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Title: Identifying potential gas accumulation sites from Oligocene overpressure data in the Qiongdongnan basin, offshore South China

Abstract

Overpressure in Oligocene formations in southern Qiongdongnan basin, offshore China, can be determined either by actual measurements in wells or by calculations using data derived from well logs and seismic surveys. The overpressure is mainly the result of undercompaction of Oligocene rocks during rapid loading by Pliocene and Quaternary sedimentation and of the subsequent thermal expansion of fluids in the Oligocene strata. Every formation possesses its own normal compaction trend (plot of shale-interval acoustic transit times vs. depth). The actual fluid pressures and potential pressures can be computed by the equilibrium-depth method. This method must be corrected for the thermal expansion of fluid. The pressure corrections are based on shale-interval transit times from well logs, interval velocities interpreted from vertical seismic profile (VSP) surveys, and stacking velocity from sonic log data of nearby wells. Gas generated from source rocks is assumed to have moved vertically from strata of higher hydraulic pressure potential to those of lower potentials and to have moved laterally and accumulated within areas where the contour closures of a gas equipotential hydraulic-pressure surface (U curves) have lower values. In the study area, the vicinity of the Yacheng gas field, the potential maps (U, gas, and V, water,more » maps) and hydraulic head profiles can be plotted from values derived either from actual pressure measurements or from calculations. These maps and profiles show prospective areas of gas accumulation. 5 refs., 10 figs., 1 tab.« less

Authors:
 [1]
  1. Nanhai West Oil Corp., Guangdong (China)
Publication Date:
OSTI Identifier:
6418363
Resource Type:
Journal Article
Journal Name:
AAPG Bulletin (American Association of Petroleum Geologists); (United States)
Additional Journal Information:
Journal Volume: 77:5; Journal ID: ISSN 0149-1423
Country of Publication:
United States
Language:
English
Subject:
03 NATURAL GAS; CHINA; OFFSHORE SITES; NATURAL GAS DEPOSITS; EXPLORATION; RESOURCE POTENTIAL; FLUIDS; MAPS; PRESSURE MEASUREMENT; SEISMIC SURVEYS; SOURCE ROCKS; ASIA; GEOLOGIC DEPOSITS; GEOPHYSICAL SURVEYS; MINERAL RESOURCES; RESOURCES; SURVEYS; 030200* - Natural Gas- Reserves, Geology, & Exploration

Citation Formats

Funing, Liu. Identifying potential gas accumulation sites from Oligocene overpressure data in the Qiongdongnan basin, offshore South China. United States: N. p., 1993. Web. doi:10.1306/BDFF8D8A-1718-11D7-8645000102C1865D.
Funing, Liu. Identifying potential gas accumulation sites from Oligocene overpressure data in the Qiongdongnan basin, offshore South China. United States. https://doi.org/10.1306/BDFF8D8A-1718-11D7-8645000102C1865D
Funing, Liu. 1993. "Identifying potential gas accumulation sites from Oligocene overpressure data in the Qiongdongnan basin, offshore South China". United States. https://doi.org/10.1306/BDFF8D8A-1718-11D7-8645000102C1865D.
@article{osti_6418363,
title = {Identifying potential gas accumulation sites from Oligocene overpressure data in the Qiongdongnan basin, offshore South China},
author = {Funing, Liu},
abstractNote = {Overpressure in Oligocene formations in southern Qiongdongnan basin, offshore China, can be determined either by actual measurements in wells or by calculations using data derived from well logs and seismic surveys. The overpressure is mainly the result of undercompaction of Oligocene rocks during rapid loading by Pliocene and Quaternary sedimentation and of the subsequent thermal expansion of fluids in the Oligocene strata. Every formation possesses its own normal compaction trend (plot of shale-interval acoustic transit times vs. depth). The actual fluid pressures and potential pressures can be computed by the equilibrium-depth method. This method must be corrected for the thermal expansion of fluid. The pressure corrections are based on shale-interval transit times from well logs, interval velocities interpreted from vertical seismic profile (VSP) surveys, and stacking velocity from sonic log data of nearby wells. Gas generated from source rocks is assumed to have moved vertically from strata of higher hydraulic pressure potential to those of lower potentials and to have moved laterally and accumulated within areas where the contour closures of a gas equipotential hydraulic-pressure surface (U curves) have lower values. In the study area, the vicinity of the Yacheng gas field, the potential maps (U, gas, and V, water, maps) and hydraulic head profiles can be plotted from values derived either from actual pressure measurements or from calculations. These maps and profiles show prospective areas of gas accumulation. 5 refs., 10 figs., 1 tab.},
doi = {10.1306/BDFF8D8A-1718-11D7-8645000102C1865D},
url = {https://www.osti.gov/biblio/6418363}, journal = {AAPG Bulletin (American Association of Petroleum Geologists); (United States)},
issn = {0149-1423},
number = ,
volume = 77:5,
place = {United States},
year = {Sat May 01 00:00:00 EDT 1993},
month = {Sat May 01 00:00:00 EDT 1993}
}