琼东南盆地松南-宝岛凹陷北部断阶带油气来源与成藏时间  

A Study on Hydrocarbon Sources and Accumulation Time in the Northern Fault Zone,Songnan-Baodao Sag of Qiongdongnan Basin

作　　者：李兴 尤丽 詹冶萍 江汝峰 邓孝亮 胡斌 Li Xing;You Li;Zhan Yepin;Jiang Rufeng;Deng Xiaoliang;Hu Bin(Hainan Branch of CNOOC Ltd.,Haikou 570100,China)

机构地区：[1]中海石油(中国)有限公司海南分公司,海南海口570100

出　　处：《地球科学》2023年第8期3007-3020,共14页Earth Science

基　　金：中海石油(中国)有限公司科技项目“南海大中型天然气田形成条件、勘探潜力与突破方向”(No.KJZH-2021-0003-00)。

摘　　要：琼东南盆地松南-宝岛凹陷北部断阶带发现多个含气构造,对该区带油气来源等认识存在很大争议,深水区烃源岩规模研究方面还比较薄弱,阻碍了下一步勘探方向的决策.采集了研究区共84个泥岩、7个天然气、3个原油样品进行岩石热解、干酪根同位素、生物标志化合物、天然气轻烃与碳同位素等分析,系统对比研究区不同层系烃源岩地化特征,认为松南-宝岛凹陷北部断阶带油气来源于崖城组海相泥岩,以陆源有机质的生烃贡献最大.结合古环境、古生物与显微组分分析推测崖城组整体为浅海沉积,有利于好烃源岩的形成,在此基础上通过地震相的精细刻画厘清研究区崖城组烃源岩分布特征,结果表明研究区崖城组发育大规模煤系三角洲-浅海相沉积体系,其中前三角洲亚相、浅海相是好烃源岩主要赋存单元,烃源岩沿近凹断阶带分布.流体包裹体证据表明,松南-宝岛凹陷北部断阶带深水区至少存在两期烃类充注,主要成藏的是晚期高熟煤型气(7.8 Ma之后),证实煤系三角洲-浅海相沉积体系下发育的烃源岩能够为油气成藏提供充足的烃类,晚期更容易大量生成天然气,其东侧的深水区断阶带存在类似的烃源岩分布、热演化特征及输导体系,应是下一步天然气勘探首选.A number of gas-bearing structures were discovered in the northern fault zone of Songnan-Baodao Sag in Qiongdongnan Basin,but great disputes on the understanding of hydrocarbon source in the northern fault zone,the research on the scale of source rocks in deep-water is still weak,which hindered the decision of the next exploration direction.A total of 84 mudstone,7 natrual gases,3 crudoil samples from the study area were collected for rock pyrolysis,kerrogen carbon isotope,biomarkers,light hydrocarbon and carbon isotope analysis of natural gas in this paper,Geochemical characteristics of source rock from different strata in the study area systematic comparison,it is believed that the oil and gas in the norhern fault-step zone of Songnan-Baodao depression derived from marine mudstone of yacheng formation,and land-based organic hydrocarbon generation is dominant,combined with the paleoenvironment paleontology and microscopic components analysis,it is predicted that the whole yacheng formation is a shallow sea sedimentary environment,and conductive to the enrichment of organic matter form good source rocks,On this basis,the distribution characteristics of hydrocarbon source rocks of the yacheng formation in the study area are clarified through the seismic facies.The results show that the yacheng formation in the study area develop a large-scale coal-bearing delta、marine sedimentary system,which is the main occurrence unit of good hydrocarbon source rocks,distributed along the near concave and fault step zone.Fluid inclusion evidence shows that there are at least two stages of hydrocarbon filling in the deepwater area of the northern fault step zone of Songnan-Baodao depression,and the main accumulation is the high mature coal-type gas.It is confirmed that source rocks deposited on the coal-bearing delta and marine facies have rich gas supply,and a large amount of natural gas will be easier generated in the later stage,it is speculated that there are similar source rock distribution,thermal evolution characteristic

关 键 词：松南-宝岛凹陷 北部断阶带 海相烃源岩 煤系三角洲 陆源有机质 石油地质 

分 类 号：P618.13[天文地球—矿床学]