Patent Publication Number: US-2017356272-A1

Title: Subsurface injection valve system

Description:
BACKGROUND 
     Hydrocarbon fluids, e.g. oil and natural gas, are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore is drilled, various forms of well completion components may be installed to control and enhance the efficiency of producing fluids from the reservoir. In some applications, an injector well is drilled and used for injection of fluids to facilitate production from a corresponding production well. An injection valve may be deployed with a completion string downhole in the injection well to enable control over the flow of injection fluid. 
     SUMMARY 
     In general, a system and methodology are provided for controlling operation of a subsurface injection valve in a variety of applications. According to an embodiment, the injection valve comprises a flapper which may be selectively shifted to and held in an open position. Depending on the operational configuration of the injection valve, the flapper may be shifted to the open position via fluid flow along a primary flow passage. However, the injection valve also may be shifted to the open position via a separate actuator controllable via pressure applied independently of fluid flow along the primary flow passage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
         FIG. 1  is a schematic illustration of a well system deployed in a wellbore and including an example of a controllable injection valve positioned at a subsurface location, according to an embodiment of the present invention; 
         FIG. 2  is a schematic cross-sectional illustration of an example of the injection valve, according to an embodiment of the present invention; 
         FIG. 3  is a cross-sectional view similar to that of  FIG. 2  but showing the injection valve in a different operational configuration, according to an embodiment of the present invention; 
         FIG. 4  is a schematic cross-sectional illustration of another example of the injection valve, according to an embodiment of the present invention; and 
         FIG. 5  is a cross-sectional view similar to that of  FIG. 4  but showing the injection valve in a different operational configuration, according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
     The disclosure herein generally relates to a system and methodology for controlling fluid flow, e.g. fluid flow during an injection operation. For example, an injection valve may be positioned in a well string deployed in a wellbore to control an injection fluid flow during a subsurface injection application. According to an embodiment, the injection valve comprises a flapper which is pivotably mounted in a valve housing to allow down flow of fluid and to automatically block up flow of fluid along the interior of the well string, e.g. along a primary flow passage of the well string. However, the flapper may be selectively shifted to and held in an open position to facilitate a variety of operations which utilize the interior of the well string. 
     The selective shifting and holding of the flapper in the open flow position may be accomplished via fluid flow along the interior of the well string and through the injection valve. For example, the flapper may be shifted by a flow tube having a restrictor such that sufficient fluid flow along the interior of the well string and through the injection valve causes the flow tube to shift into engagement with the flapper and to hold the flapper in the open flow position. However, the injection valve also may be shifted to the open position via a separate actuator, e.g. piston actuator, controllable via pressure applied independently of fluid flow through the injection valve. 
     In a specific embodiment, the injection valve is a subsurface injection valve which is in a normally closed configuration. In some applications, the subsurface injection valve is deployed along a well string and retrievable to the surface along the interior of the well string. In this and other embodiments, the injection valve combines an ability to shift and hold open the valve via a flow-induced pressure drop across a flow restrictor and an ability to open the valve via adjustment of a differential pressure, e.g. a differential between the primary flow passage and a tubing casing annulus, acting on a separate actuator. The flow restrictor may comprise an orifice, and the orifice may be a fixed or variable orifice disposed along, for example, a flow tube which interacts with a flapper of the injection valve. 
     By using a flow restrictor, e.g. orifice, along a movable member, the injection valve may be shifted to an open flow position without controlling or monitoring a tubing pressure or annulus pressure. The flow restrictor, e.g. orifice, may be sized according to a desired injection flow rate and the flow tube may be sized to cover and protect the flapper when the flapper is shifted to the open flow position. When the injection flow is stopped, the flow tube is automatically moved back to its original position and the flapper automatically closes. 
     In some applications, opening of the injection valve without flow therethrough may be useful. For example, some applications may employ a secondary valve downhole of the injection valve, and the secondary valve may be operated by pressure pulses or other pressure applied through the well string. Thus, it can be useful to open the injection valve for passage of the pressure signal to enable operation of the secondary valve when there is no fluid flowing through the well string. In other words, the separate piston actuator enables selective opening of the flapper without the sufficient fluid flow through the flow restrictor. 
     By way of example, the piston actuator may comprise a piston exposed to internal pressure within the well string or to annulus pressure along the exterior of the well string. The pressure may be used to shift the piston and to thus open the flapper without the sufficient injection flow passing through the flow restrictor of the injection valve. The pressure supplied to actuate the piston actuator also may be provided by other sources, such as an atmospheric chamber or an internal chamber pre-charged with nitrogen or other suitable gas. 
     Depending on the application, the injection valve and components of the injection valve may have various configurations. In some applications, for example, the piston may be in the form of a piston rod although the piston may have other forms, such as a concentric piston disposed around the primary flow passage. In some embodiments, the piston is coupled with the flow tube to move the flow tube although the piston can be coupled directly with the flapper. The piston also can be operated incrementally by, for example, supplying sequential pressure pulses to cycle the piston to different operational positions. By way of example, the piston may be coupled with an indexer, e.g. a J-slot indexer. In this latter example, pressure cycles along the annulus (or along another suitable channel) can be used to shift to the indexer and thus move the piston into various positions with respect to the flapper and/or flow tube. 
