鄂尔多斯盆地东缘C-P煤系致密砂岩储层敏感性分析

鄂尔多斯盆地临兴地区上古生界致密砂岩储集层中矿物组成多样、孔隙结构复杂且黏土矿物含量高，直接影响储层改造和开发效果。文章基于X 衍射、铸体薄片、气测孔渗、压汞和敏感性实验，系统研究了储层敏感性及其影响因素。结果表明研究区砂岩中石英和岩屑含量高，长石含量较低，以岩屑砂岩、岩屑石英砂岩、长石岩屑砂岩和石英砂岩为主。黏土矿物主要为伊利石、高岭石、绿泥石以及伊/蒙混层；储层普遍低孔低渗，孔隙结构较差。速敏以太原组最强，山西组最弱，与伊利石+绿泥石含量正相关，高岭石含量负相关。水敏下石盒子组最强，太原组最弱，与伊/蒙混层含量正相关。盐敏与水敏有类似特点，与伊/蒙混层含量表现出正相关。酸敏山西组最强，下石盒子组最弱，与绿泥石和铁白云石矿物含量正相关。碱敏性山西组最强，太原组最弱，受长石、石英和高岭石含量影响。相关认识有助于指导研究区钻井、压裂等施工工艺选择和排采控制。

Sensitivity Analysis of Tight Sandstone Reservoirs of Carboniferous-Permian Coal-series in the Eastern Margin of the Ordos Basin

The Upper Paleozoic tight sandstone reservoirs in the Linxing area of the Ordos Basin show various rock and mineral compositions, complex pore structures, and high clay mineral contents, which directly affect the reservoir engineering and development. Based on X-ray diffraction, casting thin sections, gas porosity and permeability test, mercury intrusion porosimetry and sensitivity experiments, the reservoir sensitivity and its influencing factors were systematically investigated. The results show that the sandstones in the study area are of high contents of fragment quartz and lithic, while the feldspar content is low. The sandstones consist mainly of lithic, lithic quartz, feldspar lithic, and quartz sandstones. Clay minerals are mainly of illite, kaolinite, chlorite and illite/smectite (I/S)mixed layer. The reservoir properties are of low porosity and permeability, with poor pore structure. The sandstones of Taiyuan Formation show the strongest velocity sensitivity, while the Shanxi Formation sandstones are of the weakest, positively correlated with illite and chlorite content, while negatively correlated with kaolinite content. As for water sensitivity, the Xiashihezi Formation sandstones are the strongest while the Taiyuan Formation sandstones are the weakest, which are positively correlated with the I/S contents. The salt sensitivity is similar to water sensitivity, showing a positive correlation with I/S contents. The acid sensitivity of the Shanxi Formation sandstones is the strongest while the Xiashihezi Formation sandstones is the weakest, which is positively correlated with the contents of chlorite and ankerite. The alkali sensitivity is strong in the Shanxi Formation sandstones and weak in Taiyuan Formation sandstones, being associated with the contents of feldspar, quartz, and kaolinite. The results are helpful in guiding well drilling, fracturing and reservoir engineering processes, and also gas drainage controls.