China Petroleum Exploration ›› 2025, Vol. 30 ›› Issue (2): 1-15.DOI: 10.3969/j.issn.1672-7703.2025.02.001

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Main controlling factors for the formation of deep to ultra-deep carbonate giant gas fields: a case study of Anyue and Penglai gas fields in Sichuan Basin

Wei Guoqi1,2,Zhang Benjian3,Xie Zengye1,2,Yang Wei1,2,Li Jian1,2,Cui Huiying1,2,Guo Jianying1,2,Wang Xiaobo1,2,Xie Wuren1   

  1. 1 PetroChina Research Institute of Petroleum Exploration & Development; 2 CNPC Key Laboratory of Natural Gas Reservoir Formation and Development; 3 Research Institute of Exploration and Development, PetroChina Southwest Oil & Gasfield Company
  • Online:2025-03-14 Published:2025-03-14

Abstract: In Sichuan Basin, two trillion-cubic-meter level giant gas fields, Anyue and Penglai gas fields, have been discovered in deep to
ultra-deep formations in the Sinian–Cambrian. It is urgent to clarify the main controlling factors for hydrocarbon accumulation to determine the replacement fields. Based on previous studies and combined with geological and geochemical data, a systematic study has been conducted on gas genesis and the main controlling factors for hydrocarbon accumulation in Anyue and Penglai gas fields. The study results conclude that the formation of deep to ultra-deep giant gas fields was mainly controlled by four factors: (1) Two intracontinental rifts were developed during the Late Sinian–Early Cambrian, namely Deyang–Anyue and Wanyuan–Dazhou rifts, developing high-quality source rocks in the Lower Cambrian, with a source rock thickness in the rifts 3–4 times and a gas generation intensity 2–3 times those in neighboring areas. (2) Anyue–Fengjie shelf-rimmed platform was formed during the Late Sinian–Early Cambrian, which controlled the formation of four sets of high-quality platform marginal mound beach or granular beach facies reservoirs, i.e., the second and fourth members of the Sinian Dengying Formation, lower member of the Cambrian Canglangpu Formation, and the Cambrian Longwangmiao Formation, with large thickness and good storage performance of platform marginal reservoirs. (3) The long-term inheritance and development of Gaoshiti–Moxi huge paleo-uplift formed during Tongwan movement stage controlled the formation of large structural–lithologic traps in the core of the paleo-uplift and lithologic traps in the slope zone, with areas of 7500 km2 and 5720 km2 of Dengying Formation trap groups. (4) The large ancient oil reservoirs cracked and insitu accumulation occurred, with high accumulation efficiency. A large number of liquid hydrocarbon inclusions were observed in various host minerals, with abundance of 10%–80%. The content of reservoir bitumen in gas-rich zone is high, mainly ranging in 1%–8%. Based on factors such as the development degrees of platform marginal mound beach body and intraplatform beach body, large-scale source rocks, structure of the target layer, and exploration degree, as well as geological conditions for stereoscopic hydrocarbon accumulation and composite enrichment, three types of favorable zones for the formation of large and giant gas fields have been proposed. Type Ⅰ zone includes platform marginal beach/intraplatform beach zone where Anyue and Penglai gas fields have been discovered. Type Ⅱ zone is the platform marginal beach/intraplatform beach development zone where breakthroughs have been made or has the potential for large-scale exploration, such as Hongya–
Leshan, Yilong–Guangyuan, Rongchang–Gulin, Bazhong–Dazhou, and Shizhu–Lichuan. Type Ⅲ zone is the intraplatform beach development zone, such as Chongqing–Liangping and Weiyuan–Luzhou. The study results have important reference significance for oil and gas exploration in deep to ultra-deep formations.

Key words: deep to ultra-deep formations, intracratonic rift, shelf-rimmed platform, main controlling factor, Sinian–Cambrian, Anyue Gas Field, Penglai Gas Field, Sichuan Basin

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