Evaluation Of Water Storage Gas Reserves

According to whether the reservoir has water intrusion or not, it can be divided into water drive gas reservoir and closed gas reservoir. Gas development experience shows that: most of our country’s gas reservoirs are water drive gas reservoir with different level of activity of water body. Therefore, making deep study to water drive gas reservoir has important theoretical and practical value. The reserve volume of natural gas is the material basis to develop program, facilities design, reserve estimate and dynamic research. For the water drive gas reservoir, as it involves the impact of water invasion, the reliability of the reserve results is closely related to the accuracy of the calculation of water influx. However, the accurate calculation of water influx is still a difficult problem to solve.This paper, on the basis of extensive literature research and previous studies, do research on calculation of reserve of water drive gas reservoir and water influx, and calculation of dynamic reserve of single well. As the material balance method is the most commonly used method of reserve estimate of water drive gas reservoir, this article firstly analyzes the conventional application of the material balance equation. Also, the dynamic reserve calculation of single well needs the data of bottom hole pressure, the paper analyzes the common method to calculate bottom hole pressure. On the basis of the foregoing, we propose the use of robust genetic algorithm to do nonlinear fitting and optimization to production performance data, find method of calculation of reserve of water drive gas reservoir and water influx. In the aspect of calculation of dynamic reserve of single well, in view of gas well that produces water exist gas and water two-phase fluid flow, we establish the deliverability equation of water yield gas well with unstable flow. Using material balance equation to compute the average water saturation, contact to relative permeability curve, establish objective function for production history matching, then compute dynamic reserve of single well, gas well pressure and water saturation variation.