异常高压凝析气藏物质平衡方程推导

物质平衡方程可在早期计算气藏的储量以及预测气藏的生产动态,而异常高压凝析气藏则是一种极其特殊的气藏类型,在其气体开采过程中,随着地层压力的不断下降,地层中会发生反凝析现象,形成气、液两相,而且储层孔隙及地层水的压缩系数随压力的改变变化也很大。因此异常高压凝析气藏的物质平衡方程与常规气藏的物质平衡方程存在着较大的差异。为此,基于摩尔量守恒的原理,推导了异常高压凝析气藏的物质平衡方程通式,描述了气藏弹性能的释放过程、岩石颗粒的弹性膨胀作用以及地层束缚水的弹性膨胀作用,并将该方法运用于某实际异常高压凝析气藏中,从储量计算的结果来看,与实际情况较为吻合,从而验证了该方法的准确性。

Deduction of the material balance equation of abnormal high pressure gas condensate reservoirs

The material balance equation can be used to calculate the reserves of gas reservoirs and forecast the production performance of a gas reservoir in the early stage. However, an abnormal high pressure gas condensate reservoir is very typical, and during its gas extraction, the phenomenon of retrograde condensation will occur with the strata pressure decreasing gradually and the two phases of gas liquid will be formed. In addition, the reservoir pore and the formation water compressibility coefficient will change sharply along with the decrease of the formation pressure. All these characteristics will result in a big difference in the material balance equations between an abnormal high pressure gas condensate reservoir and a conventional one. Based on the principle of Molar amount conservation, the material balance equation for an abnormal high pressure gas condensate reservoir is deduced. Besides, the release process of the elastic energy of gas reservoirs, the effects of the elastic expansions of rock particles and the bound water in the strata are also presented. The result of an application of the equation in a practical abnormal high pressure gas condensate reservoir matches the on site conditions, which validates its accuracy.