Natural gas origin and accumulation characteristic of the Wen'an slope buried-hill belts in the Jizhong sub-basin, Bohai Bay basin

Natural gas origin and accumulation characteristic of the Wen'an slope buried-hill belts in the Jizhong sub-basin, Bohai Bay basin

Natural gas

Hydrocarbons

Petroleum reservoir engineering

Petroleum reservoirs

Gases

Exploratory geochemistry

Rocks

Isotopes

Mineralogy

The natural gas in the Wen'an slope buried-hill belts, Jizhong sub-basin has become an important target area for the deep and ultra-deep reservoir explorations in the Bohai Bay basin. However, the gas sources, charging history and gas accumulation process lack systematic research. In this paper, the identification of gas origin and source is conducted based on the chemical and stable carbon isotopic compositions, rare gas isotopic compositions and light hydrocarbons. The fluid inclusions analysis is applied to reveal the charging history and a gas accumulation model is established. Finally, the differences in the gas accumulation from three belts are compared. The results show that the natural gas in the inner belt is high-mature oil-associated gas, mainly derived from Es4+Ek source rock, and the gas reservoirs have experienced two different maturity of natural gas filling process. The natural gas in the middle belt is coal-derived gas, mainly derived from the C-P coal-measure source rocks, mixed some gases from Es4+Ek source rock, and the gas reservoirs have the characteristics of two different maturity of hydrocarbon fillings. The gases in the outward belt are biothermal-catalyzed transition zone gases at low maturity stage through oxidation modification. A comprehensive analysis of the Wen'an slope buried-hill belts is used to develop a model of "dual source hydrocarbon supply-fault unconformity transport-zoning difference accumulation", which developed into three types of reservoirs in the three belts: one-way single-source hydrocarbon-supply, stratified high-over-mature gas reservoirs

two-way two-source hydrocarbon-supply, fault-corrosion blocked mature to highly mature oil-gas reservoirs

and one-way single-source hydrocarbon-supply, stratified low-mature/biological gas reservoirs. 2022, Science Press. All right reserved.

1434-1446

4

96

Dizhi Xuebao/Acta Geologica Sinica

2022

Tian, Jianzhang

Zhang, Ruifeng

Li, Xiaodong

Wang, Xin

Zeng, Ting

Luo, Jing

Zhao, Meihong

Lu, Shan

Pan, Qinghua

Jiao, Yaxian

Mao, Chonghao

journalArticle

15717

10.19762/j.cnki.dizhixuebao.2021063