生物气研究现状与勘探前景

Research status and exploration potential of biogenic gas

综合论述了生物气的特征及其研究进展,着重探讨了生物气成因、地球化学特征、勘探研究现状、生物气形成机制和控制因素,并介绍了生物气系统概念和特征,最后叙述了生物气藏的分布和我国生物气藏的远景。生物气是在还原环境的生物化学作用带内有机质为厌氧微生物所分解的最终产物,它以甲烷为主,并含部分二氧化碳及少量氮气和其它微量气体组分,生物甲烷气δ13C1值一般小于-55‰。生物甲烷气的形成途径主要有乙酸发酵和CO2还原2种类型。生物气生成与其所处的沉积环境、古气候、有机质的类型和丰度、水介质性质、地质作用、沉积时间等众多因素密切相关。生物气埋藏浅,分布广泛,一般存在于三角洲、大陆架和部分陆相沉积环境中,储层时代主要为白垩纪、古近纪、新近纪和第四纪。白垩纪的储量最丰富,古近纪、新近纪次之,第四纪生物气藏的规模一般较小。我国生物气勘探研究历史虽然不长,但生物气资源量丰富,具有良好的勘探前景。

This paper summarizes the characteristics and research progress of biogenic gas, with an emphasis on the genesis, geochemical characteristics, exploration and research status, formation mechanism and controlling factors of biogenic gas. It introduces the concept and characteristics of the biogenic gas system, and finally describes the distribution of biogenic gas pools and prospectivity of biogenic gas in China. Biogenic gas is the final product of the degradation of organic matter by anaerobic microorganisms in the biochemical process zone of deoxidization environment. It mainly consists of methane, and also contains some carbon dioxide and tiny amounts of nitrogen and other trace gases. The δ^13Cl values for the biogenic methane gas are generally lower than -55‰ .Biogenic methane gas mainly results from acetate fermentation and carbon dioxide reduction. Formation of the biogenic gas is affinitive with depositional environment, paleoclimate, types and abundance of organic matter, water medium＇s characteristics, geological process and depositional time. Biogenic gas is shallowlly burried and widely distributed. Biogenic gas pools are developed in delta, continental shelf and continental depositional environments. The geological ages of reservoirs are Cretaceous, Paleogene, Neogene and Quaternary. In terms of reserves, the Cretaceous is the most important and followed by the Paleogene and the Neogene. The Quaternary biogenic gas pools are generally of small sizes. Exploration and study history of biogenic gas in our country is not long, but biogenic gas resources are abundant, and their exploration potential is encouraging.