Calculation of the Stabilized Performance Coefficient of Low Permeability Natural Gas Wells

Abstract

Published in Petroleum Transactions, AIME, Volume 216, 1959, pages 240–246. Abstract The direct determination of the stabilized performance behavior of low capacity, slowly stabilizing gas wells is extremely time-consuming and wasteful of gas. From both field experience and theoretical considerations, a test procedure has been evolved by which the stabilized back pressure behavior of such gas wells can be predicted without having to revert to long time flow tests. The method consists of using the isochronal test procedure to establish the slope of the back pressure curve, "n", and the short time variation of the performance coefficient, "C", with time. From this short time transient flow data and theoretical considerations, the value of C at large times can be established. By assuming the radius of drainage of a well to be half the distance between wells, one can calculate the stabilization time for various well spacing patterns. Once the stabilization time for a given spacing has been determined, the value of C can be calculated and the stabilized back-pressure curve can be established. The calculated performance coefficient as a function of time was compared to the experimentally measured values for a number of gas wells. The deviation of the calculated from the experimental results vary depending on the set of short time experimental points used to evaluate the parameters of the equation. The longer the time for the flow test data used in the calculations, the better was the agreement with the experimental results. The time necessary to obtain this data from well tests varies considerably, depending on the physical nature of the reservoir under consideration. Introduction For many years, the U. S. Bureau of Mines Monograph 7 has served as a guide for testing and evaluating the performance of gas wells by means of the back-pressure method.