Subsurface Safety Valves for Gas Storage Wells

Abstract

Gant, Guy W., Member SPE-AIME, Otis Engineering Corporation Abstract Increased value of product, protection of life and personal property have created a demand for downhole safety valves in gas storage wells. Subsurface safety valves have been used for more than 35 years throughout the world in oil and gas producing wells. However, most of these valves were installed in wells producing native hydrocarbons and do not have a predictable pressure decline. The varying predictable pressure decline. The varying pressure in gas storage wells will generally pressure in gas storage wells will generally require a downhole valve that is controlled from the surface if it is to afford maximum protection. Additionally, the valve should protection. Additionally, the valve should permit maximum production with minimum permit maximum production with minimum pressure drop for peak production periods. pressure drop for peak production periods. Therefore, the development of safety valves for gas storage wells was necessary. These valves are controlled from the surface and do not recognize variable flow rates and declining formation pressure. Introduction There are needs for both surface and subsurface safety equipment in the natural gas storage industry. Because of the importance of protecting the product while still in the well and since it is easier to do so - the subsurface safety valve offers maximum protection and will be considered in this paper. The consensus of operating people for the ideal safety valve for gas storage wells will embody the following features:The valve should be designed to permit installing and retrieving by wireline underpressure.Should be controlled from the surface.Permit maximum production rates.Permit injection and withdrawal of product.Have through conduit to permit running pressure surveys, logging instruments, etc. without the necessity of pulling the valve assembly.Must be capable of operating in a dry environment such as experienced in most gas storage wells. (No Lubricant).Should be simple in design - with aminimum number of moving parts.Should be field be repairable.The valve should permit testing when desirable to do so.