中国大气田盖层封气能力综合评价及大气田形成所需盖层条件

Comprehensive Evaluation of Eaprock Sealing Ability and Conditions to Form Effective Caprock for Large Gas Fields in China

通过统计中国45个大气田盖层封闭特征,利用所建立的盖层封气能力综合评价参数对盖层的封气能力进行综合评价,并研究了大气田形成所需的盖层条件。研究发现,中国45个大气田盖层的厚度小于200m,排替压力10～15MPa,气藏压力系数1.0～1.2,盖层封闭能力综合评价参数0.8～1.0,具有较强的盖层封气能力。盖层封气能力综合评价参数与天然气地质储量之间成正比关系,即盖层封气能力综合评价参数越大,气田地质储量越大;反之则越小。大气田形成所需要盖层条件是盖层封气能力综合评价参数大于或等于0.09。

Through statistics of caprock sealing features of forty-five large gas fields in China, comprehensive evaluation parameter of gas-sealing ability of caprock established was utilized to evaluate the sealing ability of caprock and study caprock conditions to form it. The study shows that when caprock thicknessis mainly under 200 rn, displacement pressure mainly between 10-15 MPa, pressure coefficient mainly between 1.0-1.2 and comprehensive evaluation parameter of caprock sealing ability mainly between 0.8-1.0, the coprock sealing ability is excellent. There is direct ratio between comprehensive evaluation parameter of caprock and geologic reserves of natural gas, that is, the larger the comprehensive evaluation parameter and the larger geologic reserves, or vice versa. Condition for effective caprock of large gas fields is that comprehensive evaluation parameter is equal to or greater than 0.09.