Reciprocal productivity index [RPI] for oil well and gas well evaluation. Anon. JPT, December 1997, 49(12), 1349, 1350. (Synopsis SPE paper 37409).

Details are presented of the RPI. Its application enables descriptive engineering parameters, such as permeability to be estimated, and the generation of production forecasts. Ultimate recovery on the basis of these parameters without the cost of full numerical simulation or extended build-up tasks is provided by the RPI graphical production-analysis method. The method's theoretical basis being that the traditional constant rate on-pressure boundary conditions are sufficient, but the necessary boundary condition only requires the outflow-face transmissibility to remain constant over time. Hence, accurate production histories can be evaluated by traditional well-testing methods when both the rate and producing pressure are varying with time. Two examples are presented of the RPI interpretation procedure.