| 摘要 |
The invention relates to a control system for a subsurface safety valve (SSV). A pressure-balance feature is introduced such that the control system components are unaffected by the depth of placement of the SSV. Through the use of this feature, the standard hydraulic control system used for surface components can also be used for an SSV regardless of its depth of installation. In another feature of the invention, a shuttle valve is provided so that each time the SSV is stroked, a volume of control fluid is purged into the annulus. One embodiment of the shuttle valve may or may not be sensitive to annulus pressure and employs annulus pressure as an aid to stroking the shuttle valve upon application of surface control pressure to assist in actuation of the SSV, while at the same time providing for a purge of a controlled volume of fluid.
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