鄂尔多斯盆地镇北地区长4+5段储层特征及影响因素

利用岩心观察、薄片鉴定、扫描电镜、阴极发光、常规物性、压汞、测井等方法,研究鄂尔多斯盆地镇北地区上三叠统延长组长4+5段储层特征,并探讨其储集性影响因素。结果表明:镇北地区长4+5段储层岩性主要为岩屑长石砂岩或长石岩屑砂岩,储集空间以粒间孔和长石溶孔为主,孔隙结构为中-小孔微细喉型和细微孔微喉型,物性为低孔低渗特征。储集性控制因素与沉积微相、碎屑颗粒成分、成岩作用密切相关,河口坝、水下分流河道砂体孔渗性较好;陆源碎屑的组分、含量、特性为储层的发育以及后期成岩作用的改造奠定物质基础;成岩过程中压实、胶结为破坏性成岩作用,溶蚀、长石高岭石化、绿泥石环边为建设性成岩作用。镇北地区长4+5储层整体为低孔低渗特征,强烈的压实作用和胶结作用导致储层的致密化。

Characteristics and influential factors of Chang 4+5 reservoir of Zhenbei area in Ordos Basin,China

This paper studies the characteristics of Chang 4+5 reservoir of Upper Triassic Yanchang Formation in the Zhenbei area of Ordos Basin by core observation, sections, SEM, cathodoluminescence,physical property,mercury intrusion,logging and so on,and discusses the factors affecting the reservoir quality.The results show that the lithology of Chang 4+5 reservoir in the Zhenbei area is mainly lithic arkose or feldspathic litharenite,the main reservoir spaces are the intergranular pore and feldspar dissolved pore,and the types of pore structure are the middle-fine pore with fine throat and fine-microscopic pore with microscopic throat,and the physical property is low porosity and low permeability.The controlling factors of the reservoir are closely related with sedimentary microfacies,terrigenous clastic components and diagenesis.The sand bodies of the subaqueous distributary channel and mouth bar have better porosity and permeability. The composition,content and characteristics of the terrigenous detrital particles lay the material base for the development of the reservoir and the late diagenesis alteration.Compaction and cementation are the destructive diagenesis,while dissolution,kaolinization of feldspar and chlorite rim are the constructive diagenesis. The Chang 4+5 reservoir in the Zhenbei area as a whole has the characteristics of low porosity and low permeability,and the strong compaction and cementation leads to the tightness of the reservoir.