Kinetic analysis of hydrocarbon generation based on saline lacustrine source rock and kerogen samples in the western Qaidam Basin, China

Tertiary carbonate rocks from the Qaidam Basin in China are typical plateau saline lacustrine source rocks. Despite the fact that this set of source rocks has a relatively low abundance of organic matter (major frequency of total organic carbon, 0.4-0.6%), the organic matter has a high hydrocarbon conversion rate and commonly forms low-maturity oil. In this study, a comparative analysis was conducted on Tertiary source rock and kerogen samples from the Qaidam Basin using a kinetic experiment of hydrocarbon generation. The objectives of the study were to investigate the mechanism of hydrocarbon generation from source rock to low-maturity oil and the catalysis of kerogen pyrolysis by minerals. The results showed that both the source rock and kerogen samples reached a maximum liquid hydrocarbon yield during the low-maturity stage. Eighty percent of the hydrocarbons were expulsed before the Easy Ro reached 0.8%. Special algal parent materials in the saline lacustrine basin could be the primary cause that leads to generating low-maturity oil. Compared to the kerogen samples, the source rock was more prone to hydrocarbon generation via pyrolysis. The latter had a higher liquid hydrocarbon yield per unit organic matter and a lower activation energy; thus, it entered the hydrocarbon generation threshold earlier. The key factor for the aforementioned differences might be catalysis by minerals (particularly carbonate minerals) and the presence of soluble organic matter in the source rocks.