Gas Well Decline Analysis Under Constant-Pressure Conditions, Wellbore Storage, Damage, and Non-Darcy Flow Effects

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper presents a simple and accurate method to determine all the reservoir parameters for transient constantpressure drawdown data of gas wells influenced by wellbore storage, formation damage, and high-velocity flow effects. The working equations are written in such a way that allows a graphical analysis of the measured variable rate with time that is very much similar to the analysis of constant-rate production case. No iterative procedure, multi-rate test, nor non-linear regression is necessitated to determine the formation damage and the non-Darcy flow effects. The well test data analysis requires two plots to directly obtain all the parameters of interest. The formation permeability and the non-Darcy flow coefficient are obtained from the first plot, whereas the skin factor is obtained from the second analysis plot.This work systematically illustrates the applicability of the derived equations using several simulated examples. The final working equations are written in various forms, which allows the well test analyst to select the form that is most convenient for his application. The advantages of the proposed method are clearly shown when the analysis procedure and results are compared to other analysis techniques.