摘要
通过对鄂尔多斯盆地华池地区三叠系长7段钻井岩心进行岩石学特征以及元素地球化学测试分析,采用V/(V+Ni),Ni/Co,U/Th,Sr/Cu,CaO/(MgO*Al_(2)O_(3)),Sr/Ba,Fe/Mn,Mn/Ti,Ba_(bio)值和P/Al值等多种判别标准,并结合总有机碳的含量,进行古环境分析,恢复了沉积期的古气候、古盐度和古氧化还原条件等。研究结果表明:①鄂尔多斯盆地华池地区三叠系长7段岩石主要为深灰色泥岩、深灰色灰质泥岩及含炭屑的粉砂质泥岩、富含有机质的粉砂质泥岩,黏土矿物晶间孔与粒间孔是主要的孔隙类型,可见少量溶蚀孔和微裂缝。②研究区延长组长7沉积时期,有机质生产力强,环境以淡水为主且处于贫氧到缺氧状态,其中长7_(2)—长7_(3)亚段沉积时期,部分水体较深的区域出现极强的还原条件,主要为温湿气候。整体上为深水环境,长7_(2)亚段沉积时位于深水区的边界地带,其水深明显较长71与长7_(3)亚段更深,P/Al值以及Ba_(bio)值总体上变化趋势一致,自下而上具有逐渐增大的趋势。③研究区延长组长7段古沉积环境具备适宜的温度和盐度条件,与深水和强还原性特征共同促进了有机质的广泛发育、富集和保存,源岩与储层之间通过裂缝连通,离源岩较近的储层,其捕获原油的数量和效率更高,这种源储配置为页岩油的大规模富集成藏奠定了坚实的基础。
Through the petrological characteristics and elemental geochemical testing and analysis of cores from Triassic long 7-layer drilling in Huachi area of Ordos Basin,the paleoenvironmental characteristics were analyzed by using V/(V+Ni),Ni/Co,U/Th,Sr/Cu,CaO/(MgO*Al_(2)O_(3)),Sr/Ba,Fe/Mn,Mn/Ti,Ba_(bio)values and P/Al values,combined with the content of total organic carbon,to analyze the paleoenvironmental.Paleoenvironmental characteristics such as Ancient climate,paleosalinity and paleoredox conditions.The results show that:(1)The rocks of Triassic Chang 7 member in Huachi area of Ordos Basin are mainly dark gray mudstone,dark gray gray mudstone,silty mudstone containing carbon debris and silty mudstone rich in organic matter.Intercrystalline pores and intergranular pores of clay minerals are the main pore types.In addition,a small number of dissolution pores and fine fractures can be seen.(2)In the study area,the organic matter productivity was significant during the deposition period of Chang 7,and the environment was mainly freshwater with low oxygen content,which was in a state of poor oxygen to hypoxia,while in the Chang 7_(2) and 7_(3) periods,some areas with deep water bodies had extremely strong reduction conditions,mainly warm and humid climate.Overall,it indicates a deep-water environment.And Chang 7_(2) is located in the boundary zone of the deep-water area,and its water environment are obviously different from the adjacent Chang 71 and Chang 7_(3) members,showing relatively low water depth conditions.The P/Al value and Ba_(bio)value generally change in the Chang 7 member,from Chang 7_(3) to Chang 71,they all show a process of increasing from bottom to top.(3)The paleosedimentary environment of the Chang 7 member in this area has suitable temperature and salinity conditions,coupled with the deep water and strong reduction,which jointly promote the extensive development,enrichment and preservation of organic matter.The source rock and the reservoir are interconnected through fractures,and the oil generated in the source rock is more easily transported to the reservoir layer through fractures.In addition,when the distance between the source rock and the reservoir is relatively close,the process of crude oil migration and accumulation will be more efficient,and finally form a high-quality source rock system.Source rock and reservoir configuration laid a solid foundation for large-scale enrichment of shale oil and created extremely favorable conditions.
作者
梁锋
曹哲
LIANG Feng;CAO Zhe(Wuqi oil production plant of Yanchang Oilfield Co,Ltd,Yan’an 717600,Shaanxi,China)
出处
《岩性油气藏》
CAS
北大核心
2025年第1期24-40,共17页
Lithologic Reservoirs
关键词
页岩油储层
元素地球化学
古环境
古生产力
有机质富集
源储配置
长7
三叠系
华池地区
鄂尔多斯盆地
shale oil reservoir
elemental geochemistry
paleoenvironment
paleoproductivity
organic matter enrichment
source rock and reservoir configuration
Chang 7 member of Yanchang Formation
Triassic
Huachi area
Ordos Basin
