四川盆地东南部及周缘震旦系-寒武系微生物岩成岩作用与孔隙演化

Selecting Sinian Dengying Formation, Cambrian Longwangmian and Loushanguan Formations in southeastern Sichuan Basin and its peripheral regions as target, the diagenetic processes and porosity evolution of microbialites in those Formations are researched. Based on petrographic and geochemical features of the different composition and fabric in microbialites, the sedimentary environment and pattern are analyzed. According to petrographic and geochemical features of diagenetic composition and fabric, paragenetic diagenesis sequence is illustrated. The primary and secondary porosity characteristics of different microbial rocks are summarized. Based on petrographic and geochemical features of fillings, filling types and porosity types, different stages of dissolutions are proposed. The environments of different dissolutions are discussed and the mechanisms and patterns of dissolutions are established. According to petrographic and geochemical features of various dolomites, the dolomitization fluids are analyzed and the dolomitization patterns are discussed. The effects of dissolution, dolomitization and hydrothermal activity on porosity development and evolution are discussed. On the basis of the effect of diagenesis to porosity development and evolution, constructive and destructive diagenesis types are divided. Porosity evolution model and reservoir quality of different microbialites are discussed and established. This is especially useful for further understanding microbialite reservoir formation and development, and thus has significant implications for deep hydrocarbon exploration of china.

选择川东南及周缘地区作为解剖区，以震旦系灯影组、寒武系龙王庙组和娄山关组为目的层系，进行微生物岩成岩作用和孔隙演化研究。利用微生物岩不同组构的岩石学和地球化学特征，分析其沉积环境并建立沉积模式，进行微生物岩成岩组分和成岩作用分析，建立成岩序列；总结不同微生物岩的原始孔隙和次生孔隙特征；识别微生物岩溶蚀作用，提出不同期次溶蚀作用的充填物类型、充填物地球化学特征和孔隙类型，探讨各期次溶蚀作用发生的介质环境，建立微生物岩不同期次溶蚀作用的机制和模式；分析不同白云石化作用的介质环境，阐释不同白云岩的白云石化模式；探讨不同期次溶蚀作用、白云石化作用和热液作用对孔隙形成和演化的影响，划分孔隙建设性和破坏性成岩作用，结合不同微生物岩的物性特征，建立不同微生物岩的孔隙形成与演化模式。该研究不仅有利于进一步了解深层微生物岩储层的形成与演化，对我国深层油气勘探也具有重要意义。

深层微生物岩储层富含油气藏，勘探开发前景广阔，是我国深层油气勘探的新领域和重要目标。然而深层微生物岩储层成岩作用和孔隙演化的系统研究还比较缺乏，导致深层微生物岩储层形成机制还存较大争议，制约了该类储层的规模勘探和高效开发。为此，本项目以川东南及周缘地区震旦-寒武系微生物岩为研究对象，在野外剖面和钻井岩心观察的基础之上，利用岩相学、岩石学和地球化学的研究方法，开展了单井层序地层划分和沉积微相研究，明确了不同微生物岩沉积环境和模式；分析了不同微生物岩成岩组分和成岩作用，分别建立了不同地区、不同类型微生物岩的成岩序列；利用溶蚀（岩溶）作用发生的组构类型、充填物类型、充填物地球化学特征和孔隙（孔洞）类型，明确了不同期次溶蚀（岩溶）作用识别标志，建立了微生物岩不同期次溶蚀作用的机制和模式；利用不同白云石组构类型、赋存状态和地球化学特征，厘清了多期白云石化流体来源，阐释了多期白云石化的机制和模式；结合物性分析，探讨了不同期次白云石化作用、溶蚀作用和热液作用对孔隙形成和演化的影响，建立不同微生物岩的孔隙形成与演化模式。综合分析认为，准同生期溶蚀作用和风化壳岩溶作用是微生物岩孔隙（孔洞）发育的关键，早期白云石化是微生物岩孔隙（孔洞）得以保持的核心，埋藏-热液作用是微生物岩孔隙（孔洞）发育的重要补充。优质微生物岩储层多受沉积相带、风化壳岩溶作用和埋藏-热液岩溶作用联合控制。研究成果深化和丰富了深层微生物岩储层形成机制与分布规律，对四川盆地震旦-寒武系微生物岩储层油气勘探部署有一定的指导意义。