Molecular geochemical characteristics of gas source rocks from the Upper Triassic Xujiahe Formation indicate transgression events in the Sichuan Basin

作者：Zhang Min^*; Huang GuangHui; Li HongBo; Hu GuoYi; Zhang ShuiChang

来源：Science China Earth Sciences, 2012, 55(8): 1260-1268.

DOI：10.1007/s11430-012-4408-1

• gas source rock
• biomarker
• transgression event
• Upper Triassic
• Sichuan Basin

The geochemical characteristics of saturated and aromatic hydrocarbons from different formations and lithologies provide obvious evidence for transgressions that occurred during Upper Triassic Xujiahe stage in Sichuan Basin with a great impact on the source input and depositional environment. A clear dual peak distribution for normal alkanes and obvious abundant compounds sourced from bacteria and algae in whole oil gas chromatogram indicates the abundance of lower organisms input. The ratio of Pr/Ph is low, ranging from 0.33 to 0.86 with an average of 0.60, quite different from Pr/Ph > 2.0 for coal measures in swamp environment, representing source rocks from saline lake or marine facies. In the gas source rocks extracts, abundant beta-carotane, gamma-carotane, and their degradated series were detected in the whole oil chromatogram, indicating a reducing environment. The concentrations of methyl steranes and dinosteranes are high. The content of polycyclic aromatic sulfur heterocycles (PASH) is relatively higher in aromatic fraction and the assemblage of fluorene, dibenzofuran, and dibenzothiophene is different from the typical saline lake and the regular swamp facies source rocks, manifesting the transgression effects on gas source rocks.

• 出版日期2012-8
• 单位中国石油天然气股份有限公司勘探开发研究院; 长江大学