砂泥岩地层古天然气扩散系数恢复方法及其应用

Restitution method for palaeo-gas dispersion coefficient in sand shale formation and its application

为了建立一套砂泥岩地层古天然气扩散系数的恢复方法,通过实验测试泥岩天然气扩散系数,并对其进行地层条件下的校正。由泥岩天然气扩散系数计算求取砂岩天然气扩散系数。利用地层中砂泥岩天然气扩散系数和砂泥岩在地层中的相对发育程度求取地层天然气扩散系数。在古埋深恢复的基础上,通过求取地层中砂泥岩的古孔隙度,对其砂泥岩古天然气扩散系数进行恢复,在此基础上利用地层中砂泥岩古天然气扩散系数和砂泥岩的相对发育程度,建立了地层古天然气扩散系数的恢复方法。将其应用于松辽盆地昌德气藏泉一、二段盖层古天然气扩散系数的恢复研究中,得到泉一、二段盖层古天然气扩散系数随地质时期演化逐渐减小的结果,符合压实成岩演化规律,表明该方法用于砂泥岩地层古天然气扩散系数恢复是可行的。

One restitution method for palaeo - gas dispersion coefficient in sand shale formation is needed. So, based on experiments the gas dispersion coefficient of gas in shale is measured and corrected according to formation conditions. The gas dispersion coefficient in sandstone can be obtained according to that in shale. The gas dispersion coefficient in formation can be obtained according to the gas dispersion coefficient in sand shale formation and the relative growth degree of sand shale in formation. With the application of palaeo - buried depth restitution, the palaeo - gas dispersion coefficient in sand shale is obtained based on the calculation of palaeo - porosity in sand shale. According to palaeo - gas dispersion coefficient in sand shale and the relative growth degree of sand shale, the palaeo - gas dispersion coefficient restitution method for sand shale is established. This method has been applied to the research on palaeo - gas dispersion coefficient restitution for Member QuanI and Member QuanlI cap rocks in Changde gas reservoir in Songliao basin. The research results suggest that in Member QuanI and Member QuanII cap rocks the palaeo - gas coefficient decreases with geologic time, which is coincident with the diagenetic evolution rules of compaction. According to the research, it is fea- sible to use this method to palaeo- gas dispersion coefficient restitution in sand shale.