Pressure evolution and hydrocarbon migration in the Baiyun sag, Pearl River Mouth basin, China |
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Authors: | Shi Wanzhong Chen Honghan Chen Changmin Pang Xiong and Zhu Ming |
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Institution: | (1) Faculty of Earth Resources, China University of Geosciences, Wuhan, 430074, China;(2) Shenzhen Branch Company, China National Offshore Oil Company Ltd, Guangzhou, 510240, China |
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Abstract: | The Pearl River Mouth basin is one of the most important offshore basins in China. Petroleum exploration in the deep-water
area is to start in the Baiyun sag in the basin. Due to the high cost of exploration in deep-water areas, the hydrocarbon
migration and pressure evolution needs to be thoroughly probed before any actual exploration is to be done. Drilling results
have indicated that the pore pressure is hydrostatic in shallow-water area. The mud diapirs found in the Baiyun sag indicate
that there may be overpressure in the deep-water area. At present, little is known about hydrocarbon migration and pressure
distribution in deep-water areas. On the basis of geological data from wells and basin modeling, the research comes to the
following conclusions. (1) At least three episodic accumulations and releases of pressure had happened in the Cenozoic, which
were closely related to the three regional tectonic movements: the Zhu-Qiong movement in the Late Eocene, the Nanhai movement
in the Middle Oligocene and the Dongsha movement between the latest Middle Miocene and Late Miocene. The pressure release
and associated hydrocarbon migration occurred primarily during the Dongsha movement, when most of the overpressure was released
to hydrostatic pressure except for some overpressure in the deep-water area. (2) Both the measured pressure and the modeling
results indicate that the pore pressure is hydrostatic pressure in the shallow-water area. Abnormally high pressure in the
deep-water area is noted to be present. The difference of pressure distribution is caused by the lithologies, facies and faults.
(3) The diapirs in the deep water cannot be driven by the overpressure because the maximum pressure is less than 9.0 MPa in
the course of pressure evolution. (4) The fluids migrated to the shallow-water area and deep-water area along faults. Some
faults connected the deep-water fans with the hydrocarbon source. Huge oil and gas fields may be formed in the deep-water
area more favourably than in the shallow-water area.
Translated from Earth Science-Journal of China University of Geosciences, 2006, 31(2): 229–236 译自: 地球科学—中国地质大学学报] |
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Keywords: | pressure evolution overpressure 2D basin model hydrocarbon migration Baiyun sag Pearl River Mouth basin |
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