由于致密砂岩储层发育影响因素复杂,导致对储层进行合理、定量分类通常较困难。运用铸体薄片、扫描电镜、黏土矿物X-射线衍射、高压压汞、核磁共振等资料,对鄂尔多斯盆地东北部神木地区石炭系本溪组煤系致密砂岩气储层特征进行研究,采用储层综合指数(CEI)建立储层定量分类标准,预测有利储层。结果表明:神木地区本溪组主要发育石英砂岩和岩屑石英砂岩,填隙物主要为高岭石、绿泥石、铁白云石和铁方解石等胶结物;孔隙类型以原生粒间孔隙和高岭石晶间孔隙为主,微裂隙和岩屑粒内溶孔次之,主要发育粗孔-中喉型和细孔-小喉型孔隙结构;区内压实压溶作用和胶结作用普遍,石英及岩屑粒内溶蚀作用发育,储层普遍进入中成岩B期阶段。神木地区本溪组发育Ⅰ类(CEI>0.6)、Ⅱ类(0.4<CEI<0.6)和Ⅲ类(CEI<0.4)储层,Ⅰ类和Ⅱ类为有利储层,Ⅰ类储层分布范围相比Ⅱ类储层较小,但两者纵向上均以本1段最为发育,平面上多分布在水下分支河道和砂坪微相中。

Due to the complex factors affecting the development of tight sandstone reservoirs, it is usual- ly difficult to make reasonable and quantitative classification and evaluation for tight sandstone reser- voirs. The characteristics of tight sandstone gas reservoir of Carboniferous Benxi Formation in Shenmu area of Ordos Basin were analyzed by using the data of cast thin section, scanning electron microscope, clay mineral X - ray diffraction, high pressure mercury injection and nuclear magnetic resonance. The reservoir quantitative evaluation standard was established by using reservoir comprehensive evaluation index CEI, and the distribution area of favorable reservoir was predicted. The results show that quartz sandstone and lithic quartz sandstone are dominated in Benxi Formation in Shenmu area, and the inter- stitial fillings are main cements such as kaolinite, chlorite, iron dolomite and iron calcite, and the pore types are primary inter-granular pores and kaolinite inter-crystalline pores, followed by micro-fracture and inner-granular solution pores of cuttings. The pore structure is dominated by coarse pore-medium throat type and fine pore-small throat type. The compaction and cementation are common in the area, and the dissolution of quartz and cuttings are developed, reflecting the reservoir generally enters the B stage of middle diagenetic period. Three types of reservoirs including Type Ⅰ( CEI > 0. 6) , Type Ⅱ ( 0. 4 < CEI < 0. 6) , and Type Ⅲ( CEI < 0. 4) are developed in Benxi Formation in the Shenmu area, and the Type Ⅰ and Type Ⅱ are favorable reservoirs in the study area. The distribution range of Type Ⅰ reservoir is smaller than that of Type Ⅱ reservoir, but the two types of reservoirs all developed more in Member 1 of Benxi Formation, and mostly distributed in underwater branch channel and sand flat micro facies in plane.