Origin and evolution of overpressure in shale gas reservoirs of the Upper Ordovician Wufeng Formation–Lower Silurian Longmaxi Formation in the Sichuan Basin

被引：0

作者：

Tang L. ^{[1
,2
]}

Song Y. ^{[2
]}

Zhao Z. ^{[1
]}

Jiang Z. ^{[2
]}

Jiang S. ^{[3
]}

Chen X. ^{[1
]}

Li Z. ^{[2
]}

Li Q. ^{[3
]}

机构：

[1] Research Institute Co., Ltd. of CNOOC, Beijing

[2] Unconventional Oil & Gas Science and Technology Research Institute, China University of Petroleum - Beijing, Beijing

[3] Faculty of Earth Resources, China University of Geosciences - Wuhan, Hubei, Wuhan

来源：

Natural Gas Industry | 2022年 / 42卷 / 10期

关键词：

Burial–uplift; Expansion by hydrocarbon generation; Origin of overpressure; Overpressure evolution; Pressurization model; Sichuan Basin; Upper Ordovician Wufeng Formation–Lower Silurian Longmaxi Formation;

D O I：

10.3787/j.issn.1000-0976.2022.10.004

中图分类号：

学科分类号：

摘要：

Overpressure is common in the shale gas reservoirs of the Upper Ordovician Wufeng Formation–Lower Silurian Longmaxi Formation in the Sichuan Basin. However, the origin and evolution process of overpressure in shale gas reservoirs has not been understood clearly. In order to reveal the formation mechanism and evolution law of overpressure in the Wufeng Formation–Longmaxi Formation shale gas reservoirs, based on well logging, numerical simulation and Laser Raman experiments, the formation mechanism of overpressure in the Wufeng Formation–Longmaxi Formation was comprehensively identified, the dynamic evolution of overpressure during burial and uplift was verified by forward and inversion simulation, and the overpressure development model of the Wufeng Formation–Longmaxi Formation inside, margin and outside of basin were established. The following results were achieved. (1) Hydrocarbon generation pressurization is the formation mechanism of overpressure in the Wufeng Formation–Longmaxi Formation by well logging combination methods, Bowers method and acoustic velocity–rock density cross plot. (2) Hydrocarbon generation pressurization is closely related to the abundance and type of organic matter, original hydrogen index, kerogen mass fraction and conversion rate, oil cracking rate and residual hydrocarbon coefficient. (3) The formation pressure coefficient of the reservoir during kerogen oil-generating can reach 1.73 in the Wufeng Formation–Longmaxi Formation of the Jiaoshiba area, while it can reach 2.78 during oil gas-cracking by theoretical calculation. The pressurization contribution of oil gas-cracking is much greater than that of kerogen oil-generating. (4) The average capture pressure in the Wufeng Formation–Longmaxi Formation shale in the southern Sichuan Basin is 163.20 MPa and the average formation pressure coefficient is 2.51. (5) During the tectonic uplift in the Jiaoshiba area, the formation pressure decreased by 44.16 MPa, 40.28 MPa and 36.50 MPa respectively due to temperature drop, pore rebound and shale gas loss. It is concluded that the systematic study on the origin and evolution of overpressure is helpful in understanding the theory of differential enrichment and accumulation of shale gas, and is of great significance in guiding the selection and evaluation of favorable marine shale gas areas under the complex tectonic background in the Sichuan Basin and its surrounding areas. © 2022 Natural Gas Industry Journal Agency. All rights reserved.

引用

页码：37 / 53

页数：16

共 44 条

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