鄂尔多斯盆地上三叠统长7段泥页岩储集性能

Reservoir Quality Characterization of Upper Triassic Chang 7 Shale in Ordos Basin

页岩气的成功勘探开发引发了全球海相页岩研究的热潮,然而对处于生油窗内的陆相页岩储集性能的研究尚需加强.基于光学薄片、场发射扫描电镜、环境扫描电镜、纳米CT、图像分析、GRI物性、气体吸附等方法对长7段泥页岩储集性能进行系统研究.结果表明：长7段泥页岩形成于陆相半深湖-深湖环境,面积为10×104 km2,TOC〉2%,Ro=0.8%~1.0%,HI=124~480mg/g,生烃潜力高;脆性矿物含量为45%~59%,孔隙度为0.6%~3.8%,渗透率为0.000 72×10-3~0.002 30×10-3μm2;主要发育粒内孔、粒间孔和有机质孔,以伊蒙混层等粘土矿物粒内孔为主,有机质孔较少;孔隙直径为30~200nm,孔喉系统连通性中等,具备储集能力;伊蒙混层等粘土矿物含量与比孔容相关性优于热演化程度与烃指数等,表明长7页岩微观孔隙主要受控于成岩作用,有机质生烃作用对储集空间贡献相对较小;滞留烃主要以吸附态和游离态存在于黄铁矿晶间孔、伊蒙混层粒内孔、伊利石粒内孔与长石粒间孔.

The successful exploration and development of shale gas have triggered an upsurge of research in global marine shale.However,more reservoir quality research of non-marine shale in oil window is still needed.Reservoir quality potential of Upper Triassic Chang 7shale in Ordos basin was analyzed based on the data from thin section,FE-SEM,environmental SEM,nanoCT,GRI,and gas adsorption.Chang 7shale is deposited in semi-deep to deep lake,covering an area of 10×104 km2.Geochemical data suggests that Chang 7shale has potential of great hydrocarbon（HC）generation,with TOC2%,Ro =0.8%-1.0% and HI=124-480mg/g.The brittle mineral content is 45%-59%.The total porosity and permeability are0.6%-3.8%,0.000 72×10-3-0.002 30×10-3μm2 respectively.Three types of pores including interparticle pores,intraparticle pores and intra-organic matter（OM）pores are discovered,and intra-illite/smectite mix-layers pores dominate in the storage space,with small number of OM pores.The diameter of pores is 30-200 nm and the connectivity of pore system is medium to good,indicating that Chang 7shale is of the potential to become reservoir for shale oil.The pore volume is more related to illite/smectite mix-layers content than to that of maturity and hydrocarbon index,which may suggest that the porosity in Chang 7shale is controlled by diagenesis rather than HC generation.The residual HC is absorbed and distributed as free hydrocarbons in intra-pyrite pores,intra-illite/smectite mix-layer pores,intra-illite pores and inter-feldspar pores.