摘要
洞庭盆地自然出露地表的天然气苗众多,预示盆地内可能具有比较丰富的浅层天然气资源。通过对洞庭盆地野外地质调查及对沅江县共华镇发现的天然气进行气体组成及同位素分析,显示天然气组分主要为CH_4,且不含C_2H_6以上的重烃,CH_4碳同位素值平均为-79.6‰,表现出典型的生物成因气特征。造成和兴村与宪成垸村天然气碳氢同位素值差异较大的原因可能是存在同位素分馏现象。根据CH_4的碳氢同位素值及CO_2的碳同位素值分布关系,判断该生物气为CO_2还原途径生成。推测全新世由于掀斜式构造沉降使江汉盆地大量硅藻随湖水流入洞庭盆地,为生物气的形成提供了丰富的物源及有利的沉积环境。洞庭盆地DQ1与DQ2浅井揭示了纵向上均为上细下粗的正韵律沉积序列,生物气的埋深极浅,分布于10～120m之间,为自生自储式组合类型。由于埋藏浅,开发成本低廉,如合理勘探、开发、利用,可造福一方地区。
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.
作者
钟洪洋
张道勇
肖明国
徐耀辉
Zhong Hong-yang;Zhang Dao-yong;Xiao Ming-guo;Xu Yao-hui(Key Laboratory of Exploration Techtiologies for Oil and Gas Resources ,Mitiislry of Education .Yangtze University , Wuhan 430100;Unconventional Oil and Gas Collaborative Innovation Centerin Hubei Province ,Yangtze University ,Wuhan 430100,China;Strategic Research Center of Oil andGas Resources,Ministry of Land and Resources,Beijing 100034 ,China;Hunafi HuashengEnergy Investment Development Co. Ltd.、Changsha 410004 ,China)
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2019年第3期361-369,共9页
Natural Gas Geoscience
基金
"十三五"全国油气资源评价(编号:2017YQZYPJ01)
国家自然科学基金项目(编号:41672117)
湖北省自然科学基金创新群体项目(编号:2017CFA027)联合资助
关键词
洞庭盆地
同位素分析
生物成因气
沉积环境
Dongting Basin
Isotopic analysis
Biogenic gas
Sedimentary environment
