Research on basic elements of coal measure gas-bearing system in Jiaozuo mining area
Coal measure gas is an important natural gas resource,and clarifying the basic elements of the coal measure gas-bearing is crucial for the exploration and development of coal measure gas.Taking the coal measure gas-bearing system of the Carboniferous-Permi-an transitional phase in the Jiaozuo mining area as an example,the basic elements and characteristics of the coal measure gas-bearing system in the study area were systematically described from four aspects:generation,storage,seal,and overlying strata.The results show that the hydrocarbon source rocks in the Carboniferous-Permian series in the mining area are mainly composed of coal and dark mud-stone.The total organic carbon(TOC)contents of mudstones in the Taiyuan Formation,Shanxi Formation,and Lower Shihezi Formation of Machang 1 Well are 1.68％,0.905％,and 4.35％,respectively.The contents of S1+S2 in the mudstone of the roof and floor of the Ⅱ1 coal seam is 0.452 and 0.576 mg/g,respectively,reaching a good level of hydrocarbon source rock.From the aspects of vitrinite content and type index,it was determined that the source rock was of type Ⅲ organic matter type.The overall degree of thermal evolu-tion of hydrocarbon source rocks was in the mature to over mature stage,and was in the main gas generation stage.The reservoirs are mainly composed of coal,followed by mudstone and some sandstone.Its gas content is divided into 11.54-23.16,1-3,and 0.18-1.47 m3/t.The mineral composition of the reservoir is mainly quartz and clay minerals,mainly developing plant cell pores and pores.The porosity ranges from 0.80％to 11.08％,and the permeability ranges from 0.004 × 10-3 to 0.012 × 10-3 μm2,exhibiting low po-rosity and low permeability physical properties.The saturation pressure at which gas starts to be released from Taiyuan Formation,Shanxi Formation,and Lower Shihezi Formation mudstones ranges from 5.88 to 9.80 MPa,and the breakthrough pressure of saturated kerosene is 13.72-14.11 MPa,with good sealing capacity.Research suggests that the combination relationship of the basic elements of the Car-boniferous-Permian coal measure gas-bearing system in the Jiaozuo mining area is that the source rocks are developed from the Taiyuan Formation to the Lower Shihezi Formation,the dominant reservoir is the Shanxi Formation,the upper Shihezi Formation is the regional cap rock,and the Quaternary and Neogene are the overlying strata in the study area.
coal measure gas-bearing systemhydrocarbon source rockreservoir layercover layeroverlying stratabasic element
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