DOWNHOLE HYDRAULIC CONTROL SYSTEM WITH FAILSAFE FEATURES

摘要

A control system for a subsurface safety valve addresses normal open and closed operation and a failsafe operation if key system components fail. It features a single control line (20) from the surface that splits at the subsurface safety valve and goes to one end of two discrete piston chambers (64, 46) that are aligned and isolated from tubing pressure. The piston (36) in one chamber is larger than in the other and the pistons (36, 52) are connected for tandem movement. Each side of the unbalanced system's piston has a seal mounted to it (38, 54) and another for the rod (40, 56) attached to it that exits the chamber. A jumper line (68) connects the chambers (48,62) at a point between the seals in each chamber and features a large reservoir (70). The jumper line (68) is filled with a compressible fluid. Fail safe closure of the valve occurs if any of the four seals fail.