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深层异常高压气藏岩石物性随有效覆压变化的幅度比常规气藏大,实测数据表明岩石的压缩系数不是常数,而是随有效覆压而变化（文章发现了符合指数式）,这种变化将影响气藏压降曲线的形状。文章考虑岩石压缩系数随气藏压力的变化,建立了封闭异常高压气藏压降曲线的数学模型。研究表明：异常高压气藏（岩石压缩系数为变量时）,压降曲线为非线性的,曲线主要弯曲点发生在初期,后期接近直线,这说明岩石的压缩及其对气藏压降曲线的影响主要发生在早期。若用气藏初期的生产数据按线性拟合方法外推气藏的地质储量则产生很大的误差,数据较少时误差超过100％。气藏开发过程中,由于储层岩石经历连续的弹性压缩过程,因此压降曲线是连续变化的,但可以简化为两条直线的形式,其误差小于3.27%。该研究对深入了解异常高压气藏的压降特征及预测异常高压气藏的储量及采收率有一定意义

Feature Study of Pressure Fall-off Curves for Deep Gas Reservoirs with Abnorrmal High Pressure

The changing amplitude of rock physical property for gas reservoirs with abnormal high pressure is bigger than that for common gas reservoirs as the effective o-verlain pressure changes. The measured data show the compression factor of rocks is not a constant, but a variable as the effective overlain pressure changes. (The article finds the coincidence exponential equation). This variation will influence the shape of pressure fall-off curves of gas reservoirs. With considering the compression factor of rocks changes as the pressure of gas reservoirs changes,the mathe-matical model of pressure fall-off curves is developed for closing gas reservoirs with abnormal high pressure. The study shows the pressure fall-off curves of gas reservoirs with abnormal high pressure (when the compression factor of rocks is variable) are non-linear. The main bending point of the curves appears at the initial period. The curves are similar with straight lines at late period. It means the compression of rocks and its influence on the pressure fall-off curves of gas reservoirs happens at early period. So,it will produce big error if the production data of the gas reservoir at the initial period are used to extrapolate the geologic reserves of the gas reservoir with the linear fitting method. The error will exceed 100% when the data are few. During the production process of gas reservoirs, the variation of the pressure fall-off curves is continuous since the reservoir rocks experience continuous elastic compression. But the curves can be simplified into the forms of 2 straight lines. The error is less than 3. 27%. The article provides a reference to understand the features of pressure drop of gas reservoirs with abnormal high pressure deeply, and predict the reserves and recovery factor of gas reservoirs with abnormal high pressure.