Abstract:

The marine sedimentary sequence in southeastern China was widely altered by the

complicated multi-stage magmatic activities. In spite of high organic abundance in some strata, the

characteristics and controlling factors of thermal evolution and hydrocarbon generation are still

not clear, which restricts further understanding in basic petroleum geologic problems. Taking

Permian coal measures in Yongmei depression as an example, based on the determination of vitrinite

reflectance and volatile index and combined with the study of geological background and thermal

modelling, the thermal maturation of hydrocarbon source rocks and their distribution was analyzed,

and the evolution history of hydrocarbon generation was constructed. The results show that,

generally speaking, the coal hydrocarbon source rocks have attained the phase of post-mature-dry

gas. Horizontally, thermal maturation is increasing from west to east; and vertically, thermal

evolution is not related to depth of burial. According to the history of thermal evolution and

hydrocarbon generation, the Yanshanian stage is an important period for drastic change in thermal

history of the Yongmei depression. Thermal evolution of the Permian source rocks was affected and

metamorphosed by several thermal sources, among which the magmatic activities resulted in

anomalously high metamorphism of marine source rocks in this region.

Key words: Southeast China, Yongmei depression, Permian, coal measures, hydrocarbon source rocks; thermal evolution, magmatic activities