Research and development of low-throttling downhole safety valve for salt-cavern underground gas storages

In order to satisfy the design requirement of the simplified gas injection and brine discharge technology for salt-cavern underground gas storages and reduce the influences of the throttling erosion at downhole safety valves, this paper optimized the sealing mechanisms of the connection in the safety valve and that between safety valve and hydraulic control pipeline according to the principle of maximizing the inner diameter (ID) and minimizing the outer diameter (OD). The new material S13Cr-P110 was applied to the arc valve plate, and the low-throttling downhole safety valve (maximum OD 184.15 mm) for salt-cavern underground gas storages was developed. In addition, pressure test, startup/shutdown function test and leakage rate test were carried out on hydraulic control pipeline and hydraulic control system. It is indicated that SVT5 low-throttling downhole safety valve reduces the throttle at the safety valve by 29.51%, complies with the ANSI/API Spec 14A Equipment Specification of Downhole Safety Valve and is qualified in water seal test and gas seal test. The research results provide the experience for developing the well completion technologies used for gas injection and brine discharge of salt-cavern underground gas storage.