对容积法计算气藏采收率和可采储量的修正

CORRECTION OF THE GAS RESERVOIR RECOVERY FACTOR AND RECOVERABLE RESERVES ESTIMATED BY VOLUMETRIC METHOD

通常在应用容积法计算气藏采收率和可采储量时 ,一方面 ,未考虑到容积法探明地质储量存在一定误差及其没有完全反映气藏中天然气的可流动性 ,误把动态储量采收率当作容积法地质储量采收率 ,导致计算的可采储量偏大 ;另一方面 ,忽视了水驱气藏原始和废弃条件下的含气饱和度的差异。从而导致公式应用的错误和计算结果的失真。文章以理论分析结合实例计算 ,提出了气藏动态储量与动态法采收率才是一一对应的逻辑匹配关系 ,由两者计算的可采储量是合理、正确的 ;而容积法储量采收率应根据动态储量采收率及动态储量与容积法储量之比例来折算。动态储量采收率具备横向可比性 ,容积法储量采收率则不然。同时 ,提出对于水驱气藏应考虑原始与废弃时含气饱和度的差异 。

In general, when the gas reservoir recovery factor and recoverable reserves were estimated by volumetric method, on the one hand, a certain error existing in the proved geological reserves estimated by volumetric method wasn't considered and the recovery factor calculated by dynamic reserves was wrongly taken as that by the volumetric geological reserves, because of neglecting the flowability of natural gas in reservoir, which led to that the recoverable reserves estimated was on the large side, and on the other hand, it was neglected that the gas saturation under initial conditions was different from the one under abandonment conditions in a water-drive gas reservoir. It is the reason why the formula was wrongly applied and the result calculated was far from fidelity. Through theoretical analysis and example calculation, it is thought that only the dynamic reserves can be logically related to the dynamic recovery factor, the recoverable reserves calculated by the two parameters are reasonable and correct and the recovery factor calculated by volumetric reserves should be reduced according to the recovery factor calculated by dynamic reserves and the dynamic reserves-volumetric reserves ratio. The recovery factor calculated by dynamic reserves has lateral comparability but that by volumetric reserves hasn't. Meanwhile, it is proposed that the difference between the gas saturation at the initial stage and that at the abandonment pressure stage should be considered, thus further correcting the methods of calculating gas reservoir recovery factor and recoverable reserves by volumetric method.