Patent Application
20060162932
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.
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.
Referring to
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
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
In operation, valve 10 is joined to tubing and run into a well in the configuration shown in
When injection operations cease, the pressure differential driving restrictor 28 to its lower position dissipates. As shown in
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.
