Fourier-Transform Infrared Proxies for Oil Source and Maturity: Insights from the Early Permian Alkaline Lacustrine System, Junggar Basin (NW China)

Fourier-transform infrared (FTIR) spectroscopy has been widely applied in oil geochemical studies, particularly with respect to the physical properties and maturity of hydrocarbons. However, in general, it has been seldom used to investigate the organic matter (OM) depositional environment and source of oil. In this paper, we present such an FTIR spectroscopy study based on a case investigation in the early Permian alkaline–lacustrine-derived oils from the Mahu sag, Junggar Basin, Northwest China. The results define 13 FTIR structural parameters that are associated with the OM depositional environment, source, and maturity of oil based on a comparison with well-established oil carbon isotopic and biomarker data. These would be general to the alkaline (saline)–lacustrine petroleum systems worldwide. Further combined FTIR spectroscopy and biomarker parameters in the study area reveal that the lower Permian Fengcheng formation-derived oils in the Mahu sag were generated from source rocks deposited in alkalin...