低渗透砂岩储层微观孔隙结构特征——以鄂尔多斯盆地志靖—安塞地区延长组长9油层组为例

Characteristics of microscopic pore structure in the low permeability sandstone reservoir: A case study of Chang 9 of Yanchang Formation in Zhijing-Ansai area of Ordos Basin

通过物性分析、铸体薄片、扫描电镜技术、常规高压压汞技术、恒速压汞技术等,对选自鄂尔多斯盆地志靖—安塞地区长9段低渗透砂岩储层样品进行测试分析,获取储层孔隙、喉道的形态、类型、连通程度等信息,确定孔喉大小、分选情况和连通性的定量参数。研究表明,研究层位孔隙类型主要为残余粒间孔、溶孔、微孔。将孔隙组合特征分为4种类型,储层孔隙结构具多样性。样品孔喉结构整体上具有大孔隙、细喉道的特点,微细喉道的发育是造成物性渗透率超低的主要原因。储层孔隙结构的多样性及不均一性是导致储层非均质性的主要原因。

In this paper, the authors investigated characteristics of microscopic pore structure in low permeability sandstone reservoir for providing the basis for further exploration and development. By means of physical property analysis, SEM, casting slice, high pres- sure Hg injection, and rate-controlled Hg penetration, the authors selected low permeability sandstone samples from Chang 9 of Yan- chang Formation in Zhijing-Ansai area of Ordos Basin and made analysis. The information of reservoir pores, types and the morphol- ogy of throat and its degree of connectivity was obtained, and the quantity factors about the size of pore and throat, sorting and con- nectivity were determined. The results show that the pores mainly consist of residual intergranular pores, solution pores and micro- pores. The pore combination is divided into four types which reflect the diversity of pore structure. Pore structure of the samples is characterized b larKe pore and fine throat. The development of fine throat is the main reason responsible for ultra-low permeability.The diversity and heterogeneity of the reservoir pore structure is the main cause of the reservoir heterogeneity.