川中侏罗系致密页岩油储层方解石沉淀模式及油气关系  

Precipitation model of calcite and relation with hydrocarbon of the Jurassic tight shale oil reservoir in central Sichuan Basin

作　　者：冯明友[1,2] 岳怀海 刘小洪[1,2] 张芮 王兴志[1,2] 祝海华[1] 王委委 李沛珈 FENG Mingyou;YUE Huaihai;LIU Xiaohong;ZHANG Rui;WANG Xingzhi;ZHU Haihua;WANG Weiwei;LI Peijia(School of Geoscience and Technology,Southwest Petroleum University,Chengdu 610500,China;Natural Gas Geology Key Laboratory of Sichuan Province,Southwest Petroleum University,Chengdu 610500,China;Exploration and Development Institute,PetroChina Southwest Oil and Gas Field Company,Chengdu 610400,China)

机构地区：[1]西南石油大学地球科学与技术学院,四川成都610500 [2]西南石油大学天然气地质四川省重点实验室,四川成都610500 [3]中石油西南油气田分公司勘探开发研究院,四川成都610400

出　　处：《中南大学学报（自然科学版）》2022年第9期3449-3461,共13页Journal of Central South University:Science and Technology

基　　金：国家科技重大专项(2017ZX05001-001);中国石油-西南石油大学创新联合体科技合作项目(2020CX050103)。

摘　　要：四川盆地侏罗系大安寨段致密页岩油储层中页岩与介壳灰岩不等厚互层为有利岩性组合层段,该段页岩中发育不同结构特征的水平状方解石脉,介壳灰岩中亦发育多期方解石胶结物,然而成形机制不明确。本文结合系统显微薄片观察、电子探针成分分析等,综合方解石产状、主量元素及共生矿物特征,探讨湖相致密页岩油储层中方解石沉淀模式及与油气关系。研究结果表明:川中侏罗系大安寨段富有机质页岩中广泛发育沿水平缝分布的叠锥状、纤维状、壳−核结构方解石脉及薄层介壳灰岩夹层,不同结构特征的水平方解石脉均为流体超压作用的产物;而介壳灰岩夹层显现的不同成岩演化序列亦与由超压引起的一系列化学反应有关;有机质生烃及其副产品有机酸的存在共同影响介壳演化及方解石的沉淀过程,其中,最大湖泛面附近具最大TOC质量分数(w(TOC))页岩中的介壳灰岩夹层经历了强烈的有机酸溶解−方解石再沉淀作用,最终导致溶蚀孔缝中方解石与大量矿物沥青及固体沥青共存。In the tight shale oil reservoir of Da'anzhai Formation(Lower Jurassic)in Sichuan Basin,the layered thin shale and shell limestone interbeds are beneficial lithology combination section,and horizontal calcite veins are developed with different structural characteristics.Multistage calcite cements are developed in the shell limestone.Based on detailed microscopic section observation,electron probe composition integrated with the calcite occurrence,trace elements and paragenous minerals,the precipitation model of calcite and its relationship with hydrocarbon in lacustrine tight shale-oil reservoirs were discussed.The results show that the organic-rich shale of Da'anzhai Member in central Sichuan Basin wildly develops cone-in-cone,fibrous,shell-core calcite veins along the horizontal fractures and thin shell limestone interlayer.Horizontal calcite veins are the products of fluid overpressure.However,the different diagenetic evolution sequences in the shell limestone interlayer are also related to different chemical reactions caused by overpressure.The existence of organic matter hydrocarbon generation and its byproduct organic acid common affect the evolution of the shale and the sedimentation process of calcite.In addition,the shale limestone interlayer with the maximum total organic carbon(TOC)value near the maximum flooding surface experiences strong organic acid dissolution and calcite re-precipitation action,which eventually induces the coexistence of calcite and massive mineral asphalt and solid asphalt in the dissolution pores.

关 键 词：四川盆地 侏罗系 致密页岩油 流体超压 方解石沉淀 

分 类 号：P588.245[天文地球—岩石学] P595[天文地球—地质学]