渝东南复杂构造区常压页岩气富集机理与评价指标

Enrichment mechanism and evaluation indicators of normal pressure shale gas in the complex structural area of southeastern Chongqing

房大志

FANG Dazhi

中国石化 重庆页岩气有限公司, 重庆 408400

SINOPEC Chongqing Shale Gas Co., Ltd., Chongqing 408400, China

渝东南复杂构造区常压页岩气广泛分布，资源勘探前景良好，常压页岩气逐渐成为页岩气勘探开发热点领域。该区受多期构造演化作用影响，页岩气保存条件差异较大，页岩储层及气体地球化学特征在不同压力体系下呈现出差异性分布。研究区页岩气烷烃同位素整体上呈现出自盆地边缘向盆外逐渐变重、干燥系数逐渐降低的趋势，指示不同构造区气体保存与逸散情况存在差异。较轻的烷烃气碳同位素和较高的干燥系数指示了更好的页岩气保存条件。综合对比渝东南复杂构造区下志留统龙马溪组页岩气评价的各项指标，发现孔隙度、面孔率、变形指数、含气性等地质静态指标在向斜构造中表现出强非均质性，单井页岩样品间差异显著；烷烃碳同位素、干燥系数、产气量等地质动态指标在不同构造区差异明显。综合页岩储层及气体地球化学特征参数进行评价，平桥、东胜背斜构造区气体保存条件良好，是页岩有利储层及页岩气富集甜点区。

Normal pressure shale gas is widely distributed in the complex structural area of southeastern Chongqing, with good prospects for resource exploration. Normal pressure shale gas has gradually become a hot topic in shale gas exploration and development. Due to the influence of multiple stages of structural evolution, there are significant differences in the preservation conditions of shale gas in the complex structural area of southeastern Chongqing. Shale reservoirs and gas geochemical characteristics are distributed differently under different pressure systems. The overall trend of alkane isotopes in shale gas in the study area shows a gradual increase in weight from the basin margin toward the basin exterior, while the dryness coefficient gradually decreases, indicating differences in gas preservation and dissipation in different structural zones. Lighter alkane carbon isotopic values and a higher dryness coefficient indicate better shale gas preservation conditions. A comprehensive comparison of shale gas evaluation indicators from the Lower Silurian Longmaxi Formation in the complex structural area of southeastern Chongqing reveals that static geological parameters including porosity, face porosity, deformation index, and gas content exhibit strong heterogeneity within synclinal structures, with significant variations among shale samples from individual wells. Meanwhile, dynamic geological parameters such as alkane carbon isotopes, dryness coefficient, and gas production rate show marked differences across various structural zones. An integrated evaluation of shale reservoir properties and gas geochemical characteristics demonstrates that the Pingqiao and Dongsheng anticline zones exhibited favorable gas preservation conditions, representing optimal shale reservoirs and sweet spots for shale gas enrichment.

中石化科技部项目“渝东南地区浅层页岩气勘探开发关键技术” P24115

https://doi.org/10.11781/sysydz2025040720