摘要
渤海湾盆地济阳坳陷古近系和新近系浅层天然气资源丰富,但对于其成因及来源却一直都存在着争议。为了给该坳陷浅层天然气的勘探提供技术支撑,根据天然气的组分、轻烃指纹以及碳同位素值等测试资料,分析了该区浅层天然气的地球化学特征,明确了浅层天然气的成因类型,进而探讨了浅层天然气的来源。研究结果表明:①济阳坳陷浅层天然气的组分以甲烷为主,干燥系数高(超过95%),属于典型的干气;②轻烃中的正构烷烃含量低、异构烷烃含量高,表现为具有生物降解特征的油型气;③甲烷碳同位素值偏轻(-55.7‰^-42.3‰),乙烷、丙烷碳同位素值出现倒转,同时CO2碳同位素值偏重,具有典型原油降解气特征以及湿气组分改造的特征。结论认为:①该坳陷浅层天然气为生物成因和热成因改造而形成的混合次生气,是常规油藏生物降解的产物,由原油降解气和油溶释放气组成,并且原油降解气所占比例超过60%;②稠油区的浅层气应作为该坳陷天然气增储上产的重要勘探开发目标。
There are abundant Paleogene and Neogene shallow natural gas resources in the Jiyang Depression of the Bohai Bay Basin,but their genesis and sources have been controversial.In order to provide theoretical support for the exploration of shallow natural gas in the Jiyang Depression,this paper analyzed the geochemical characteristics of shallow natural gas in this area based on the test data of gas compositions,light hydrocarbon fingerprints and carbon isotopes.Then,the genetic types of shallow natural gas were determined.Finally,the sources of shallow natural gas were discussed.And the following research results were obtained.First,shallow natural gas in the Jiyang Depression is mainly composed of methane and its dry coefficient is high(over 95%),so it is classified as typical dry gas.Second,light hydrocarbon has a low n-alkane content and high isoparaffin content,so it presents as oil-type gas with biodegradation characteristics.Third,The carbon isotopes of methane are lighter(-55.7‰--42.3‰),the carbon isotopes of ethane and propane are reversed,and the carbon isotopes of CO2 are heavier,so it has the characteristics of typical crude oil degradation gas and wet gas composition transformation.In conclusion,shallow natural gas in the Jiyang Depression is mixed secondary gas of biogenesis and thermogenetic transformation,which is the biodegradation product of conventional oil reservoirs.It is composed of crude oil degradation gas and oil-dissolved released gas,and the proportion of crude oil degradation gas is more than 60%.What’s more,shallow natural gas in heavy oil areas shall be taken as an important exploration and development target for reserves and production increase in the Jiyang Depression.
作者
高长海
张云银
王兴谋
GAO Changhai;ZHANG Yunyin;WANG Xingmou(Key Laboratory of Deep Oil and Gas,China University of Petroleum-East China,Qingdao,Shandong 266580,China;Geophysical Research Institute,Sinopec Shengli Oilfield Company,Dongying,Shandong 257000,China)
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2020年第5期26-33,共8页
Natural Gas Industry
基金
山东省自然科学基金面上项目“碎屑岩不整合储层成岩胶结作用及其对储层物性的影响”(编号:ZR2017MD028)
中国石油化工股份有限公司科技攻关项目“盆缘稠油与浅层气成生关系及勘探方法”(编号:P15084)。
