地质储量和水侵量是确定气藏开发规模及开发设计的重要参数。传统的视地层压力识别法是判别 气藏驱动类型的常用方法，但对于柴达木盆地涩北气田水驱作用不强的气藏，其早期的压降曲线为一条 直线，容易被误判为定容无水驱气藏，所计算的储量要比采用水驱气藏计算出的储量高。以涩北二号 气田A 气藏为例，应用视地质储量法，在不需要知道水侵量大小的情况下直接应用生产动态数据，绘制出 气藏视地质储量变化曲线，这样就可以计算出地质储量，再把计算得到的地质储量代入视地质储量计算 公式即可反求出水侵量的大小。该方法简便、实用，对指导气田的后期开发具有借鉴作用。

Original gas in place（OGIP） and water influx are the key parameters to determinate development strategy and production scheme for a gas reservoir. Traditional apparent formation pressure is common process for judging gas reservoir drive mechanism. However for those gas reservoirs weakly affected bywater drive, its pressure drop curve is a straight line in early period, easily to be misinterpreted as elastic energy driving, and its OGIP calculation results are also greater than using geologic reserve calculation method with water drive. TakingA gas reservoir in Sebei No. 2 gas field as an example, this paper applied apparent geologic reserves method under the situation of unknown water influx to estimate OGIP from mapping apparent geological reserve curves, and then backward calculated water influx by putting OGIP data into the equation. This calculation method is proved to be an effective approach for Sebei Gas Filed. Simultaneously, it also has positivemeaning to guiding the gas field development during the later period.