The variable-gradient design-line method is a widely accepted procedure for spacing gas-lift valves (GLV's) in a continuous-flow gas-lift (GL) installation. Injection-pressure-operated (IPO) and production-pressure-operated (PRO) GLV's can be used in a variable gradient designed installation. The primary purpose of GLV's is to unload a well to the desired depth of gas injection. If the installation design is based on a constant surface injection-gas pressure (pio), the GLV's must be opened by an increase in the flowing-production pressure at valve depth (ppfD) rather than an increase in injection-gas pressure at valve depth (pioD)· PPO, also called fluid-operated, valves are opened and closed by changes in ppfD.

This paper outlines in detail the calculations for a variable-gradient continuous-flow installation design procedure based on a constant pio for spacing the unloading PPO valves. The valve spacing and port size selection includes performance characteristics of PPO GLV's. A simplified method for calculating the injection daily volumetric gas rate (qgSC) throughput of an unbalanced bellows type of PPO valve on the basis of a change in and the valve bellows-assembly load rate (BIr) is given in the  Appendix.

Keywords:
pptd, installation design, glv, production rate, performance curve, psig, artificial lift system, ppo valve, gas injection, upstream oil & gas
Subjects:
Artificial Lift Systems, Well & Reservoir Surveillance and Monitoring, Gas lift
Copyright 1995, Society of Petroleum Engineers
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