Space-Time Evolution and Controlling Factor of Fine-Grained Sediments in the Upper Fourth Member of Shahejie Formation, Dongying Depression
Guoqi Song;Jing Wu;Yong Wang;Xuefeng Hao;Geological Science Research Institute,SINOPEC Shengli Oilfield Company;Petroleum Exploration and Production Research Institute of SINOPEC;SINOPEC Key Laboratory of Shale Gas/Oil Exploration & Production;
Fine-grained rocks(FGR) are the important source rocks and reservoirs of shale hydrocarbon which is the prospect hotspot at present. Widely distributed fine-grained sediments(FGS) of the upper fourth member of Shahejie Formation in Dongying depression are taken as an example to study the space-time evolution and controlling factor of FGS in this paper. Based on the analysis of well cores, thin sections, inorganic and organic geochemistry indicators, FGR are divided into 7 types of lithofacies. Through the study of ‘point-line-plane', this study shows that FGS has the characteristics of rhythum, diversity and succession. The first stage is characterized by clayey FGS(massive claystone). The second stage is characterized by carbonate FGS(low-TOC laminated limestone) and dolomitic FGS(dolomitic-silty shale) formed by transgression. The third stage is characterized by organic-rich carbonate FGS(middle/high-TOC laminated limestone) distributed in cycle. The fourth stage is characterized by FGS mixed carbonate and siliciclastic sediments(calcareous-silty shale). A variety of space-time evolution of FGS are controlled by multiple factors including tectonism, climate and lake conditions.