鄂尔多斯盆地致密砂岩储层孔喉分布特征及其差异化成因

致密砂岩中广泛发育的微纳米级孔喉体系是致密砂岩储层与常规砂岩储层的本质区别，也是影响致密油藏渗流特征及开发效果的主要因素。利用铸体薄片、扫描电镜、恒速压汞等方法，对鄂尔多斯盆地姬塬地区长6段、长7段储层的孔喉类型及分布特征进行了分析对比，并对其差异性成因进行了探讨。结果表明：长6段储层孔隙类型以剩余粒间孔为主，喉道多为压实成因，孔隙较喉道发育。长7段储层孔隙类型以长石溶孔为主，喉道多为溶蚀成因，喉道较孔隙发育。2个层位孔隙半径分布范围及平均值相近，长6段储层喉道半径分布范围及平均值明显大于长7段储层，其物性好于长7段储层。长6段储层为三角洲沉积，埋深较浅，较高的绿泥石膜含量和较低的压实强度使其较好地保持了原始沉积孔隙空间，而溶蚀作用又进一步扩大了孔隙空间。长7段储层为湖泊沉积，埋深较大，压实作用和胶结作用强烈，原始沉积孔隙空间被大量挤压，后期虽发生强烈的溶蚀作用，但溶蚀成因喉道连通性和渗流能力明显低于压实成因喉道，溶蚀作用虽能增大储集空间，但无法显著提高渗流能力。因此，连续沉积的长6段、长7段储层渗透率存在显著差异。

Pore size distribution of tight sandstone reservoir and their differential origin in Ordos Basin

The micro-nano pore throat system widely developed in tight sandstone is the essential difference between tight sandstone reservoir and conventional sandstone reservoir, and is also the main factor affecting the seepage characteristics and development effect of tight sandstone reservoir. This thesis analyzed the pore-throat types and distributions of Chang6 and Chang7 reservoirs in Jiyuan area of Ordos Basin, and discussed the original causes of them by cast section, SEM, and constant-rate mercury injection. The results showed that: The pore type of Chang6 reservoir is predominantly residual intergranular pores, and the throats are mostly compacted, the pore of Chang6 is more developed than throat. The pore type of Chang7 reservoir is mainly feldspar solution pores, and the throat is mostly dissolution, the throat of Chang7 is more developed than pore. The pore radius distribution range and average value of Chang6 reservoir are similar to those of Chang7 reservoir. The distribution range and average value of throat radius of Chang6 reservoir are obviously larger than that of Chang7 reservoir, and the physical property of Chang6 reservoir is better than that of Chang7 reservoir. The Chang6 reservoir is located in delta sediments with shallow burial depth. The high chlorite membrane content and low compaction strength of Chang6 reservoir make it better to maintain the original sedimentary pore space, and the dissolution further enlarges the pore space. Chang7 reservoir is located in lacustrine sediments with a large burial depth. The compaction and cementation of Chang7 reservoir are strong, and the original sedimentary pore space is massively compressed. Although dissolution occurs in the later stage strongly, the connectivity and seepage capacity of the throat of dissolution origin are lower than those of compaction origin. Dissolution can increase the reservoir space, but it cannot significantly improve the seepage capacity. Therefore, there is a significant difference in permeability of the two successive layers.