Geological characteristics and resource potential of the Upper Sinian Doushantuo Formation shale gas in the north of middle Yangtze region

Abstract: Based on the test data including the observation and measurement of mud shale in the field geological sections and a well, the result of organic geochemistry experiment, physical analysis and the component analysis of the rock mineral samples, the authors systematically investigated the characteristics of sedimentary environments, the scale of development, geochemistry and reservoir of Upper Sinian Doushantuo Formation black shale in the north of middle Yangtze region. The results show that the thickness of black mud shale is approximately 53.3-114.7 m with an average of 87.3 m, the mud shale is mainly developed in the intra-platform basin, the total organic content is generally over 1.0%, the main organic type is I-Ⅱ1, the average value of organic material maturity is 1.85%, Tmax is mainly in the range of 353-609 ℃, and the black mud shale is mainly composed of detrital minerals and clay minerals. In addition, the average content of detrital minerals is 56.3%, the ingredients are mainly quartz and feldspar, the average content of clay minerals is 26.1%, the ingredients are mainly illite and smectite mixed layer minerals, the average of porosity is 2.32%, and the average permeability is 0.031857×10-3 μm2. Compared with the indicators of the main mud shale gas production areas in the USA and China, Upper Sinian Doushantuo Formation mud black shale in the north of Middle Yangtze region has a larger thickness, relatively?low organic matter, higher thermal evolution degree, higher brittleness mineral content, lower clay mineral content, lower shale porosity and permeability, and better preservation?condition. The study area which has the basic geological conditions for producing shale gas is one of the main marine shale gas prospecting?areas in China.