [0025]    The lower stack  19  includes typical BOP features, such as, for example, a frame  18  with a wellhead connector  20  at the lower end for connecting to a subsea wellhead assembly (not shown). Typically, a bore runs through the BOP stack assembly  16 , including the lower stack  19 , which bore may contain a pipe. A shear ram housing  22  is typically located above a pipe ram housing  24 . The shear ram housing  22  contains shear ram blocks (not shown) positioned to close across the bore and shear the pipe in an emergency, to seal off the well. The pipe ram housing  24  contains pipe ram blocks (not shown) positioned to close across the bore and seal around the pipe, thereby sealing the annulus around the pipe. In the embodiment shown in  FIG. 2 , there are multiple sets of ram housings. 
         [0026]    In some embodiments, the pressure regulator  10  of the present technology can be hydraulically coupled to the shear and/or pipe ram housings to provide hydraulic pressure to close the shear and/or pipe ram blocks, as explained in greater detail below. The pressure regulator  10  can also be used to hydraulically control other components of the BOP stack, such as, for example, choke and kill valves. 
         [0027]    Referring now to  FIG. 3 , a cross-sectional view of a pressure regulator  10  in accordance with one or more embodiments of the present technology is shown. The pressure regulator  10  includes a regulator body  12 . A regulator piston  26  is slidably disposed within the regulator body  12 . In  FIG. 3 , the regulator piston  26  is shown to consist of two separate parts. This design allows for ease of assembly during the manufacturing process. In other embodiments, the regulator piston can consist of a single part, or more than two parts. The regulator piston  26  is in fluid communication with an outlet  28  of the regulator body  12  via path  30 , as well as an inlet  31 . The outlet  28  in turn is in communication with a function, such as, for example, a pair of BOP rams or a valve. One purpose of the pressure regulator  10  is to help maintain a constant pressure at the outlet  28 . The inlet  31  is in communication with a supply of fluid, such as a hydraulic system or an accumulator. 
         [0028]    The regulator piston  26  includes an internal passage  32 , which in turn includes a longitudinal piston bore passage  34  and a transverse piston bore passage  36  that intersects the longitudinal piston bore passage  34 . The regulator body  12  can also include regulator caps  38  that attach to and seal ends of the regulator body  12 . One of the regulator caps  38  has a protrusion  40  that extends into the regulator body  12 . The protrusion is hollow and encloses a longitudinal cap bore passage  42  and a transverse cap bore passage  44  that intersects the longitudinal cap bore passage  42 . The longitudinal cap bore passage  42  can be coaxial with the longitudinal piston bore passage  34 . As shown, the longitudinal piston bore passage  34  is of sufficient diameter to accept insertion of at least a portion of the protrusion  40  so that when the regulator body  12  is fully assembled, the regulator piston  26  surrounds a portion of the protrusion  40 . The regulator piston  26  is axially moveable relative to the protrusion  40 , and the interface between the regulator piston  26  and the protrusion  40  is guided with a regulator piston bearing  46 . The end of the protrusion  40  is open so that fluid is free to flow between the longitudinal piston bore passage  34  and the longitudinal cap bore passage  42 . 
         [0029]    In addition to the above, the regulator  10  also includes a pilot port  47  that controls hydraulic pressure to an end of the regulator piston  26  opposite the internal passage  32  of the regulator piston  26 . Such hydraulic pressure can be increased by introducing fluid through the pilot port  47  into the space  49  adjacent the end of the regulator piston  26 , and decreased by removing fluid from the space  49 . One purpose of the pilot port  47  is to help move the regulator piston  26  between open and closed positions by increasing and decreasing the hydraulic pressure on the regulator piston  26 . 
         [0030]    Also as shown in  FIG. 3 , the regulator  10  can optionally include a pressure read back port  51 , the purpose of which is to provide access to the inside of the housing  12  for taking a pressure reading inside the housing  12 , which pressure reading may be used to help determine the appropriate pressure to provide in space  49  via the pilot port  47 . The pressure regulator  10  also includes a vent port  53 . At times the pressure in the outlet  28  can exceed the pilot pressure in space  49 . When this occurs, such high pressure in the outlet  28  can move the regulator piston  26  further toward the closed position, until the transverse piston bore passage  36  partially aligns with the vent port  53 . Such alignment allows venting of fluid from the regulator via the vent port  53  until the pressure in the outlet  28  returns to the pilot pressure in space  49 , and the regulator piston  26  returns to the closed position shown in  FIG. 4 . 
