Simulation of Gas Generation from the Paleogene Enping Formation in the Baiyun Sag in the Deepwater Area of the Pearl River Mouth Basin, the South China Sea

Abstract

The deepwater area of the Baiyun Sag is the primary region of deepwater oil and gas exploration in China. Since the breakthrough made in natural gas exploration in the structure of the LW3-1 gas field, explorers have given significant attention to the conditions and process of gas generation and to the accumulation and preservation of natural gas. The Paleogene Enping Formation provides one of the two sets of major source rocks in the Baiyun Sag. We selected three samples of source rocks from the Enping Formation, performed a thermocompression simulation experiment, calculated the hydrocarbon generation kinetic parameters, and simulated single-well gas generation to explore the process of gas generation in the gasgenerating center of the Enping Formation in the Baiyun Sag. The major conclusions included the following: (1) The lacustrine dark mudstone and the carbonaceous mudstone from the Enping Formation in well HZ08-1-1 have hydrocarbon yields of 383.7 versus 307.3 kg/t of total organic carbon (TOC) and gas yields of 370.1 versus 302.9 kg/t of TOC. (2) The thermal evolution of the Enping Formation in the Baiyun Sag can be divided into three evolutionary stages. (3) Finally, the source rocks of the Enping Formation have a gas generation peak from approximately 17.5 to 8 Ma.

Characteristics and Hydrocarbon Generation of the Marine Source Rock of the Upper Oligocene Zhuhai Formation in the Baiyun Sag, Pearl River Mouth Basin, South China Sea

“…The hydrocarbon generation kinetic parameters of kerogen in the Upper Oligocene Zhuhai Formation source rocks were adjusted using the Basin Mod 1D and 2D, and then, they were used for the hydrocarbon generation simulation. 17 According to the experiments and simulation results, the Zhuhai source rock is in the main hydrocarbon generation stage (Table 2 and Figure 7), the activation energy values range from 46 to 63 kcal/mol (Table 3 and Figure 8), the frequency factor is 1.91 × 10 13 s −1 , and the original hydrocarbon generation potential values range from 4 to 12%. The hydrocarbon generation potential values generally exhibit a normal distribution, with high levels of 7−12% corresponding to activation energy values of 50−60 kcal/mol.…”

“…The strata of the Baiyun Sag are chronologically composed of the Paleocene to Eocene Shenhu, Eocene Wenchang, the late Eocene to Lower Oligocene Enping, Upper Oligocene Zhuhai, Lower Miocene Zhujiang, Middle Miocene Hanjing, Upper Miocene Yuehai, and Pliocene Wanshan Formations and the Quaternary stratum. 17 The Shenhu and Wenchang Formations represent the deposition of the rift stage; the Enping Formation represents the deposition of the rift depression stage; the Zhuhai Formation represents the deposition of the transition stage; and the Zhujiang, Hanjiang, Yuehai, and Wanshan Formations, along with the Quaternary stratum, represent the deposition of the depression stage 18 (Figure 2). According to Liu et al 13 and He 18 , the Upper Oligocene Zhuhai Formation is composed of littoralneritic sandstone and mudstone deposits.…”

“…The Baiyun Sag experienced three evolutionary stages: the rift stage (Paleocene to Early Oligocene), the transition stage (the Late Oligocene), and the depression stage (Early Miocene to the present). 4,17,38,39 The corresponding heat flow evolved from the rifting heat flow model to the passive continental margin basement heat flow model, and the thermal history of the Baiyun Sag can be simulated on the basis of its burial history and the measured R o values of wells A and C (Figure 9). 17,40−48 The thermal evolution simulation results for well A indicate that the Upper Oligocene Zhuhai Formation has a relatively low degree of thermal evolution, with R o values ranging from 0.64 to 0.78%, which is consistent with the test results (well A in Figure 9).…”

“…Stratigraphic column with formation, main seismic reflectors, tectonic events, and unconformities of the Baiyun Sag (modified with permission from refs , , and ).…”

Reconstruction of the Cenozoic History of Hydrocarbon Fluids from Rifting Stage to Passive Continental Margin Stage in the Huizhou Sag, the Pearl River Mouth Basin

“…Jiang et al [61] analyzed the chemical kinetic equations of the Enping dark mudstone and carbonaceous mudstone, which showed that dark mudstone has an activation energy of 49.5∼ 64 kcal/mole with a normal distribution of the hydrocarbon generation potential, and carbonaceous mudstone has an activation energy of 46∼66 kcal/mole, showing a skewed distribution of the hydrocarbon generation potential. These results of our previous papers were adopted in this paper.…”