Balanced line tubing retrievable safety valve

摘要

A tubing retrievable surface controlled subsurface safety valve 106 is adapted to be positioned in a well tubing string 102 to control the flow through the tubing string. The safety valve includes an annular housing or body 200 defining a fluid passageway through which fluids and/or gasses may flow to the surface. The safety valve is equipped with a valve closure member such as flapper 252, positioned in the fluid passageway which is moveable between an open and closed position. The valve closure member is engaged and actuated by a longitudinally extending operator 242 that engages the valve closure member 252. In one embodiment, the longitudinally extending operator 242 may be a tubular member longitudinally moveable within the valve body. The longitudinally extending member 242 is operatively coupled to a spring guide 226. A biasing spring 222 is positioned in a spring chamber 120 defined by a spring housing 228 and the spring guide 226. A spring 256 biases the closure member 252 in the closed position. A balance line 114 extending from the surface is connected to a balance pressure conduit 118 that is in fluid communication with the spring chamber 120 to balance the hydrostatic pressure from the control line 112. The spring chamber 120 is isolated from well pressure at the top and bottom therefore the pressure applied to the spring chamber 120 through the balance pressure line via the balance pressure conduit 118 counteracts the hydrostatic head of the fluid in the control line or lines, thereby enabling the subsurface safety valve 106 to operate at vary depths.