川东地区中二叠统茅口组二段上亚段台缘带沉积演化特征及勘探潜力

Sedimentary evolution and hydrocarbon exploration potential of platform-margin zones in the upper sub-member of the 2 member of the Middle Permian Maokou Formation， eastern Sichuan Basin

牟月 谭秀成 罗冰 李明隆 徐发波 易娟子 吴永宏 杨文杰 郭杰 肖笛

Yue MU Xiucheng TAN Bing LUO Minglong LI Fabo XU Juanzi YI Yonghong WU Wenjie YANG Jie GUO Di XIAO

四川盆地茅口组二段上亚段（茅二上亚段）台缘带勘探潜力巨大，近年来在川中—川西北地区不断取得突破，但川东地区研究相对薄弱，台缘带展布特征尚不清晰。在川东地区开展小层划分对比的基础上，研究了台缘滩展布和演化规律，并提出有利油气勘探区带。结果表明：①茅二上亚段在岩性组合和测井上具有2期四级旋回，据此划分出2个小层。1小层和2小层均为镶边碳酸盐岩台地沉积体系，主要发育台缘滩、滩间潟湖、台内滩和半局限海亚相。②1小层和2小层台缘带展布特征相似，邻水—丰都和大竹—忠县两带台缘滩均呈北西-南东向展布。1小层两带台缘滩分异显著，被带状滩间潟湖分隔；2小层台缘滩侧向迁移，平面分布面积扩大，两带滩体在东部连片发育。③台缘滩体叠合准同生期岩溶和白云石化作用是优质储层发育的主要原因。邻水—丰都和大竹—忠县台缘滩带是有利储集层发育区，斜坡-海槽和滩间潟湖是烃源岩发育的有利区。大竹—忠县台缘滩油气勘探潜力大，是新的油气勘探有利区域。

Platform-margin zones in the upper sub-member of the 2 member of the Maokou Formation （also referred to as the Mao 2 Member） in the Sichuan Basin exhibit enormous hydrocarbon exploration potential， with constant breakthroughs having been made in the central to northwestern Sichuan Basin. However， the distribution pattern of platform-margin zones in the eastern Sichuan Basin remains unclear due to limited studies. Focusing on the eastern Sichuan Basin， we conduct sub-layer division and correlation， investigate the distribution and evolutionary pattern of the platform-margin zones therein， and propose hydrocarbon play fairways. The results indicate that the upper sub-member of the Mao 2 Member in the eastern Sichuan Basin exhibits two fourth-order eustatic cycles， as evidenced by lithologic assemblages and logs. Based on this finding， the upper sub-member can be divided into sub-layers 1 and 2. Both sub-layers consist of the sedimentary systems of rimmed carbonate platform facies， with major sedimentary subfacies including platform-margin shoals， inter-shoal lagoons， intra-platform shoals， and semi-restricted seas. The platform-margin zones in both sub-layers show similar distribution patterns， with platform-margin shoals along the Linshui-Fengdu and Dazhu-Zhongxian platform-margin zones spreading in the NW-SE direction. During the deposition of sub-layer 1， platform-margin shoals in both platform-margin zones display pronounced differentiation， separated by banded inter-shoal lagoons. During the deposition of the sub-layer 2， platform-margin shoals display lateral migration and an expanded planar distribution area， manifesting a contiguous development in the eastern part. The superimposition of penecontemporaneous karstification and dolomitization on platform-margin shoals is identified as the main cause of the formation of high-quality reservoirs. The Linshui-Fengdu and Dazhu-Zhongxian platform-margin zones are favorable for reservoir development， while slope-troughs and inter-shoal lagoons emerge as favorable areas for source rock development. The platform-margin shoals along the Dazhu-Zhongxian platform-margin zone exhibit great hydrocarbon exploration potential， serving as a new hydrocarbon play fairway.

10.11743/ogg20250115