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- Title
洞庭盆地第四系极浅层天然气成因类型及地质意义.
- Authors
钟洪洋; 张道勇; 肖明国; 徐耀辉
- Abstract
There are many natural gas seepages on the surface of Dongting Basin, indicating that there may be abundant shallow gas resources in this basin. By analyzing the composition and isotope of nature gas collected from Gonghua town, Yuanjiang county during field geological investigation in Dongting Basin, it was discovered that this natural gas belonged to biogenic gas. The main composition of this natural gas was methane, without other alkane gases. Moreover, the average carbon isotopic ratio of methane was-79.6‰. The reason for the difference in carbon isotope and hydrogen isotope of natural gas between villages of Hexing and Xianchengyuan may be due to the isotope fractionation. It was concluded that the biogas formed through the pathway of carbon dioxide reduction on the basis of the distribution relation of carbon isotopes of methane and carbon dioxide. We speculated that a large number of diatoms from Jianghan Basin flowed into Dongting Basin with lake water due to the tilted tectonic subsidence during Holocene, which provided abundant material source and favorable sedimentary environment for the formation of biogas. The data of Wells DQ1 and DQ2 in Dongting Basin all presented positive rhythmic sedimentary sequence of upper and lower coarse in vertical direction. Biogas has a very shallow depth and is usually distributed between 10 and 120 meters. Moreover, its type is generally positive reservoir-forming combination of authigenic and self-accumulation type. If biogas could be properly explored, developed, and utilized, it would benefit one area due to its shallow burial depth and low development costs.
- Subjects
GAS seepage; CARBON dioxide reduction; NATURAL gas; HYDROGEN isotopes; CARBON isotopes; ISOTOPIC fractionation
- Publication
Natural Gas Geoscience, 2019, Vol 30, Issue 3, p361
- ISSN
1672-1926
- Publication type
Article
- DOI
10.11764/j.issn.1672-1926.2018.10.004