         [0031]    The functionality of the regulator  10  will now be described in reference to  FIGS. 3 and 4 . In the drawings,  FIG. 3  shows the regulator  10 , with the piston in an open position (with a flow path open between the inlet  31  and the outlet  28  along path  30 ). As discussed above, the regulator piston  26  is in constant fluid communication with an outlet  28  of the regulator body  12  regardless of its position within the regulator housing  12 . In the open position of  FIG. 3 , the transverse piston bore passage  36  is in fluid communication with the inlet  31  via path  30  as well. Typically, the regulator piston  26  is in the open position because the pressure at the outlet  28  is lower than desired. To remedy this deficiency in pressure, a fluid at the inlet  31  can be provided that is at a higher pressure than the desired pressure at the outlet  28 . 
         [0032]    For example, in the example embodiment of  FIG. 3 , if the pressure at the outlet  28  is less than 3,000 psi, and an operator desires to raise the pressure at the outlet  28  to 3,000 psi, then a fluid can be provided at the inlet  31  that is higher than 3,000 psi. The higher pressure at the inlet  31  in this embodiment raises the pressure at the outlet  28 . 
         [0033]    Referring now to  FIG. 4 , the regulator piston  26  is shown in the closed position (without a flow path between the inlet  31  and the outlet  28 ). In the closed position, the transverse piston bore passage  36  is not aligned with the inlet  31 , such that the only fluid path into or out of the longitudinal or transverse piston bore passages  34 ,  36  is through the outlet  28 . Movement of the regulator piston  26  between the open position of  FIG. 3  and the closed position of  FIG. 4  can be effected by lowering the hydraulic pressure in space  49  adjacent the end of the regulator piston  26 . This lowering of hydraulic pressure can be accomplished by removing fluid from space  49  via pilot port  47 . 
         [0034]    One problem that can occur as the regulator piston  26  moves from the open to the closed position is hydraulic shock, or water hammer, in the function. Water hammer occurs when a fluid in motion is forced to suddenly stop or change direction.  FIGS. 5A and 5B  are graphs that illustrate position and pressure gradients, respectively, of functions of some known systems as they close, and are meant to illustrate the problem of water hammer that the invention of the present technology addresses. Although the water hammer illustrated in  FIGS. 5A and 5B  occurs in the function itself, movement of an operator piston in the function corresponds to, and is controlled by, the movement of the regulator piston  26  in the regulator  10 . 
         [0035]    Referring now to  FIG. 5A , there is shown the stroke of some known functions in terms of the position of the function over time. As shown, prior to initiation of the function, its position is static, as shown in portion  50  of the graph. In portion  52  of the graph, the position of the function changes as the function moves from an open position, indicated by line  55 , toward a closed position, indicated by line  57 . When the function reaches the closed position, it does so suddenly, and movement of an operating piston of the function stops moving almost immediately. This sudden stop at the end of the stroke is shown by the sharp angle  59  that occurs at the closed position  57 . 
         [0036]    The graph in  FIG. 5B  shows the pressure corresponding to the function throughout the stroke of  FIG. 5A , including the phenomenon of water hammer that occurs in many known systems. Specifically, portion  74  of the graph shows the pressure of the fluid in the function when the function is fired. During this phase, the function is just beginning to move. Portion  76  of the graph shows the pressure of the fluid in the regulator while the function is actuating. As shown, during this phase, the pressure is lower than in the previous phase, but still steady. Portion  80  of the graph shows what typically happens when the function is completed. As the function completes, the function suddenly moves to the closed position and the pressure initially spikes, and then oscillates until it reaches equilibrium. This is water hammer, and it has the ability to damage components of the BOP system. 
         [0037]    One way to reduce or eliminate water hammer in components of a BOP system is to better control the movement of the regulator piston  26  in the regulator  10  during a portion of the stroke between the open and closed positions, because such movement of the regulator piston  26  corresponds to movement of the operator piston in a function. This can be accomplished using the pilot port  47 , as controlled by a controller  56  (shown in  FIG. 6 ). The diagram of the hydraulic circuit  58  of  FIG. 6  is designed to emulate a BOP control system, and is useful to show how the pilot port  47  and controller  56  can be structured and function to control a valve  59  or other BOP component, according to an example embodiment of the present technology. The controller  56  can be any device capable of receiving data and using logic to generate an output signal. For example, the controller  56  can be a programmable logic controller (PLC). 
         [0038]    As shown in  FIG. 6 , hydraulic fluid used to actuate the valve  59  (or other function in the lower BOP stack  16 ) is stored in a fluid reservoir  60 . The fluid is pumped, using a pump  62 , to the regulator  10 . The flow rate of the fluid between the fluid reservoir  60  and the regulator  10  can be measured using a flow meter  64 , and its pressure can be measured using the pressure sensor  66 . An accumulator  68  can be provided to supplement the flow if needed. Although a single accumulator  68  is shown for the sake of clarity, any number of accumulators can be used in systems of the present technology. 
