四川盆地东部中上寒武统洗象池群油气成藏条件与主控因素

Hydrocarbon accumulation conditions and main controlling factors of the Middle-Upper Cambrian Xixiangchi Group in the eastern Sichuan Basin

孙自明 孙炜 林娟华 马强

SUN Ziming SUN Wei LIN Juanhua MA Qiang

中国石化 石油勘探开发研究院, 北京 102206

SINOPEC Petroleum Exploration and Production Research Institute, Beijing 102206, China

以露头和钻井资料为基础，在对四川盆地东部中上寒武统洗象池群油气成藏条件分析的基础上，结合钻井勘探成果，探讨油气成藏主控因素，明确了洗象池群的有利勘探方向。洗象池群储层以泥晶和粉晶白云岩为主，储集空间主要为白云石晶间孔、晶间溶孔和溶洞等，储层品质一般较差；纵向上，洗象池群具有下寒武统筇竹寺组和上奥陶统五峰组—下志留统龙马溪组2套烃源岩；志留系泥页岩和下奥陶统泥质岩类可分别作为洗象池群的区域盖层和局部盖层；优质储层是洗象池群油气成藏的必要前提，源—储配置样式及其有效性是油气成藏的关键；尽管研究区洗象池群具有上、下2套烃源岩供烃的可能，但受中寒武统膏盐岩层的阻隔，下伏下寒武统筇竹寺组烃源岩生成的油气难以向上运移到洗象池群聚集成藏，而盐上层系发育的一系列断背斜空间上易于构造出五峰组—龙马溪组烃源岩与洗象池群储层有效的源—储配置形式，有利于洗象池群形成“新生古储”油气藏。

The petroleum geological elements and main controlling factors of the Middle-Upper Cambrian Xixiangchi Group in the eastern Sichuan Basin were systematically analyzed on the basis of geological outcrops and drilling data. Results showed that the reservoir lithology of the Xixiangchi Group was mainly micritic and silt-crystal dolomites, and the reservoir space was dominated by dolomite inter-crystalline pores, inter-crystalline dissolved pores and karst caves, etc., at the meantime, the reservoir quality is generally poor. The Xixiangchi Group was vertically composed by two sets of source rocks strata: the underlying Lower Cambrian Qiongzhusi Formation and the overlying Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation. The Silurian shale and the Lower Ordovician argillaceous rocks acted as regional and local cap rocks of the Xixiangchi Group. High-quality reservoirs are the necessary prerequisite for hydrocarbon accumulation in the Xixiangchi Group, and the source-reservoir spatial configuration and its effectiveness are the key factors to hydrocarbon accumulation. Though the Xixiangchi Group could have been charged by natural gas generated from the underlying and the overlying source rocks, it is difficult for the natural gas generated from the underlying source rocks to migrate up to the Xixiangchi Group due to the barrier of the Cambrian gypsum layers. However, the faulted anticlines developed over the Cambrian gypsum layer were favorable for hydrocarbon accumulation because they could change and construct a series of effective source-reservoir spatial configuration between the Wufeng-Longmaxi source rocks and the Xixiangchi reservoirs, and finally formed reservoirs with "young source in old reservoir" in the Xixiangchi Group.

中国石化科技部项目 P19022-3;中国石化科技部项目 P21042-2

https://doi.org/10.11781/sysydz202106933