Hydrocarbon generation potential and geochemical characteristics comparison of source rocks in the Southwestern Qaidam basin, China

A primary source rock has developed in the Upper part of the Lower Ganchaigou Formation (E32) in the southwestern Qaidam Basin, China. This basin features typical brackish-saline lacustrine deposits, necessitating careful selection of appropriate standards for evaluating hydrocarbon generation potential. The presence of multiple sets of source rocks and complex migration pathways has led to the accumulation of mixed-source oils, complicating the relationship between crude oil and source rocks and the establishment of hydrocarbon migration system. To address these challenge, 113 source rock samples were analyzed using Rock-Eval 6, gas chromatography-mass spectrometry and microphotometer. R-type clustering and principal component analysis were employed to select two out of five biomarker parameters that reflect water salinity and parent material sources for Q-type clustering. The results indicate that the E32 source rock exhibits fair hydrocarbon potential and is predominantly composed Type I and Type II1 kerogens. It remains in a low-maturity to mature stage, with deposition occurring in environments characterized by either strong reduction and high salinity or relatively weak reduction and low salinity. The oil is derived from nearby source rocks in the Hongshi, Yingxiongling, and Chekrike-Zahazquan depressions. This study provides new insights into source rock evaluation and oil-source relationship analysis.