         [0039]    The regulator  10  can be structured as shown in  FIGS. 3 and 4 , and the position of the regulator piston  26  within the regulator  10  can be controlled using a pair of valves  70 ,  71  connected to the controller  56  and the pilot port  47 . In practice, the controller  56  receives data related to the state of the function, as described in greater detail below, and determines whether to add fluid to the regulator  10  via the pilot port  47 , thereby pushing the regulator piston  26  toward an open position, or to remove fluid from the regulator  10  via the pilot port  47 , thereby moving the regulator piston  26  toward a closed position. For example, valve  71  can be opened to supply fluid to the pilot port  47  of regulator  10  from a source  73  to increase pressure in space  49  of the regulator  10 . Alternately, valve  70  can be opened to vent fluid from space  49  of the regulator  10  to decrease pressure in the regulator  10 . 
         [0040]    When the regulator piston  26  is in the open position, fluid flows out of the regulator  10  through the outlet  28  and to the valve  59 , or other function. The pressure of such fluid can be measured using pressure sensor  72 . 
         [0041]    To avoid water hammer in the regulator  10  after the function is fired, the controller  56  can receive information about the pressure of the fluid leaving the regulator  10 , as well as about the position of the valve  59 , or a function associated therewith. As the valve  59  nears its closed position, and/or an associated function nears the end of its stroke, the controller  56  can begin to reduce the hydraulic pressure in space  49 , thereby beginning the process of moving the regulator piston  26  into the closed position before the function is fully completed. In this way, the controller  56  can gradually reduce the flow of fluid through the regulator as the function completes, and avoid the sudden stop of fluid flow through the regulator  10 . Because the movement of the regulator piston  26  toward the closed position corresponds to movement of the valve  59 , and in turn to the movement of associated functions controlled by the regulator  10  toward a closed position, such gradual movement of the functions at the end of their cycles will correspondingly lead to a gradual reduction in flow through the functions, thereby reducing water hammer in the functions. The controller  56  can be controlled by an algorithm tailored to the specific functions regulated by the regulator  10 . 
         [0042]    The graph in  FIG. 7  shows the position of a function as the function is carried out using the regulator  10  of the present technology. The graph of  FIG. 7  can be compared to that of  FIG. 5A  to visualize some of the distinctions between known systems (represented in  FIG. 5A ) versus systems of embodiments of the present technology (shown in  FIG. 7 ). In  FIG. 7 , portion  50 ′ of the graph shows the steady position of a function before the function is fired. Portion  52 ′ of the graph shows the position of the function while the function is actuating. As shown, during this phase, the function moves at a relatively steady pace through the first part of its stroke. 
         [0043]    Before the function is complete, however, such as at the time indicated by line  78 , the controller  56  (which receives information about the state of the function as it is carried out) begins to move the regulator piston  26  in the regulator  10 , toward the closed position using the pilot port  47 . This allows a gradual diminishing of the flow rate through the regulator  10 , and a corresponding slowing of the function, as the function nears completion. Finally, portion  54 ′ of the graph shows the steady state of the closed position when the function is completed. Notably, between time  78 , when the function begins to slow, and time  57 ′, when the function is complete, the position of the function gradually slows. The result is that the end of the stroke is defined by a gradual curve  59 ′, in contrast to the sudden stop indicated by the angle  59  of  FIG. 5A . By avoiding the sudden stop at the end of the stroke, water hammer can be reduced or eliminated. 
         [0044]    One surprising feature of the present technology is that adjustment of the hydraulic pressure in space  49  via the pilot port  47  alone will move the regulator piston  26  and reduce flow rate through the regulator  10 . The benefit to this feature is that controlling the movement of the regulator piston  26  during operation of the regulator  10  is simplified, because an operator need only control the pressure into the pilot port  47  to control the regulator piston  26 . Although the pilot pressure alone can move the regulator piston  26  toward a closed position, in some embodiments, a spring or other device can also be employed to help move the regulator piston  26 . 
         [0045]      FIGS. 8A-8D  are charts depicting experimental results related to the correlation between the pilot pressure and flow rate in the regulator  10 . Of course, the flow rate through the regulator  10  is directly related to the position of the regulator piston  26 , which is controlled by the pilot pressure.  FIG. 8A  shows that when the pilot pressure is set relatively high (4,000 psi), the flow rate remains high as well (about 400 GPM). As illustrated in the charts of  FIGS. 8B, 8C, and 8D , however, as the pilot pressure drops, so does the flow rate. For example, a pilot pressure of 1,250 psi in  FIG. 8B  corresponds to a flow rate of less than 350 GPM. Similarly, a pilot pressure of 1,000 psi in  FIG. 8C  corresponds to a flow rate of about 275 GPM, and a pilot pressure of 750 psi corresponds to a flow rate of only about 175 GPM. 
         [0046]    While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the disclosure as described herein. Accordingly, the scope of the disclosure should be limited only by the attached claims.