Application of single hydrocarbon inclusions in petroleum geochemistry: A case study of the Tahe oilfield

The hydrocarbon accumulation period and petroleum source characteristics in the Tahe oilfield were discussed using the newly developed methods for hydrocarbon inclusion analyses. The results confirmed that there were many stages of hydrocarbon accumulation in the Tahe oilfield, especially predominated by the Middle Hercynian and the Late Himalayan. The online laser ablation compositional analyses of single hydrocarbon inclusion showed that the early oil (yellow fluorescing inclusion) was characterized by bimodal n-alkane distribution and higher aromatic component content, belonging to medium crude oil with relatively lower maturity. In contrast, the late oil (blue fluorescing inclusion) was featured by unimodal n-alkane distribution and lower aromatic component content, belonging to late light crude oil at the middle-late mature stage. Based on the petroleum source or sedimentary environment of source rocks, hydrocarbon-forming organisms, maturity, migration distance, accumulation process and period, the early oil was suggested mainly from -C₁-O₁ excellent source rocks and the late oil was mainly from O₃ carbonate source rocks.