Hydrocarbon Generation in the Lacustrine Mudstones of the Wenchang Formation in the Baiyun Sag of the Pearl River Mouth Basin, Northern South China Sea

Abstract

The lacustrine mudstones of the Eocene Wenchang Formation are the primary source rocks of natural gas in the Baiyun Sag of the Pearl River Mouth Basin, China. The hydrocarbon generation kinetic parameters and the characteristics of lacustrine mudstones sampled from the Eocene Wenchang Formation at well LF13-2-1 were investigated on the basis of a thermocompression simulation experiment in a closed system. In addition, combined with the burial history and paleothermal history, the gas generation process of the Eocene Wenchang Formation source rocks in the Baiyun Sag was investigated through the hydrocarbon generation equations established from parameters of hydrocarbon generation kinetics. The gas generation process of the Eocene Wenchang Formation lacustrine mudstones has three thermal evolutionary stages: the middle mature stage (39–30 Ma), the late mature stage (30–23.5 Ma), and the main gas generation stage (23.5–0.0 Ma). The main hydrocarbon generation stage in the central area of the Baiyun Sag occurred from 24 Ma to 22 Ma, while the main hydrocarbon generation stage in the eastern and northern areas occurred at ∼15 Ma.