New material balance analysis method for abnormally high-pressured gas-hydrocarbon reservoir with water influx

Because of the strong stress sensitivity in abnormally high-pressure gas-hydrocarbon reservoirs, the calculation of aquifer volume is very difficult; it is hard to analyze the material balance equation (MBE) for the abnormally high pressured gas-hydrocarbon reservoirs with water influx. The traditional MBE is poorly reliable. Because the volume of the aquifer is corresponding to the dynamic reserves, the accuracy of aquifer volume calculation will be decisive to the reliability of material balance analysis. Therefore, the research of a new MBE method has been conducted to the abnormally high pressured gas-hydrocarbon reservoirs with water influx. This paper proposed a new concept to describe the rock elastic energy and water influx energy using the linear relationship of cumulative production, which simplifies the MBE and converts to a multivariate nonlinear equations. The equations were solved by iteration method. Furthermore, the water influx energy, water influx, and aquifer volume can be calculated by the linear relation coefficient of cumulative production. This method is adopted for calculating the results of several scenarios of numerical simulation and actual production data in a certain abnormally high pressured gas-hydrocarbon reservoir. The accuracy of the new method for calculating the dynamic reserves and drive index is validated. This method also avoids the error caused by calculating water influx energy or neglecting the rock elastic energy in abnormally high pressured gas-hydrocarbon reservoirs.