四川盆地南部龙王庙组膏盐岩沉积环境及其对储层成岩作用的影响

摘要

Based on field profiling,drilling cores,rock sections,carbon and oxygen isotopes,and physical properties of rocks,analyzed the distribution characteristics,sedimentary environment and reservoir characteristics of gypsumsalt rocks of Lower Cambrian Longwangmiao Formation in southern Sichuan Basin,the gypsum-salt rock has the influence on reservoir diagenesis and the reservoir distribution range are predicted in region of interest.The results show that:①The thickness of Longwangmiao formation gypsum rock varies widely in sedimentary period and thickness isoline is roughly NE-SW trending,the sedimentary center located in Changshou—Hejiang;②The gypsum rock in Longwangrniao formation of study area mainly forms in the supratidal Sabkha,the intertidal and the subtidal limitation lagoon depositional environment;③The reservoir physical property is better in southwest of Sichuan,the dolomitization is dominated by evaporation concentration and reflux infiltration and the reservoir physical property is poor in southeast of Sichuan.The dolomitization in these area is mainly controlled by reflux osmosis;④The influence of gypsum salt rock on reservoir diagenesis is mainly controlled by sedimentary facies and later stage tectonism.The influence of gypsum salt rock on reservoir diagenesis is mainly constructive in Southwest of Sichuan,the reservoirs distribute between Nanchong—Ziyang and Hechuan—Weiyuan.But the intluence of gypsum salt rock on reservoir diagenesis is mainly destructive in Southeast of Sichuan and the reservoirs distribute in Nanchuan—Xishui.%应用野外剖面、钻井岩心、岩石薄片、碳氧同位素和岩石物性分析资料,分析了四川盆地南部龙王庙组膏盐岩的分布特征、沉积环境、储层特征,探讨了膏盐岩对储层成岩作用的影响,辅助判断研究区有利储层分布范围.研究结果表明:①研究区下寒武统龙王庙组膏盐岩厚度等值线大体呈北东南西向展布,沉积中心位于长寿—合江一带;②龙王庙组沉积时期膏盐岩主要形成于潮上萨布哈、潮间膏盐湖与潮下局限潟湖环境;③川西南储集物性较好,储层白云石化以蒸发浓缩和回流渗透作用为主;川东南储集物性较差,储层白云石化以回流渗透作用为主,两地区储层的形成都与膏盐岩沉积环境有密不可分的关系;④膏盐岩对储层成岩作用的影响,主要受沉积环境和后期构造作用控制;川西南地区膏盐岩对储层起建设性作用,储层分布于南充—资阳和合川—威远之间;而在川东南地区膏盐岩对储层起破坏性作用,储层主要分布于南川至习水一线.