Patent Publication Number: US-9896907-B2

Title: Equalizer valve with opposed seals biased toward closed from rising pressure on either of opposed sides

Description:
FIELD OF THE INVENTION 
     The field of the invention is equalizer valves for subterranean tools such as barrier valves and more particularly equalizer valves insensitive to rising pressure on either side of the equalizer valve to stay in the closed position. 
     BACKGROUND OF THE INVENTION 
     Valves are ubiquitous in the downhole drilling and completions industry. As the purpose of valves is to selectively enable fluid communication through the valves, the formation of pressure differentials across valves is customary. Large differential pressures across a valve can not only affect the operation of the valve, but can result in damage to the valve due to the sudden inrush of fluid when the valve is opened. For example, ball valves are often used in the art as so-called barrier valves for at least temporarily shutting off production in a hydrocarbon well, which leads to very large pressure differentials. These large pressure differentials can result in the rotatable ball member of the valve to be pressed firmly against its housing, which causes large frictional forces between the ball and the housing and increased difficulty in opening the valve. The frictional forces and inrush of fluid to the valve when opened can cause damage to the valve such that it does not open, close and/or seal properly. Systems for equalizing pressure before opening barrier and similar valves have been developed, but the industry is always receptive of advances and alternatives in pressure equalization technology. 
     In view of the potential for large variations of pressure on either side of an equalizer valve when in the closed position, designs have been developed to maintain the valves in a closed position if the pressure on either side of a closed equalizer valve increases. One such design is described in U.S. Pat. No. 9,062,519. This design incorporates three seals two of which are dynamic seals  16  and  18  that define a chamber  46  that is pressurized with a control line  45 . Pressure applied in control line  45  overcomes the force of the return spring  50  to move a piston  12  to separate metallic components  30  and  40  at the lower extremity  42  of the assembly. Without pressure applied in line  45  rising pressure at opposed ends of the equalizer valve  14  in regions designated as P 1  and P 2  will simply force the already closed valve  14  to stay in the closed position. This happens as pressure from P 1  communicates to surface  36  which is larger than opposing surface  38  for a net closing force on piston  12 . Higher pressure from P 2  acts directly on surface  42  to push the piston in a direction that keeps surfaces  30  and  40  together for the closed position of valve  14 . 
     While this design accomplishes the purpose of keeping the equalizer valve closed when it experiences a rise in end pressure at P 1  or P 2  it leaves the metal to metal seal of surfaces  30  and  40  exposed to velocity effects and associated erosion when the equalizer valve is actuated to open with pressure in line  45 . Due to the annular piston design using surface  48  on piston  12  there need to be two opposed seals to define pressure chamber  46 . As a result there are three seals required to accomplish the result of keeping the valve in a configuration where pressure increases on opposed ends do not open the valve. 
     The present invention addresses such issues by using two seals and a flow configuration that allows placement of a metal to metal seal internally to the housing with a tortuous path to reach the metal to metal seal to protect it from erosion when the equalizer valve is actuated to open with a rod piston that bears directly on the movable valve member. Springs can be provided to overcome seal friction in the rod piston actuator. The actuation system is depth insensitive. A plenum covers the lower seal and component configuration is such that pressure from below is conducted to between the dynamic and metal to metal seal while pressure from above is conducted to a back side of a dynamic seal and an uphole side of the metal to metal seal with a net result of a closure force. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims. 
     SUMMARY OF THE INVENTION 
     An equalizer valve is configured to stay shut when pressure on one side or the other goes up. A dynamic seal and a metal to metal seal are located within the housing. Pressure from above is directed uphole of the metal to metal seal and downhole of the larger dynamic seal for a net closing force. Pressure from downhole is directed between the metal to metal and dynamic seals for a net force uphole to keep the metal seal closed. Normal operation is from a control line moving a rod piston to move a valve member to open the metal to metal seal for flow through the valve body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a section view of the equalizer valve in the closed position; 
         FIG. 2  is the view of  FIG. 1  in the open position; 
         FIG. 3  is an enlarged view of a portion of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1  a body  11  has an uphole connection  13  and a downhole connection  15  connected to opposed sides of valve  17  that is mounted in a tubular string  19 . Typically valve  17  is a barrier valve in a subterranean well but can be a number of other different tools. Connection  21  leads to a control line that is not shown that extends from a surface location. Pressure applied in control line  23  moves rod piston  25  against end cap  27  secured on top of tube  29 . Tube  29  ends at lower end  31  and inside plenum  33 . As better seen in  FIG. 3  plenum  33  has ports  35  that lead to chamber  37 . A circumferential projection  39  has an outer surface  41  that has a diameter D 2 . Dynamic seal  43  is retained by ring  45 ′ against shoulder  47  on tube  29 . Dynamic seal  43  is a dynamic seal with an outer diameter D 3 . Dynamic seal  43  seals against wall  49  in plenum  33 . Tube  29  has ports  51  that communicate with annular space  53  which further extends into elongated annular space  55  that houses springs  57  and  59  each of which are mounted to provide an uphole force on cap  27  to push against rod piston  25  to overcome seal friction in rod piston seals  61  to return the piston  25  from the  FIG. 2  to the  FIG. 1  position when pressure is removed from control line  23 . Space  53  has an outer dimension D 1  defined by surface  63 . Surfaces  65  on tube  29  and  67  on sub  69  form a metal to metal seal when forcibly abutted in  FIG. 1  which shows the run in position with no flow through tube  29  because the lower end  31  is sealed by plenum  33  and dynamic seal  43  and surfaces  65  and  67  being forced together for the metal to metal seal. Surfaces  67  and  69  schematically represent any type of seal although metal to metal is preferred but as used in this application the term “metal to metal seal” is intended to capture its known alternatives including face nonmetallic seals or elastomer seals, for example. Thus pressure from uphole called PA reaches through tube  29  to a dead end at dynamic seal  43  which has a diameter D 3  greater than diameter D 1  at surface  63  that is accessed through ports  51 . As a result raising pressure PA simply increases the net uphole force on tube  29  to hold surfaces  65  and  67  more firmly together. An increase in the pressure PB from downhole communicates through ports  35  to dynamic seal  43  to create a downhole oriented force against dynamic seal  43  as well as an uphole oriented force against surface  71 . Since D 2  represented by surface  41  is larger than D 3  represented by diameter  49  a net uphole force is increased as pressure PB is increased keeping surfaces  65  and  67  together with increased force. In short, D 2  being larger than D 3  causes increases in pressure PB keep the surfaces  65  and  67  firmly together. The same result is obtained when pressure PA is increased because D 3  is larger than D 1  and PA accesses both dimensions through ports  51  and lower end  31  of tube  29 . 
     To equalize valve  17  before trying to open it, control pressure is raised in control line  23  that shifts the piston  25  against springs  57  and  59  to separate surfaces  65  and  67  so that flow can go through ports  51 , between separated surfaces  57  and  59  and through ports  35  and around the outside of plenum  33  and out lower end connection  15 . 
     Those skilled in the art will appreciate that locating the metal to meal seal inside the housing and having a tortuous path leading to it from opposed directions minimizes the erosive effect of well fluids when the equalizer valve is opened. Additionally the components are configured to keep the valve closed on increasing pressure on either end of the equalizer valve. This is accomplished with just the spaced metal to metal seal and a dynamic seal. A rod piston allows the removal of a third seal in the body as configured in U.S. Pat. No. 9,062,519. The springs  57  and  59  are sized to overcome seal friction in a relatively small rod piston seal assembly as well as seal friction in dynamic seal  43 . 
     The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below: