四川盆地北部及周缘地区震旦系灯影组二段、四段储集层特征及成因差异

Reservoir characteristics and genetic differences between the second and fourth members of Sinian Dengying Formation in northern Sichuan Basin and its surrounding areas

基于野外露头、钻井岩心的宏观与微观研究,结合相关地球化学分析资料,对四川盆地北部及周缘地区震旦系灯影组二、四段储集层特征及成因进行了探讨与对比。研究认为:区内灯影组二段储集层分布于地层中部,主要受丘滩复合体和表生期岩溶作用的共同控制,近顺层分布的拉长状孤立藻格架溶洞和残余"葡萄花边"洞构成其储集空间主体,其中部分空间被多期亮晶白云石半充填,未见有沥青分布,连通性较差,多属于低孔、低渗型储集层;灯影组四段储集层在地层中上部—顶部发育,受丘滩集合体和埋藏溶蚀作用控制明显,近顺层分布的藻格架溶孔、溶洞、晶间孔和晶间溶孔构成其主要储集空间,其中部分空间被较多沥青和少量石英半充填,几乎未见亮晶白云石分布,连通性相对较好,多属于中—低孔、低渗型储集层,局部为中高孔、中渗型。受丘滩复合体发育程度与溶蚀作用差异的共同影响,沿宁强—广元—剑阁—阆中一线分布的台地边缘是最有利于优质储集层发育的区带,深埋地表之下的广元—阆中一带则是今后该领域油气勘探的主要地区。

This study investigated the characteristics and genesis of reservoirs in the 2nd and 4th members of Sinian Dengying Formation in northern Sichuan and its surrounding areas,on the basis of outcrop,drilling cores and thin section observation and geochemical analysis.The reservoirs of 2nd member are distributed in the middle part of the stratum.The reservoir quality is controlled by supergene karst and the distribution of mound-shoal complex.The bedded elongated isolated algal framework solution-cave and the residual“grape-lace"cave,which are partially filled with multi-stage dolosparite,constituted the main reservoir space of the 2nd member.There is no asphalt distribution in the pores.The pore connectivity is poor,and the porosity and permeability of the reservoir is relatively low.The reservoirs of 4th member were distributed in the upper and top part of the stratum.The reservoir quality is controlled by burial dissolution and the distribution of mound-shoal complex.The bedded algal framework solution-pores or caves,intercrystalline pores and intercrystalline dissolved pores constituted the main reservoir space of the 4th member.It’s partially filled with asphalt and quartz,without any dolosparite fillings in the pores and caves.The pore connectivity is good.Most of the 4th member reservoirs had medium-low porosity and low permeability,and,locally,medium-high porosity and medium permeability.Affected by the development of mound-shoal complex and heterogeneous dissolution,the platform margin along Ningqiang,Guangyuan,Jiange and Langzhong is the most favorable region for reservoir development.Deep buried Dengying Formation in the guangyuan and langzhong areas should be the most important hydrocarbon target for the future exploration.