Organic geochemical study of FTIR analysis on source rock extracts: a case study of Lower Permian Fengcheng Formation in Junggar Basin, NW China

Abstract

To discover the values of Fourier Transform Infrared Spectroscopy (FTIR) in the research of organic geochemistry, hydrocarbon generation features of source rocks of Lower Permian Fengcheng, Junggar Basin were studied by the means of FTIR analysis on the extracts. Seven FTIR functional groups appeared to have indicative significance, based on which three new index were proposed, including A index (A2 920/A3 600), B index (A2 920/A1 460), and C index (A1 140/A1 600). Specifically, A index unraveled a higher hydrocarbon generation potential of the source rocks located in saline areas, B index indicated that the possible hydrothermal fluid injection have caused the abnormal thermal evolution of organic matter in saline source rocks, and C index showed that an increasing salinity from marginal zone to saline zones has affected to the organic molecular polymerization in the Fengcheng Formation source rocks. Based on that, the saline zone located at the center of Fengcheng Formation deposition has great potential for oil-gas exploration, particularly for light oils in the deep reservoirs. These understandings provided new references for the regional oil-gas exploration and pointed out that FTIR can supplement traditional organic geochemistry, displaying a broad application potential.

Keywords

• fourier transform infrared spectroscopy (ftir)
• sedimentary organic matter
• hydrocarbon generation potential
• alkaline lacustrine
• fengcheng formation
• junggar basin