The atomic H/C ratio of kerogen and its relation to organic geochemical parameters: implications for evaluating hydrocarbon generation of source rock

Abstract

In this study, kerogen samples, including 19 from northwestern Taiwan, 15 from China, and 16 from Australia were analyzed, and integrated with 49 published data, to explore the significance of atomic H/C ratio as a parameter of source rock evaluation. Organic matters in the samples studied are of type II/III kerogen based on the relationship between HI and Tmax. The H/C ratio, as well as the HI, S1, and S2, generally decreases with the maturity increasing. The H/C ratio decreases slightly from 1.1 to 0.7 with the maturity increasing from Ro 0.55 to 0.85 %. Samples with H/C ratio in this range show significant change in certain other geochemical parameters (e.g., HI, S1, S2, S1 + S2, S1/(S1 + S2), S1/TOC, (S1 + S2)/TOC, Tmax). The atomic H/C value is in the range of 0.7–1.1, the value of the corresponding HI shows a stable increasing trend. This shows that organic matters in an oil window of Ro% = 0.55 and atomic H/C = 1.1 have reached a certain maturity and hydrocarbon potential. The QI, HI and H/C ratio shows a certain correlation, all increasing accordingly. It is inferred that hydrocarbon potential started from Ro 0.55 % and atomic H/C ratio 1.1 in this study.