Symbiotic accumulation characteristics of coal measure gas in Linxing Block,eastern Ordos Basin

With the constant development of production technology,the co-exploration of coal measure gas becomes possible. Since the co-exploration of coal measure gas is based on the co-existence of coal measure gas,the study on the co-existence of coal measure gas has important guiding significance to the co-exploration. Based on the study of source rock,reservoir rock and cap rock of coal measure gas in Linxing block,eastern Ordos Basin,as well as the ob- servation of rock core and field geology trip,this paper summarizes the co-existence patterns of coal measure gas,and discusses the origin mechanism of coal measure gas in terms of sedimentation and diagenesis. Results show that No. 8+9 coal seams in Benxi formation and Nos. 4+5 coal seams in Shanxi formation are the main source rocks. Dark muddy shales have a certain capacity of hydrocarbon generation. The type of sandstone is mainly lithic sandstone,whose aver- age porosity is 6． 2% and average permeability is 0． 14 ×10-15 m2 ,meaning it belongs to tight sandstone. Tight sand- stone,shale and coal seam are cap rock to each other,which leads to 14 combination modes between any two of tight sandstone gas,gas and coalbed methane. And the composition pattern of coal measure gas can be divided into four categories. Sedimentation determines the formation of CMG and the diagenesis affects its co-existence.