Abstract: A study was conducted on the determination of water influx in gas reservoir. A new approach was proposed in this paper, which can calculate the water influx directly from the production index curve of gas reservoirs that is easily obtained by production history without assumption of shape and size of water body. Hence, the tediousness and the uncertainty in conventional calculations are avoided by using this method. The calculation indicates its easier, simpler and more practical in use than that established by van Everdingen and Hurst.

Key words: gas reservoir, index curve, water influx, approach