孤岛浅层气藏的盖层评价与成因机制

CAP ASSESSMENT AND GENETIC MECHANISM OF ISOLATED ISLAND SHALLOW GAS POOLS

李学田 戴贤忠 张文达 肖无然

Li Xuetian Dai Xianzhong Zhang Wenda Xiao Wuyan

胜利油田地质科学研究院 2. 地质矿产部石油地质中心实验室 无锡

Institute of Geoscience, Shengli Oil Field 2. Central Laboratory of Petroleum Geology, MGMR

孤岛气藏是一种浅层的低压气藏,其盖层泥岩的孔隙度都大于6%。本文利用压汞—气体吸附法分析获得突破压力、中值半径、微孔半径分布类型、封盖饱和度、气柱高度、遮盖系数等特征参数。结合济阳拗陷气田地质特征,对孤岛浅层气藏的盖层作出了定量评价;讨论了盖层效应。指出由于盖层的存在,必然产生储量的富集系数、天然气组分的含量和气层的压力系数等规律性的变化;利用盖层特征参数对孤岛浅层气藏的形成和保存的成因机制进行了分析。提出了气藏的原始地层压力、含气饱和度、弹性产率等与盖层的突破压力、遮盖系数、气柱高度等存在着极好的相关性。

Isolated island gas pool is a kind of shallow gas pools with low pressure, and the porosity of its capping mudstone bed all exceeds 6%. Using mercury injection-gas absorption method, several characteristic parameters have been obtained: the distributive patterns of abrupt pressure, mean radius and micropore radius,and the saturation under the capping bed, the gas column height, and shielding factor. Combined with geological characteristics of gas field in Jiyang depression, the capping bed of isolated island shallow gas pools are quantitatively evaluated. The effects of capping bed are discussed, proposing that there must be certain regular changes in the enrichment coeficient of reserves, the contents of natural gas components and the pressure coeficient of gas reservoir due to the existence of capping bed. With the application of characteristic parameters for capping bed, the formative preserving mechanisms for isolated island shallow gas pools are analysed, suggesting good correlations of the initial formation pressure, gas bearing saturation and elastic yields with abrupt pressure, shielding factor, gas column height of the capping bed.

https://doi.org/10.11781/sysydz199003307