基于岩石薄片、铸体薄片以及扫描电镜等资料，对鄂尔多斯盆地陇东地区延长组长 4+5 致密砂岩储层的成岩作用特征进行了研究，并明确了镇原、环县、华池和白豹等地区储层致密化的成因机制。 结果表明：鄂尔多斯盆地陇东地区延长组长 4+5 储层的岩石类型主要为极细—细粒岩屑质长石砂岩、长石质岩屑砂岩以及两者之间的过渡类型，岩屑类型包括塑性易变形岩屑和刚性易溶岩屑，并且塑性易变形的云母碎屑含量高，导致储层抗压实能力差；在华池—白豹地区，颗粒表面绿泥石包膜对石英和长石的次生加大均起到有效抑制作用，含铁碳酸盐胶结强烈，并且长石溶蚀相对较弱；不同地区的成岩作用特征明显不同；储层的致密化受岩石成因类型、沉积物粒度、岩石组分及后期成岩改造等因素综合影响；在镇原—环县地区，延长组长 4+5 相对优质储层分布于石英加大不强烈的水下分支河道主砂体中，而在华池—白豹地区，延长组长 4+5 相对优质储层分布于适量绿泥石包膜发育的水下分支河道主砂体中。

Based on the observations of rock thin sections, casting thin sections and scanning electron microscope, this paper summarized the diagenesis characteristics of the tight sandstone reservoir of Chang 4+5 reservoir in Longdong area, and studied the origin of the tight reservoirs in Zhenyuan-Huanxian Region and Huachi-Baibao area. The result show that the rock types of Chang 4+5 reservoir mainly are very fine grained-fine grained lithic arkose, feldspathic lithic sandstone and the transition between the two types. The rock debris is mainly plastic and soluble. And the content of flexible mica fragments is high. The compressive strength of the reservoir rocks is very weak. The chlorite coating can effectively inhibit quartz and feldspar overgrowth in Huachi-Baibao area. The cementation of iron carbonate is intensive, and the feldspar dissolution is relatively weak. In different areas, the characteristics of diagenesis are obvious different. The tight sandstones of Chang 4+5 reservoir are contributed by genetic types of rock, sediment size, rock composition, late diagenetic reconstruction and so on. The high-quality reservoir rocks are those massive sandstones of the underwater distributary channels, with slight quartz overgrowth in Zhenyuan-Huanxian area and proper chlorite coating in Huachi-Baibao area.