储层孔隙度是容积法储量计算的基本参数，而准确确定地层条件下的孔隙度值是提高储量计算精度的基础。根据异常高压气藏岩心应力敏感性实验得到的孔隙度值变化的不可逆性，提出了孔隙度随有效覆压变化史的模型，进而提出了在地层原始条件下计算孔隙度的2种方法——实验曲线法和修正系数法。以磨溪气田嘉二气藏为例的岩心实验及研究表明：覆压孔隙度φ_f与常规孔隙度φ₀的比值平均为0.846(可采储层)，覆压孔隙度φ_f与原始地层条件下孔隙度φ_i平均误差57%；常规孔隙度φ₀与原始地层条件下孔隙度φ_i平均误差11.49%；岩样基础孔隙度越低，误差越大，因此有必要对常规孔隙度及覆压孔隙度进行修正。建议使用经过修正得到的原始地层条件下的孔隙度与测井解释孔隙度相结合，制作孔隙度的解释图版，来用于容积法储量计算。

Since Porosity is a basic parameter for the calculation of gas reservoir reserves, determining the porosity under the reservoir condition is the only way to enhance the precision of the calculation. Based on the measurement of the porosity changes with effective stress and the irreversibility of porosity changes with stress, this paper proposes a conceptual model of porosity change history with the confining pressure. Through the study, two methods to calculate the in-situ porosity value are set up. According to the experimental data of core samples from Jia-2 gas reservoir of Moxi Gasfield, the ratio of conventional confining porosity φ_f to core analysis porosity φ₀ is 0.846 (average). The error of confining porosity φ_f with in-situ porosity φ₀ is 5.7%. The error of conventional porosity φ₀ with in-situ porosity can reach 11.5%,It is suggested that it is necessary to modify the porosity and connect it with the logging porosity to make interpretation charts for the reservoir reserve calculation. 