An injection-pressure-operated (IPO) gas lift valve’s closing force is supplied by a nitrogen charge, acting on the effective area of the bellows (Ab), or a spring force. Traditionally, the opening force is the production pressure acting on the area of the port (Ap) plus the injection pressure acting on the bellows effective area minus the area of the port (Ab – Ap). Traditionally, the ratio Ap/Ab is referred to as the R ratio, and has been considered constant for every valve of the same make, model, and port size. The actual R ratio is not a constant and neither is it equal to the published value. The published R ratios are embedded in all gas lift design programs, and are an integral part of the gas lift design process. This paper describes the consequences of using an assumed R ratio in a gas lift design that is not the same as the actual R ratio of the valve that will be installed in the well.
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