摘要
在川东北地区石油地质背景特征的基础上,探讨了元坝与河坝地区陆相储层天然气的成因。元坝地区侏罗系储层天然气重烃气体含量较高;多数样品甲烷δ^(13)C和δD值分别在-42.2‰^-34.4‰和-208‰^-168‰,乙烷δ^(13)C值在-31.4‰^-21.4‰,甲烷δ^(13)C和δD值之间相关性好;天然气主要来源于侏罗系自流井组或千佛崖组陆相烃源岩。元坝地区须家河组储层天然气重烃气体含量低;甲烷δ^(13)C和δD值分别为-31.7‰^-29.2‰和-170‰^-148‰,乙烷δ^(13)C值在-27.7‰^-26.5‰;天然气主要来源于元坝地区上三叠统须家河组高-过成熟的腐殖型烃源岩。元坝地区陆相储层天然气成因的主控因素是陆相烃源岩发育及其成熟度。河坝地区陆相储层天然气重烃气体含量变化大;甲烷δ^(13)C值大多重于-32‰,甲烷δD值分布范围较大,在-1δ6‰^-122‰,乙烷δ^(13)C值在-33.2‰^-29 6‰;甲烷δD与δ^(13)C值之间相关性很差,部分样品甲烷与乙烷的δ^(13)C值倒转,表明河坝地区陆相储层天然气成因复杂,有来源于陆相须家河组的天然气,也有来源于海相烃源岩的天然气,以及海相与陆相来源天然气的混合气。河坝地区陆相储层天然气成因的主控因素是海相与陆相多套烃源岩与不同级别断裂。陆相储层天然气中CO_2的δ^(13)C值多轻于-12‰,属于有机质热分解成因。稀有气体~3He/~4He比值在0.003 3R_a^0.018 1R_a,分布于地壳来源或放射性成因的范围内,表明天然气中没有幔源稀有气体的贡献。
The origin of natural gas in terrestrial reservoirs of Yuanba and Heba regions is investigated by analyzing the geochemi- cal characteristics of natural gases and surveying the regional background of petroleum geology in the northeastern Sichuan Basin, China. Results show that.. 1） In Yuanba region, natural gases from the Jurassic clastic rock reservoirs contain high levels of heavy hydrocarbon gases. The δ13C and 3D values of methane respectively range from - 42.2‰ to - 34.4‰ and - 208‰ to - 168‰, whereas the δ13C values of ethane range from -31.4‰ to -21.4‰ in most gas samples. There isastrongcorrela- tion between the δ13C and 3D values of methane in gas samples tested, and the gases are mainly originated from terrestrial source rocks of the Jurassic Ziliujing and Qianfoya Formation. Differently, natural gases from the Xujiahe Formation contain low levels of heavy hydrocarbon gases; theδ13 C and 3D values of methane in natural gas samples respectively range from - 31. 7‰ to -29. 2‰ and - 170‰ to - 148‰, whereas the δ13C values of ethane range from - 27. 7‰ to - 26. 5‰. The gases are mainly originated from high-to-over-maturity humic terrestrial source rocks of the Upper Triassic Xujiahe Formation. The origin of natural gases is mainly controlled by the development of terrestrial source rocks and their maturity. 2） In Heba region, natural gases from the terrestrial reservoirs contain varying levels of heavy hydrocarbon gases. The δ13C values of methane are mostly greater than - 32.0‰ and the corresponding 3D values widely range from - 186‰ to - 122‰ ; the δ13C values of ethane range from - 33. 2‰ to - 29.6‰. There is a poor correlation between theδ13C and 3D values of methane in gas samples. Theδ13C values of methane and ethane are reversed in a few cases, suggesting the complex origin of the gases that include those from ter- restrial source rocks of the Xujiahe Formation and marine source rocks, as well as mixed gases from the above two origins. The development of
出处
《石油学报》
EI
CAS
CSCD
北大核心
2014年第1期26-36,共11页
Acta Petrolei Sinica
基金
国家重点基础研究发展计划(973)项目(2012CB214801)
中国科学院重要方向项目(KZCX2-YW-Q05-03)资助
关键词
川东北
陆相储层
天然气成因
碳同位素
氢同位素
稀有气体同位素
northeastern Sichuan Basin
terrestrial reservoir
natural gas genesis
carbon isotope
hydrogen isotope
noble gas i- sotope
