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鄂尔多斯盆地米脂地区上古生界盒8~上储层岩石类型主要为岩屑砂岩,少量为岩屑质石英砂岩和石英砂岩,个别为长石质岩屑砂岩。沉积相属于辫状河三角洲前缘沉积,砂岩平均孔隙度为5.85%,平均渗透率为0.54×10~(-3)μm~2,属低孔低渗透储层。综合运用薄片鉴定、扫描电镜、压汞和包裹体测温等手段对成岩作用类型及其对储层物性的影响进行了研究,判别出了成岩阶段及成岩序列。研究区储层为晚成岩B期,成岩作用类型包括压实作用、胶结作用、交代作用和溶蚀作用,机械压实作用、化学压溶作用和自生矿物的胶结作用是造成储层低孔低渗透的主要原因,成岩晚期的溶蚀作用大大改善了储层物性。
The Upper Jurassic Box 8 ~ Upper reservoir rock types in Mizhi area, Ordos Basin are mainly lithic sandstone, a small amount is lithic quartzite sandstone and quartz sandstone, and some are feldspathic lithic sandstone. Sedimentary facies belong to the front of braided delta. The average porosity of sandstone is 5.85% and the average permeability is 0.54 × 10 ~ (-3) μm ~ 2. It belongs to low porosity and low permeability reservoir. The types of diagenesis and its influence on reservoir physical properties were studied by means of thin slice identification, scanning electron microscopy, mercury intrusion and temperature measurement of inclusions. Diagenesis and diagenetic sequences were identified. The reservoirs in the study area are late-diagenetic B stage. Diagenesis types include compaction, cementation, metasomatism and dissolution, mechanical compaction, chemical pressure-dissolving and cementation of authigenic minerals, resulting in low porosity and low permeability of reservoir The main reason for the late diagenetic dissolution has greatly improved reservoir physical properties.