Analyzing aquifer driven reservoirs using a computer-oriented approach

Abstract

A new computer-oriented approach for analyzing aquifer driven reservoirs incorporates both geological and historical pressure data to determine original hydrocarbons-in-place and to forecast production. This new approach does not rely entirely on knowledge of the aquifer properties, nor does it depend specifically on a large amount of accurate pressure and production data. Instead, an initial reservoir model, based on the flow properties, boundary conditions, and geometry of the aquifer, is refined by statistically matching the historical pressure data. This is accomplished by applying nonlinear optimization routines to the procedure presented by Fetkovich for calculating water influx. This paper presents the mathematical models for this approach and a detailed discussion of analyzing field data with the new procedure. Analytical models which rely on the properties of the aquifer, and statistical methods which depend entirely on the reservoir pressure history have been previously developed. By incorporating both geological and historical pressure data, the approach presented in this paper provides engineers with a more logical and accurate method for determining original hydrocarbons-in-place and forecasting production from aquifer driven reservoirs. The new computer-oriented technique has been applied successfully to determine the original gas-in-place for 16 gulf coast gas reservoirs, even when no reservoir or aquifer data were available to construct an initial model.