Production Decline Type Curves for Gas Wells Producing Under Pseudo-Steady-State Conditions

Abstract

ABSTRACT Predicting the production rates from a given gas well is of considerable interest in the natural gas industry. The conventional method to predict the performance of the gas reservoirs require a number of data which are often unavailable. This is especially true for low permeability reservoirs. In many cases, the production data is the only available information on the gas wells. In such cases, the production decline type curves have been utilized to predict the future production rate based upon the past production data. However, the published type curves have been generated with certain assumption(s) which limit their applications. These assumptions include consideration of only Darcy flow, use of constant gas viscosity and deviation factor, as well as ignoring the skin factor. This paper presents a set of new production type curves for gas wells (production forecasting) without any of the above mentioned assumptions. The type curves are generated by utilizing a simple reservoir model which accounts for variations in gas deviation factor and viscosity as well as non-Darcy flow. The results of this study are presented in the form of dimensionless rate-time and cumulative production-time type curves. The type curves presented in this study can be utilized to estimate the reserves and forecast future production of a given gas well. In addition, the application of the developed type curves was found to be significantly easier than those previously published. Finally, the developed type curves were verified using actual production data obtained from the gas wells in the Appalachian Basin.