川东地区中二叠世茅口组台-槽分异演化及常规-非常规天然气勘探有利区新发现

Platform-trough differential evolution and recent findings on conventional and unconventional natural gas play fairways in the Middle Permian Maokou Formation， eastern Sichuan Basin

郭杰 肖笛 罗冰 张本健 陈骁 张玺华 李明隆 谭秀成

Jie GUO Di XIAO Bing LUO Benjian ZHANG Xiao CHEN Xihua ZHANG Minglong LI Xiucheng TAN

四川盆地二叠纪裂陷演化过程、沉积充填规律不清，制约了油气勘探。基于露头、最新钻测井和地震资料，划分了川东地区二叠系茅口组层序，研究了地层沉积充填过程。研究表明：裂陷活动从中二叠世早-中期开始，茅（茅口组）一段沉积晚期开始进入初始裂陷期；茅二段沉积早期15和16基底断裂活化明显加剧，受南北向拉张应力的影响，研究区变为“南台地、北裂陷”沉积地貌特征；茅二段沉积晚期以后构造活动进一步加强，研究区进入裂陷持续发育期。多期构造-沉积分异过程很可能受峨眉山大火成岩省幕式活动影响，形成多期、多个坡折带。石柱、成20井区和张12井区的孤峰段为碳酸盐岩台地内相对低洼区域沉积，内部富有机质，高能滩区与周缘低洼区域孤峰段烃源岩形成良好的源-储配置，有望形成规模勘探区。成23井—忠县台缘浅滩带是天然气有利勘探区。

The unclear understanding of the Permian rifting evolution and sedimentary filling patterns in the Sichuan Basin has hindered hydrocarbon exploration in this region. Based on outcrop observations and the latest drilling， logging， and seismic data， we determine the sequences in the Maokou Formation within the eastern Sichuan Basin and investigate the formation filling process from deposition. The results indicate that rifting in the eastern Sichuan Basin began in the early to middle Middle Permian， as manifested by the initial rifting stage during the late depositional stage of the 1st member of the Maokou Formation （also referred to as the Mao 1 Member）， and the significantly intensified activation of Nos. 15 and 16 basement faults during the early depositional stage of the Mao 2 Member. In response to the tensile stress in the N-S direction， the sedimentary landscapes of study area are transformed as characterized by southern platforms and northern rifts. Following the late depositional stage of the Mao 2 Member， the tectonic activity got further intensified in the study area， evolving into a period of continuous rifting development. This multi-stage tectonic and sedimentary differentiation is likely influenced by the episodic activities of the Emeishan large igneous province （ELIP）， leading to the formation of multi-stage slope break zones. The Gufeng Member of the Maokou Formation in the Shizhu area， as well as the Cheng-20 and Zhang-12 well blocks， represents organic matter-rich deposits formed in low-lying areas of the carbonate platform. Meanwhile， the reservoirs of the high-energy shoal facies and the source rocks of the Gufeng Member in the low-lying areas create a favorable source rock-reservoir configuration. All these establish the areas as potential large-scale exploration region. Furthermore， the platform-margin shoal zone in well Cheng-23—Zhongxian County is identified as a natural gas play fairway.

10.11743/ogg20250114