The paper adopts some methods such as gas composition , carbon isotope , systematical analyzing and testing of reservoir bitumen biomarker from high evolutional natural gas and quantitative calculation of mixed gas , illustrates that natural gas from the section of jialingjiang formation is mainly attributed to sapropel type organic matter gas of permian , comes from carbonatite hydrocarbon rocks permian which most of them are overmature , its main gas source has nothing to do with carbonatite hydrocarbon rocks of jialingjiang formation themselves , presents in geochemistry characteristics of oil type cracked gas 摘要通过对川中川南过渡带西部的磨溪潼南地区嘉二段天然气组成、碳同位素组成、高演化天然气储层沥青生物标志化合物的系统分析测试和混合成因气的定量估算，阐明了该区嘉二段天然气主要属于二叠系腐泥型有机质成因气，来源于二叠系过成熟为主的碳酸盐岩烃源，主力气源与嘉陵江组自身的碳酸盐岩烃源无关，并具有油型裂解气的地球化学特征。
