鄂尔多斯盆地三叠纪湖盆东部“边缘”长7段烃源岩的发现及其地球化学特征  

Discovery and geochemical characteristics of Chang 7 source rocks from the eastern margin of a Triassic lacustrine basin in the Ordos Basin

作　　者：韩载华 赵靖舟 孟选刚[3] 沈振振[3] 杨荣国 张恒[3] 高飞龙 HAN Zaihua;ZHAO Jingzhou;MENG Xuangang;SHEN Zhenzhen;YANG Rongguo;ZHANG Heng;GAO Feilong(School of Earth Sciences and Engineering,Xi’an Shiyou University,Xi’an,Shaanxi 710065,China;Shaanxi Key Laboratory of Petroleum Accumulation Geology,Xi’an Shiyou University,Xi’an,Shaanxi 710065,China;Qilicun Oil Production Plant,Yanchang Oil Field Corporation,Yan’an,Shaanxi 717100,China)

机构地区：[1]西安石油大学地球科学与工程学院,西安710065 [2]西安石油大学陕西省油气成藏地质学重点实验室,西安710065 [3]延长油田股份有限公司七里村采油厂,陕西延安717100

出　　处：《石油实验地质》2020年第6期991-1000,共10页Petroleum Geology & Experiment

基　　金：国家科技重大专项(2016ZX05050)资助。

摘　　要：以往对鄂尔多斯盆地三叠系主力烃源岩的研究主要集中于盆地内部的湖盆中心及其周围地区,对湖盆“边缘”特别是东缘地区的烃源岩则鲜有研究。为弥补以往研究的空白,解决鄂尔多斯盆地东缘三叠系是否发育有效烃源岩这一问题,选择七里村油田为研究区,通过岩心观察、测井曲线特征分析、地化测试分析等手段,对该油田三叠系长7段烃源岩特征进行了详细研究。七里村油田长7段烃源岩分布范围广,面积超过2500 km^2;可分为黑色泥页岩和暗色泥岩2种类型,平均厚度分别为9.2 m和28.9 m;烃源岩有机质丰度高,黑色泥页岩TOC含量平均为2.73%,可达到“最好”烃源岩标准,暗色泥岩TOC含量平均为1.98%,达到“中等—好”烃源岩标准;有机质类型总体为Ⅰ—Ⅱ1型,以生油为主;多项成熟度参数表明黑色泥页岩和暗色泥岩成熟度无明显差别,均已达到成熟,处于主要生油阶段。根据烃源岩生物标志化合物特征,分析其沉积环境为陆相淡水还原环境,且黑色泥页岩所处沉积环境还原性比暗色泥岩更强;烃源岩母质来源主要为低等水生生物,其次为陆源高等植物;暗色泥岩较黑色泥页岩有更多陆源高等植物的贡献。综合分析认为,鄂尔多斯盆地东缘七里村油田长7段烃源岩是本地区油藏的主力烃源岩,而且优质烃源岩的发现表明本区长7段页岩油和致密油也具有良好勘探前景。Previous studies of source rocks in the Triassic Yanchang Formation in the Ordos Basin were mainly focused on the inner part of the basin,especially on the depocenter and its surrounding areas.Few investigations have been made with regard to source rocks on the“margin”of the lacustrine basin,particularly on the eastern margin.In order to make up for the limitations of previous work and determine whether effective source rocks are developed on the eastern margin of the Ordos Basin,we chose the Qilicun Oilfield in Yanchang County as our study area.The characteristics of the Chang 7 source rocks from the Qilicun Oilfield were studied through core observations,logging curve analyses and geochemical tests.The Chang 7 source rocks in the Qilicun Oilfield were widespread,with an area of over 2500 km^2.They were subdivided into two types:black shale and dark mudstone,averaging 9.2 m and 28.9 m thick,respectively.The average TOC content of the black shale is 2.73%,which is in accordance with the“best”source rock standard.The average TOC content of the dark mudstone is 1.98%,which falls into the“good”source rock category.The organic matter is of types Ⅰ-Ⅱ1,mainly generating oils.Maturity parameters show that there is no significant difference between the black shale and the dark mudstone,and both have entered the main oil generation stage.Biomarker analyses indicate that the Chang 7 source rocks were deposited in continental fresh water in a reducing environment.The black shale depositional environment was more reducing than that of the dark mudstone.The source organic matter is mainly derived from lower ranked aquatic organisms,with some higher land plants.Compared with the black shale,the dark mudstone has more contribution from terrestrial higher plants.The Chang 7 source rocks from the Qilicun Oilfield on the eastern margin of the Ordos Basin is the major source rock for hydrocarbon accumulation in this area.Moreover,the discovery of good quality source rocks suggests that the Chang 7 section on the eas

关 键 词：烃源岩 地球化学特征 延长组 七里村油田 鄂尔多斯盆地 

分 类 号：TE122.11[石油与天然气工程—油气勘探]