Accurate estimation of the initial gas in-place for high-pressure gas reservoirs is quite often difficult because of the effect of formation compressibility and the uncertain presence of water influx from small, associated aquifer or adjacent shales.

This paper presents a material balance solution for estimating the initial gas in-place and predicting the prevailing production mechanism for high-pressure gas reservoirs. The material balance solution incorporates water influx from aquifer, water influx from shale, formation expansion, connate water expansion, and formation of condensate. Application of the proposed solution to four case histories of high-pressure gas reservoirs shows that this solution would successfully estimate the IGIP after production of 15% of the initial gas in-place and predict the prevailing reservoir production mechanism. In comparison with the available methods, the proposed solution requires no prior assumptions about the formation compressibility, aquifer size, or volume of adjacent shales.

You can access this article if you purchase or spend a download.