Evaluation index system for the Permo-Carboniferous mud shale reservoirs of coal measures in Shanxi Province

Aiming to solve the issues of over estimation in geological resources of mud shale gas,the conceptions of in- dependent reservoir and combined reservoir were put forward according to the analysis of the economic limit of gas pro- duction and the average daily gas production attenuation rate of shale gas in the Permo-Carboniferous mud shale reser- voirs of coal-bearing strata in Shanxi Province. The Kerogen type and the total organic carbon content(TOC) of coal- bearing mud shale reservoirs were investigated through 492 mud shale samples. And according to the TOC-normalized methane adsorption capacity and measured gas content,the relation of organic matter maturity and gas content of mud shales were evaluated. The thickness of coal-bearing mud shale was evaluated based on the principle of profile re- sources equivalent compared with marine shale. A classification of buried depth of coal-bearing mud shale was put for- ward according to the positive correlations between buried depth with RO and gas saturation. It was divided into three types such as 1 500 m. Total 128 measured mud shale samples were investigated in their mineral content. And based on the investigation,the brittle mineral content of coal bearing mud shale were divid- ed into three levels of 40% . Finally,six parameters such as the organic matter maturity(Ro ),total carbon content( TOC),buried depth,mud shales thickness,gas content and brittle mineral content were used to classify the marine-terrigenous facies coal-bearing mud shale reservoirs into the favorable,relatively favorable and unfavorable assemblage reservoir.