特低-超低渗透砂岩储层微观孔喉特征与物性差异

The Relationship between Micro-Pore Throat Characteristics and Physical Property Difference in an Extra-Ultra Low Permeability Sandstone Reservoir

为揭示特低-超低渗透砂岩储层微观孔隙结构与物性差异的关系,利用物性分析、铸体薄片、电镜扫描和高压压汞技术对鄂尔多斯盆地延长组3个典型的特低-超低渗透砂岩储层岩芯样品进行了实验测试。研究结果表明,特低-超低渗透砂岩储层喉道类型多样;但整体细小,对渗透率起主要贡献的较大喉道含量小是其物性较差的主要原因,同时微裂缝的发育也加剧了物性差异。统计对比发现,孔喉的分选系数在2.0～3.0,变异系数在0.15～0.3,对渗透率贡献相对较大。可见,储层物性是多种因素共同影响的综合反映,不同类型孔隙、喉道组成的储集空间,渗透率存在较大差异,物性差异正是孔喉特征差异的一种具体表现。

In order to study the relationship between micro-pore throat characteristics and physical property difference,drill core samples of extra-ultra low permeability sandstone from a reservoir in the Yanchang group of the Ordos Basin were selected for physical property analysis,cast section,SEM and mercury penetration techniques.The results indicate that throat type in an extra-ultra low permeability sandstone reservoir is versatile and minute.The content of major throat which makes a dominant contribution to permeability is low,which is the main reason for poor physical property.Meanwhile,micro-cracks aggravate the difference in physical property.The distribution and variation coefficients range from 2.0 to 3.0 and 0.15 to 0.3 respectively,providing a major contribution to the permeability of sandstone.Physical property is the combined result of the mutual effect of multiple factors.Permeability presents large deviation when the reservoir space is composed of different pore throat types.