Geochemical features of natural gas source rock in the Upper Paleozoic in the east part of North Shaanxi slope

The east part of North Shaanxi slope is abundant of natural gas,but the research of source rock geochemical features in Upper Paleozoic is very weak. Through the comprehensive analysis of the source rock characters and gas geochemical features of the upper palaeozoic,the hydrocarbon source rock is evaluated. The research results show,1 Gas in the Upper Paleozoic is characterized by a high conten of methane but a low content of non-hydrocarbon gas. The content of heavy hydrocarbons is low and dry coefficient is relatively high,indicating that the gas reservoir is relatively dry as a whole. 2 Coal is the best hydrocarbon source rock,mudstone is the second supplier of natural gas,the mudstone of Shanxi formation is medium to good source rock,the mudstone of Taiyuan formation is good to very good source rock,and Benxi formation is good to excellent source rock. 3 The autogenic coal source rock of Upper Paleozoic is multi-layered parent material inputs,the type of organic matter is humic,Ro generally is more than 2%,indicating that the gas is dry gas at over maturity stage.