Hydrocarbon potential and sedimentary environment of organic matter in source rocks of Linhe and Guyang Formations in Linhe depression, Hetao Basin

Since 2017, the Hetao Basin has achieved large-scale oil and gas production. The Paleogene Linhe and Lower Cretaceous Guyang Formations are the main source rocks in Linhe depression. The hydrocarbon generation potential and the characteristics of the organic sedimentary environment have not been systematically studied for these two sets of source rocks, which restricts the calculation of resources. Rock–Eval pyrolysis, total organic carbon (TOC), chloroform bitumen “A,” and vitrinite reflectance (Ro) analyses were designed to explore their hydrocarbon generation potential. Using saturated hydrocarbon gas chromatography-mass spectrometry (GC–MS) and trace element analysis, the feature of the depositional environments of the Linhe and Guyang Formations was analyzed. The results show that both the Linhe and the Guyang Formations have good hydrocarbon generation potential, the southern part is low maturity, and the northern part is in the mature stage. The Linhe Formation was depositional in a brackish water-salt water reducing environment. The depositional environment of the southern part of the Guyang Formation was the same as that of the Linhe Formation, but water stratification occurs in the northern part of the basin, and the depositional environment has changed. This sedimentary environment in the Linhe depression was favorable for the enrichment and preservation of organic matter. Salinity affects the parameters, CPI can be used to represent the maturity of Linhe Formation, while S /( S + R )-C 29 , ββ/(αα + ββ)-C 29 , and Ts / Tm can be used for Guyang Formation of organic matter maturity study. By comparing the geochemical characteristics of the two sets of source rocks, the hydrocarbon generation potential can be clarified, which can provide theoretical guidance for the future exploration of Hetao Basin. In addition, the relationship between maturity parameters and environmental parameters is discussed, indicating that the application of biomarkers in saline lake environment should be cautious.