     Additionally, the flow restrictor may have various configurations. For example, the flow restrictor may be in the form of a retrievable orifice which can be selectively retrieved to the surface along the interior of the well string. The flow restrictor also may be a fixed size orifice, e.g. a fixed size choke plate, or a variable orifice, e.g. variable Venturi, variable nozzle, flow adjustable orifice, or other type of variable restrictor. 
     Referring generally to  FIG. 1 , an embodiment of a well system  20  for controlling flow of injection fluid is illustrated as positioned in a wellbore  22 . In this embodiment, well system  20  comprises a well string  24  which may comprise a tubing string and may include various types of downhole equipment  26 . The well string  24  and downhole equipment  26  further comprise at least one and sometimes a plurality of injection valves  28 . The injection valve  28  is used to control a flow of injection of fluid along an interior  30  of a well string  24 . The interior  30  forms a primary flow passage for delivering injection fluid downhole. 
     In the example illustrated, the well string  24  and the downhole equipment  26  also comprise at least one secondary valve  32 , e.g. a ball valve, disposed on a downhole side of injection valve  28 . In at least some applications, the secondary valve  32  is actuated via pressure applied along the interior flow passage  30  of well string  24 . As described herein, the injection valve  28  serves to check unwanted flow up through the well string  24 . However, the injection valve  28  also may be selectively shifted and held in an open flow configuration by sufficient down flow of fluid along interior  30  or by actuation of a separate actuator device via, for example, pressure applied independently of fluid flow along interior  30 . The ability to shift and hold the injection valve  28  in an open position independently of fluid flow along interior  30  enables use of pressure pulses through injection valve  28  (or other actuation techniques deployed through injection valve  28 ) to selectively actuate the secondary valve  32 . 
     Additionally, the downhole equipment  26  may comprise at least one packer  34  positioned to enable isolation of a well zone  36  along an annulus  38  disposed between an exterior of well string  24  and a surrounding wellbore wall. In some applications, the well string  24  may be in the form of an injection completion which may be deployed downhole and properly configured prior to isolation of zone  36  and injection of fluid into a surrounding formation  40 . 
     Referring generally to  FIGS. 2 and 3 , schematic cross-sectional illustrations are provided of an example of injection valve  28 . In this example, injection valve  28  comprises a flapper  42  pivotably mounted to a valve housing  44  via a pivot  46 . In a no-flow condition, the flapper  42  is biased to a closed position against a corresponding valve seat  48  via, for example, a spring member  50 . The valve housing  44  may be constructed with a variety of tubular sections coupled together via threaded engagement or other suitable engagement features. 
     Under normal operating conditions, fluid flow in the direction of arrow  52  along interior flow passage  30  causes the flapper  42  to open against the bias of spring member  50 . (As illustrated, interior flow passage  30  extends through the interior of injection valve  28 .) However, the flapper  42  quickly closes, as illustrated in  FIG. 2 , when the fluid flow  52  stops or attempts to reverse. In a variety of injection well applications, the flapper  42  is oriented to open and allow down flow of fluid along interior flow passage  30  while preventing up flow of fluid toward the surface. 
     In various stages of operation, however, it may be desirable to selectively shift and hold the flapper  42  in the open flow position, as illustrated in  FIG. 3 . The injection valve  28  comprises a flow tube  54  movably positioned within valve housing  44  along interior fluid flow passage  30 . The flow tube  54  is selectively movable into engagement with the flapper  42  to shift the flapper  42  to an open flow position and to hold the flapper  42  in this open flow position regardless of the direction of fluid flow along internal flow passage  30 . In  FIG. 3 , the flow tube  54  is illustrated in the engaged position holding flapper  42  in the open flow configuration. By way of example, the flow tube  54  may be constructed with sufficient length to at least substantially cover the flapper  42  and to protect the flapper  42  from fluid flows along interior passage  30  when the flapper  42  is held in the open position. 
     The flow tube  54  may be shifted to the engaged position holding flapper  42  open via fluid flow through a flow restrictor  56  coupled with the flow tube  54 . As discussed above, the flow restrictor  56  may comprise a fixed orifice, variable orifice, or other type of fixed or variable flow restriction. The flow restrictor  56  is configured to restrict fluid flow along interior passage  30  while allowing some fluid flow through an opening  58 . Thus, a sufficient fluid flow along the interior passage  30  of well string  24  and through flow restrictor  56  creates sufficient force to move the flow tube  54  into engagement with flapper  42  until flapper  42  is transitioned to the open flow configuration illustrated in  FIG. 3 . In some applications, the flow restrictor  56  may be in the form of an orifice comprising opening  58 . 
