Safety valves are designed to automatically shut in the flow of a well in the event surface controls fail or surface equipment becomes damaged. They are classified according to the location from which they are controlled – surface or subsurface. In this article, subsurface safety valve types, operating systems, working principle, setting depth, and selection process are presented.
It is advisable, and in most cases mandatory, to have a secondary means of closure for all wells capable of natural ﬂow to the surface. The installation on of a sub-surface safety valve (SSSV) will provide this emergency closure capability.
To isolate the tubing, there are two basic types of safety valves:
- Tubing conveyed: Tubing Retrievable Subsurface Safety Valve (TRSV),
- Wireline conveyed: Wireline Retrievable Subsurface Safety Valve (WRSV)