孔隙结构对低渗-特低渗砂岩储层渗流特征的影响段储层为例——以鄂尔多斯盆地东部上古生界盒8段储层为例

通过铸体薄片显微镜下观察、孔喉图像、毛细管压力、恒速压汞、气水相对渗透率、核磁共振等多种分析实验手段,研究了鄂尔多斯盆地东部上古生界盒8段低孔、低渗-特低渗砂岩储层的微观孔隙结构和渗流特征,探讨了孔隙结构对储层渗流特征的影响。结果表明,孔隙结构特征是影响低孔、低渗-特低渗砂岩储集性能与渗流特征的主要因素。而砂岩的孔隙结构特征主要受砂岩原生矿物组合与成岩演化过程及其产物的控制,盒8段各砂岩类型由于其矿物成分不同导致孔隙结构的差异,也是各砂岩类型储集性能与渗流能力存在差别的直接原因。在孔隙结构参数中,喉道的大小、有效孔隙与喉道的体积及其连通性是决定储层储集与渗流能力的关键。大孔喉对储层渗流能力的贡献更大,中-小孔喉则对储集能力的贡献相对较高。微裂缝是除孔隙结构以外影响砂岩储集性能与渗流特征的重要因素。

Impact of pore structure on low to very low permeability sandstone reservoir percolation characteristics:A case study from the He 8 reservoir of the Upper Paleozoic in the eastern Ordos Basin

Pore structure and percolation characteristics of the He 8 sandstone reservoir with low porosity and low to very low permeability,Middle Permian,Upper Paleozoic from the eastern Ordos Basin is studied.Impact of pore structure on sandstone reservoir percolation characteristics is discussed in this paper,based upon observation of vacuum impregnate with epoxy resin thin sections under microscope,pore and pore throat image and capillary pressure analysis,constant speed mercury injection and two facies of gas-water permeability experiments,nuclear-magnetic resonance measurement.Research result shows that the main factor affect percolation characteristics and sandstone reservoir quality with low porosity and low to very low permeability is the pore structure features.While pore characteristics were attributed to primary mineral assemblages and diagenetic evolution processes,types of products during which were produced and their distribution in the He 8 sandstones.Among the pore structure parameters,pore throat size,valid pores,volume of pores and throats,and connectivity between pores and throats are the key parameters impacting reservoir quality and percolation capacity.Research also indicates that the larger pore throat is,the more contribution is to the reservoir percolation, Whereas,middle to small sized pore throat is relatively contributes more to reservoir quality.In addition to pore structure,the micro fractures and fissures in sandstones is one of the important factors effecting reservoir quality and percolation characteristics.