Relationship between sedimentary facies and source rocks of Permian strata in Huainan coalfield

The relationship between sedimentary facies evolution characteristics and hydrocarbon source rocks was analyzed on the basis of observational related test of the geochemical parameters, lithology, minerals and fossils. Seawater retreated in oscillation during Early and Middle Permian Periods in Huainan area, forming mainly underwater deposits. Permian strata in Huainan area can be roughly divided into two subfacies:underwater delta deposits in Shanxi Formation and distributary channel deposits in Lower Shihezi Formation. It can be further broken down into:peat swamp, distributary channel, crevasse splay, flood plain, tidal flat and lagoon microfacies. Among them, shale and coal seam were most generated in former delta and floodplain microfacies. Lithological and microstructure components were significantly controlled by micro environmental change, (exinite plus sapropelinite)/∑macerals is generally greater than 70%, conducive to generation hydrocarbon; organic carbon content jointly controlled by sedimentary subfacies and sedimentary role of microenvironment, organic carbon content of about 2.78 percent on average in the shale of Shanxi Formation was significantly more than that in the shale of Lower Shihezi Formation(about 1.11%), but under the same conditions the organic matter of Lower Shihezi shale may be more conducive to generation hydrocarbon. Considering the factors such as the cumulative thickness of shale, organic carbon content and composition of organic matter, in this region the shale of Shanxi and Lower Shihezi Formation can be used as favorable shale gas exploration layers, in particular the "Panji Town-Panji District-Nihe Town-Pingwei Town" is the most favorable area.