The pore–throat systems and physical properties of tight sandstone reservoirs are complex, and deposition is thought to be a fundamental control for them. In this study, the impacts of the full ranges of rock types (from pebbly coarse sandstone to fine sandstone) on the pore structures and physical properties of the Permian tight sandstone reservoir in the eastern Ordos Basin were investigated comprehensively through a series of experiments including conventional physical testing, thin-section analysis, scanning electron microscopy, nuclear magnetic resonance analysis and high-pressure mercury injection tests. The results showed that the coarser-grained sandstones tend to have higher feldspar content and lower percentage of cements, leading to strong dissolution, weak cementation and improved porosity and permeability. The medium sandstone has the highest level of quartz and the lowest average content of feldspar, resulting in strong heterogeneity of physical properties. Only those medium sandstone reservoirs with relatively high content of feldspars have better physical properties. Additionally, the coarser-grained sandstones contain relatively large dissolution pores (nearly 200 μm), whereas the finer-grained sandstones have more intercrystalline pores with a relatively more homogeneous pore structure. The pebbly coarse sandstone and coarse sandstone reservoirs are favorable targets with best physical properties.

中文翻译：

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岩石类型对西北鄂尔多斯盆地致密砂岩储层孔隙结构和物理性质的影响

致密砂岩储层的孔喉系统和物理性质很复杂，沉积被认为是对它们的基本控制。在这项研究中，通过一系列包括常规在内的实验，全面研究了整个岩石类型（从卵石粗砂岩到细砂岩）对鄂尔多斯盆地东部二叠系致密砂岩储层孔隙结构和物理性质的影响。物理测试，薄层分析，扫描电子显微镜，核磁共振分析和高压汞注入测试。结果表明，较粗粒的砂岩往往具有较高的长石含量和较低的水泥含量，从而导致强溶解性，弱胶结作用和改善的孔隙度和渗透率。中型砂岩的石英含量最高，长石的平均含量最低，因此物理性质具有很强的异质性。只有那些长石含量相对较高的中型砂岩储层才具有更好的物理性质。另外，较粗粒的砂岩含有相对较大的溶蚀孔（接近200μm），而较细粒的砂岩具有较多的晶间孔，且孔结构相对较均匀。卵石质粗砂岩和粗砂岩储层是物性最好的有利目标。另外，较粗粒的砂岩含有相对较大的溶蚀孔（接近200μm），而较细粒的砂岩具有较多的晶间孔，且孔结构相对较均匀。卵石质粗砂岩和粗砂岩储层是物性最好的有利目标。另外，较粗粒的砂岩含有相对较大的溶蚀孔（接近200μm），而较细粒的砂岩具有较多的晶间孔，且孔结构相对较均匀。卵石质粗砂岩和粗砂岩储层是物性最好的有利目标。