Abstract:
The present invention provides for a valve to allow injection of fluids into a well or other subterranean facility. The valve comprises a housing and a flow tube assembly disposed in the housing. A restrictor is joined with the flow tube to restrict flow through the flow tube. A seal element also is positioned to selectively prevent production or upward flow of fluids through the valve upon halting injection operations.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention pertains to safety valves used in wells, and particularly to subsurface safety valves used in injection wells or storage facilities related to hydrocarbon production and processing operations. 
     2. Related Art 
     Subsurface safety valves are used in wells to prevent the uncontrolled flow of well fluids to the surface. A typical surface controlled subsurface safety valve has a hydraulic control line that supplies hydraulic pressure to the safety valve. So long as an appropriate level of hydraulic pressure is applied, the valve is held in its open state, allowing flow of fluids through the valve. When the pressure is removed or reduced below the required level, the valve moves to its default closed state, preventing flow of fluids through the valve. 
     Injection wells are typically used to improve production flow in neighboring wells, for storage of hydrocarbons, or for disposal of unwanted byproducts of hydrocarbon production activities (e.g., salt water). By injecting fluids such as water, for example, formation fluids may be displaced into neighboring wellbores so those formation fluids can be recovered. Injection wells may also be used to inject gas or chemicals. It is often desirable to include a safety valve in an injection well to prevent undesired production of fluids when no injection is being performed. 
     SUMMARY 
     The present invention provides for a valve to allow injection of fluids into a well or other subterranean facility, but will close to prevent production or upward flow of fluids through the valve upon halting injection operations. 
     Advantages and other features of the invention will become apparent from the following description, drawings, and claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic view of a valve constructed in accordance with the present invention, shown in its run-in position. 
         FIG. 2  is a schematic view of the valve of  FIG. 1  shown in its open state. 
         FIG. 3  is a schematic view of the valve of  FIG. 1  shown in its closed state. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a valve  10  comprises a housing  12 , a flow tube assembly  14 , and a seal element  16 . 
     Housing  12  has a central passageway  18  and is adapted to join to tubing (not shown) on each of its ends such that the tubing interior and central passageway  18  form a continuous flow path. 
     Flow tube assembly  14  is disposed within housing  12  and comprises a flow tube  20  axially aligned with central passageway  18 . A spring  22  is carried on the outer surface of flow tube  20  and is axially aligned with flow tube  20 , but flow tube  20  is free to move within the coils of spring  22 . An upper end of spring  22  bears on an upper shoulder  24  fixed to an upper end of flow tube  20 , and a lower end of spring  22  bears on a lower shoulder  26  fixed to housing  12  near seal element  16 . 
     Flow tube assembly  14  further comprises a restrictor  28 , sometimes referred to in the art as a “bean” or “orifice”. In the embodiment shown, restrictor  28  is removeably mounted to upper shoulder  24  and preferably has seals  30  to seal against the inner surface of upper shoulder  24 . Restrictor  28  may be variously mounted to upper shoulder  24 . For example, restrictor  28  may engage a profile in the inner surface of upper shoulder  24 , be fixed to upper shoulder  24  by shear pins (not shown), or abuttingly engage the upper end of flow tube  20 . Restrictor  28  may, in an alternative embodiment, be removeably mounted to housing  12 . Restrictor  28  has a flow restriction  32  that limits the volumetric flow rate of fluid through central passageway  18 . Flow restriction  32  may be, for example, an orifice or a narrowed passageway. 
     Seal element  16  is mounted to housing  12  or, alternatively, to lower shoulder  26 . Seal element  16  is preferably a flapper, as shown in  FIG. 1 , but other types of seal elements may be used if appropriate allowances or accommodations are made in valve  10 . In the embodiment shown, seal element  16  is rotatably mounted to lower shoulder  26 . Seal element  26  is biased to move to or remain in its closed state. 
     A lock  34  is movably disposed in housing  12 . Lock  34  is initially placed in an upper position to hold seal element  16  in its open state. In the embodiment shown, lock  34  has a collet  36  that releasably engages an upper profile  38  in housing  12 . Housing  12  also has a lower profile  40  that collet  36  can engage to constrain lock  34  in a lower position. Other retaining devices may be used to secure lock  34  in the upper and lower positions. Lock  34  has an interior passageway so as to not interfere with fluid flow or mechanical intervention through central passageway  18 . Lock  34  may be variously actuated. For example, lock  34  may be actuated using a wireline or coiled tubing conveyed tooling. 
     Valve  10  may also have sensors  42 ,  44 . Sensors  42 ,  44  are shown in  FIG. 1  mounted within the sidewall of housing  12 , but they may also be mounted in the interior region of housing  12  or on the exterior of housing  12 . Sensors  42 ,  44  may be, for example, pressure or temperature gauges. Sensors  42  are preferably located above restrictor  28  and sensors  44  are preferably located below restrictor  28 , meaning the measurements taken are from those respective regions. Sensors  42 ,  44  can take measurements from areas both inside and outside of housing  12  (i.e., tubing and annulus readings). 
     In operation, valve  10  is joined to tubing and run into a well in the configuration shown in  FIG. 1 . Lock  34  holds seal element  16  in its open state so well fluids can pass freely through valve  10  as it descends into the well. 
       FIG. 2  shows valve  10  when fluid is being injected into the well. Injected fluid is pumped through the tubing and enters restrictor  28  from above. Restrictor  28  creates a pressure differential across flow restriction  32 . The pressure differential causes restrictor  28  to move downward, pushing flow tube  20  downward and thereby pushing lock  34  downward as well. Spring  22  is compressed as restrictor  28  moves downward. Upon sufficient travel, lock  34  moves clear of seal element  16  and collet  36  engages lower profile  40 . Seal element  16  is held in its open state by flow tube  20 . 
     When injection operations cease, the pressure differential driving restrictor  28  to its lower position dissipates. As shown in  FIG. 3 , spring  22  returns to its natural or initial length, pushing flow tube  20  clear of seal element  16 . Seal element  16  moves to its closed state, thereby blocking fluid flow upward through valve  10 . 
     Because injection fluids are generally pumped through central passageway  18  at high velocities, flow restriction  32  may experience wear and change in size over time, reducing the differential pressure across flow restriction  32 . If the differential pressure is lessened, then the driving force on restrictor  28  is also lessened. A change in injection requirements may also motivate replacement of restrictor  28 . Restrictor  28  can be removed and replaced to maintain valve  10  in working order using conventional intervention methods such as through-tubing intervention. 
     Operation of valve  10  does not require the use of hydraulic control lines, though such lines could be run for other purposes, if desired. Also, electrical control lines or conduits may be used to communicate electrical signals to and from the surface. Use of such control lines or conduits would allow, for example, monitoring of well conditions and the operational status of valve  10 . 
     Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.