Predicting the initial reserve and the performance of high pressure gas reservoirs

A challenging problem confronting reservoir engineers these days is the estimation of the initial gas in-place and prediction of the performance of high pressure gas reservoirs because of the effect of formation compressibility and possible water influx from small associated aquifer or embedded shales. Several material balance models have been proposed to estimate the initial gas in-place and predict the prevailing production mechanisms for such reservoirs. However, most of these models have prier assumption about either the formation compressibility or the aquifer size. This paper presents a material balance solution plot. The solution includes gas expansion, reservoir condensate expansion, rock expansion, formation water expansion, water influx from associated aquifer, water influx from embedded shales, and gas evolved from formation water. Application of the material balance solution plot described in this paper shows that this solution plot successfully estimate the initial gas in-place and predict the prevailing reservoir production mechanism. Comparison of the new solution explained in this paper with the others shows that the new solution is more simple and accurate than the others.