Flapper mounted equalizer valve for subsurface safety valves

An equalizing valve for a flapper in a subsurface safety valve has a valve member disposed in a passage in the flapper that is made of a material that changes shape when subjected to a stimulus such as heat, for example. In one configuration, the valve member closes off the passage and in another flow past or through the valve member defines the open position allowing pressure to equalize across the closed flapper. Other valve applications are envisioned for downhole use. The stimulus can come from applied electrical current that causes sufficient heating to have the valve member alter its shape. Mechanical assists to the shape altering can be provided which can also optionally be made of shape changing materials. Biasing into a sealed position is envisioned.

FIELD OF THE INVENTION

The field of the invention is valves where the valve member changes shape defining an open and a closed position and more particularly where the valve is mounted in a flapper, flapper seat or housing of a subsurface safety valve to equalize pressure across the flapper prior to moving it from a closed position with differential pressure across it.

BACKGROUND OF THE INVENTION

Subsurface safety valves are used in wells for emergency shutoff. Typically they are a part of the tubing string and are operated by a hydraulic system at the surface that provides pressure to a control line that runs from the surface to the valve housing. The valve housing connection communicates with an operating piston that is connected to a flow tube. A flapper is biased toward a seat (schematically illustrated as31inFIG. 1) by a torsion spring on the flapper pivot shaft. The movement of the flow tube under pressure delivered through the control line which moves the operating piston connected to it results in pivoting the flapper behind the flow tube. This defines the valve open position. The valve closed position has the flow tube moved up under the force of a spring when pressure in the control line is removed.

When the flapper is closed, a large pressure differential can build up across it. The need to equalize that pressure across the flapper before trying to move the flapper off the seat has been recognized and equalizer valves in the flapper have been in use for some time. One early example of this concept is U.S. Pat. No. 4,478,286. Later examples are U.S. Pat. Nos. 6,644,408 and 7,204,313.

Shape memory alloys (SMA) and materials that assume their original dimensions in response to a stimulus have been used as actuating members to move the ultimate valve member between open and closed positions. Some examples of this design can be seen in U.S. Pat. Nos. 5,199,497; 6,840,257 and 7,055,793.

Prior subsurface safety valve designs mentioned above have used the flow tube to actuate the equalizer valve. There has generally been enough power to do this with operating pistons that are driven hydraulically from the surface through a control line. More recently electrically operated subsurface safety valves are being developed where there are concerns about generating enough force to displace an equalizer valve with the flow tube. The present invention addresses this issue with a valve member made of SMA or another material that can seal a flapper passage in the run in configuration and can be triggered to assume a different shape that allows equalization of pressure. The operation is envisioned to be independent of a flow tube. Some of the designs being developed may not even use a flow tube. These and other aspects of the present invention will be more apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings with the understanding that the claims determine the full scope of the invention.

SUMMARY OF THE INVENTION

An equalizing valve for a flapper in a subsurface safety valve has a valve member disposed in a passage in the flapper that is made of a material that changes shape when subjected to a stimulus such as heat, for example. In one configuration, the valve member closes off the passage and in another flow past or through the valve member defines the open position allowing pressure to equalize across the closed flapper. Other valve applications are envisioned for downhole use. The stimulus can come from applied electrical current that causes sufficient heating to have the valve member alter its shape. Mechanical assists to the shape altering can be provided which can also optionally be made of shape changing materials. Biasing into a sealed position is envisioned.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1is a section through a flapper10showing inlets12and14coming in to the bottom side16. Any number of inlets can be used. Inlets12and14communicate with passage18that terminates at top surface20of flapper10. A cap22has one or more openings24. A valve member26is biased against a seat28by a spring30. An elongated member32secures the valve member26to base surface34. Elongated members36and38connect cap22to valve member26. In theFIG. 1position the members36and38may be in tension or under no net internal force. The spring30pushes the valve member26against seat28while member32is preferably in tension or under no net internal force. Members32,36and38are preferably made of a material that will shorten when subjected to a stimulus S such as magnetically or electrically generated heat shown schematically inFIG. 1. As a result the valve member26is pulled in opposite directions as shown inFIG. 2leaving an annular gap40while pulling the valve member26away from seat28. In the preferred embodiment members36and38can retain their dimension in response to stimulus S while member32shrinks to elongate the valve member26and create passage40to allow equalizing flow42to occur. Valve member can be a resilient material compatible with well conditions and malleable enough to properly deform when subjected to a tensile force delivered from member32. One example may be rubber. Another example is a metal that is ductile and highly elastic. When this happens the spring30is further compressed. When the stimulus S is removed, the parts resume theFIG. 1position.

The preferred embodiment is shown inFIGS. 3-6.FIG. 3is a bottom view of a flapper10′ showing electrical leads44coming toward its center45from the region of the pivot46.FIG. 4is a horizontal view of the flapper10′ showing a passage48going through it.FIG. 5is a close up view of the view ofFIG. 4. Referring toFIG. 5a retainer plate50has one or more holes52and is secured to the flapper10′ by fasteners54. The valve member56accepts the leads44in a manner that transmits heat to the valve member56when power is supplied to leads44. The leads44can extend internally of the valve member56or can be secured to at least some portion of its exterior surface. The valve member56is preferably formed of a shape memory alloy so that it can be inserted into passage48and close it off to differential pressures from the downhole side of the flapper. Preferably, an interference fit on makeup is obtained in passage48. A retainer58allows flow but holds back the valve member56when its dimensions change in response to power applied to leads44. As shown inFIG. 6the valve member56is reduced in diameter and increased in length to allow equalizing flow60to get past it. In essence, the material that changes shape under a stimulus is the valve member.

Those skilled in the art will appreciate that an equalizing valve design for a flapper is operational without contact from a flow tube and can be used in designs that don't even have a flow tube to actuate the flapper. Alternative designs for flapper equalizer valves are presented. In one variation, the valve member is actuated by dimensional changes of an attached component upon delivery of a stimulus to the attached component. That stimulus can be in the form of heat or other types of energy. Heat can be provided from an on board battery linked to wires to generate heat from current where the battery can be wirelessly actuated to power the wires from the surface. The attached members can be shape memory alloys or other shape recovering or altering materials such as magnetic SMAs, piezoelectric materials, magnetostrictive materials, electro adaptive polymers or paraffins. The valve member in that embodiment can be a resilient material such as an elastomer or other materials such as non-elastomeric ductile metals. In the preferred embodiment the valve member itself alters its shape in response to a stimulus and equalizes flow. The design has many downhole applications apart from a flapper equalizer valve and can be used for other valve applications downhole or in control circuits to redirect flow or other applications. The dimension changing member can be a shape memory alloy or one of the selections described above.