     The flow tube  54  may be biased toward a disengaged position, illustrated in  FIG. 2 , which allows flapper  42  to pivot between open and closed positions. By way of example, a spring member  60 , e.g. a coil spring, may be used to bias the flow tube  54  towards this disengaged position. In the illustrated example, the spring member  60  is positioned between a valve seat housing  62  containing valve seat  48  and an abutment  63  coupled with flow tube  54 . The configuration of flow restrictor  56  and the spring force exerted by spring member  60  may be selected to establish the desired flow of fluid along interior passage  30  that will be sufficient to shift flow tube  54  and flapper  42  to the “held open” configuration illustrated in  FIG. 3 . 
     The injection valve  28  further comprises an independent actuator  64  configured to enable selective actuation of the flapper  42  to the held open configuration independently of fluid flow along interior passage  30 . This allows the flapper  42  to be shifted and held in the open flow configuration even without flow along interior passage  30  in a direction of arrow  52 . By way of example, the independent actuator  64  may comprise a piston actuator  66  having a piston  68  slidably received in a corresponding piston opening  70  formed within valve housing  44 , e.g. within a wall of valve housing  44 . 
     In the example illustrated, piston actuator  66  is coupled with flow tube  54  via a linkage  72 . However, the piston actuator  66  also may be coupled directly with flapper  42 . When sufficient pressure is applied within piston opening  70  on an opposite side of piston  68  relative to linkage  72 , the piston  68  forces the flow tube  54  into the engaged position with respect to flapper  42 , thus holding flapper  42  in the open flow configuration illustrated in  FIG. 3 . The independent actuator  64  thus provides an additional method for selectively shifting and holding flapper  42  in the open flow configuration. 
     Depending on the specifics of a given injection operation, the piston actuator  66  may be configured to expose piston  68  to internal pressure within the well string  24  or to annulus pressure supplied along the annulus  38 . The pressure is supplied to selectively create a pressure differential able to shift the piston  68  and to thus open the flapper  42  without the sufficient injection flow passing through the flow restrictor  56 . In an example, the pressure differential acting on piston  68  may be created by supplying a higher pressure through the annulus  38  compared to the pressure within interior flow passage  30 . 
     It should be noted the actuator  64  may have various configurations. For example, the actuator  64  may be constructed with a single piston or a plurality of pistons in various shapes, sizes and configurations. In some applications, the piston  68  may be in the form of a piston rod, as illustrated in  FIGS. 2 and 3 , although the piston  68  may have other forms, such as a concentric piston disposed around the primary flow passage  30 . The piston  68  also can be operated incrementally by, for example, supplying sequential pressure pulses to cycle the piston  68  to different operational positions. By way of example, the piston  68  can be coupled with an indexer, e.g. a J-slot indexer. When using an indexer, pressure cycles may be supplied along the annulus (or along another suitable channel) to actuate the indexer and to cause corresponding movement of the piston  68 , flow tube  54 , and/or flapper  42  into various positions. 
     Referring generally to  FIGS. 4 and 5 , another embodiment of injection valve  28  is illustrated. In this embodiment, many of the injection valve components are similar or the same as those illustrated in  FIGS. 2 and 3  and are thus labeled with the same reference numerals. However, the pressure for selectively shifting piston  68  is supplied to piston opening  70  from a chamber  74  folding a desired pressurized gas, such as nitrogen. By way of example, the chamber  74  may be formed in a coil  76  charged with nitrogen or another suitable gas to a desired positive pressure. The shifting of piston  68  and flow tube  54  between the free flapper configuration illustrated in  FIG. 4  and the held open configuration illustrated in  FIG. 5  may be achieved by controlling the pressure differential between pressure within interior passage  30  and the pressure within coil  76 . 
     Depending on the application, different types of gases and different configurations of chamber  74  may be utilized for establishing desired pressure differentials able to selectively shift flow tube  54  and flapper  42 . In some applications, for example, the coil  76  may be used for containing atmospheric pressure which establishes a negative pressure. In this type of application, the spring member  50  and/or other spring members are positioned on an opposite side of the piston  68  so as to counteract the negative pressure of the atmospheric trap formed in coil  76 . In this type of configuration, pressure differentials between the interior flow passage  30  and interior of coil  76  can again be used to selectively shift the flow tube  54  and flapper  42 . 
     To accommodate various applications, the number and arrangement of injection valves  28  may vary from one injection well application to another. The injection valve(s)  28  may be utilized in both lateral and vertical wellbores to achieve the desired control over injection fluid flows into surrounding well zones. The injection valve  28  also may be used with many types of completion strings or other well strings to assist in a variety of production operations and/or other types of operations. Similarly, the configuration of each injection valve  28  and the components selected to provide control over the flapper by fluid flow or by pressure may be adjusted according to parameters of the application and/or environment. 
     Although a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Accordingly, such modifications are intended to be included within the scope of this invention as defined in the claims.