沉积学报2025，Vol.43Issue(4)：1251-1263,13.DOI:10.14027/j.issn.1000-0550.2024.085
纹层状页岩微观储层特征研究
Microscopic Reservoir Characteristics of Laminated Shales:A case study of the Wulalike Formation at the western margin of the Ordos Basin
摘要
Abstract
[Objective]This study examines the microscopic characteristics of laminated shale reservoirs in the Third member of the Middle Ordovician Wulalike Formation at the western margin of the Ordos Basin,to further understand their effectiveness.[Methods]An integrated approach combining X-ray diffraction(XRD),scanning electron microscopy(SEM),mineral mapping,organic geochemical analysis,CO2 and N2 adsorption and mercury injection capillary pressure tests to compare the mineralogy,organic geochemistry and pore structures of different tex-tures within the laminated shales.[Results]These laminated shales comprise limestone and tuff laminae and silica-rich beds.The limestone and tuff laminae(density of 60-180/m)have lower organic carbon content than the silica-rich beds.The laminated shales contain both pores and fractures.Clay mineral-related intergranular and intragranular pores are abundant in the silica-rich beds,with rare organic pores.Calcite and dolomite intragranular dissolution pores are predominant in the limestone laminae.The tuff laminae contain pyrite intercrystalline pores,clay-related in-tergranular and intragranular pores and dolomite intragranular dissolution pores.Dissolution pores in carbonate miner-als in the limestone and tuff laminae are related to dissolution of acid fluids generated by thermal evolution of organic matter in the silica-rich beds.Near-horizontal fractures are evident along boundaries between limestone and tuff lami-nae and silica-rich beds.The density of near-horizontal fractures is 63-130/m,and they are 0.2-4.9 mm wide.Lime-stone and tuff laminae have fewer micropores but more macropores than the silica-rich beds.Limestone laminae con-tain 2.5-4.3 times the volume of macropores,and these contribute 1.9-2.1 times the total pore volume found in adja-cent silica-rich beds.The volume of macropores in the tuff laminae is 1.5-2.3 times greater than in adjacent silica-rich beds.[Conclusions]In laminated shale reservoirs,oil and gas generated in silica-rich beds migrate along pores and fractures,and preferentially enrich in adjacent limestone and tuff laminae.Limestone and tuff laminae contain more macropores and more free gas than silica-rich beds.The laminated shale reservoirs in the Wulalike Formation contain a high proportion of free gas related to limestone and tuff laminae.关键词
鄂尔多斯盆地/乌拉力克组/页岩气/纹层状页岩/孔隙类型/孔隙结构Key words
Ordos Basin/Wulalike Formation/shale gas/laminated shales/pore type/pore structure分类
天文与地球科学引用本文复制引用
黄正良,王璐,曹斌风,刘洋,罗晓容,闫伟,马占荣,程明,俞雨溪,于洲..纹层状页岩微观储层特征研究[J].沉积学报,2025,43(4):1251-1263,13.基金项目
中国石油长庆油田公司科技重大专项(ZDZX2021-05)Science and Technology Major Project of PetroChina Changqing Oil-field Company,No.ZDZX2021-05 （ZDZX2021-05）
