低渗透砂岩储层孔隙结构对储层质量的影响——以鄂尔多斯盆地姬塬地区长8油层组为例

Influence of pore structure on reservoir quality of low permeability sandstone reservoir: A case study from Chang 8 oil reservoir set in Jiyuan area, Ordos Basin

应用常规压汞、铸体薄片、扫描电镜和岩石薄片等资料,结合恒速压汞实验,综合研究了鄂尔多斯盆地姬塬地区长8低渗透砂岩储层微观孔隙结构特征及其对储层质量的影响。结果表明,长8储层孔隙类型多样,孔隙结构可划分为4种类型:Ⅰ类低排驱压力-中喉型、Ⅱ类较低排驱压力-细喉型、Ⅲ类中排驱压力-微细喉型和Ⅳ类高排驱压力-微喉型。储层物性与平均孔喉半径、中值孔喉半径、分选系数及最大进汞饱和度均具有正相关性,与结构系数均具有负相关性,而与均值系数、歪度及退汞效率均无明显相关性。恒速压汞测试进一步表明,储层物性与孔隙参数相关性不明显,储层质量主要受喉道的控制。在低渗透储层开发过程中应注重对喉道的有效保护,进而取得更好的开发效果。

Based on conventional constant-pressure mercury injection, cast image, scanning electron microscopy and slice observation, combined with constant-speed mercury injection, this paper studied the microscopic pore structure and its influence on reservoir quality of Chang 8 low permeability sandstone reservoirs in Jiyuan area. The result shows that Chang 8 reservoirs developed various pore types and the pore structure can be divided into four categories. The average pore-throat radius, median pore-throat radius, sorting coefficient and maximum mercury saturation have a positive correlation with reservoir properties, have a negative correlation with structure coefficient, and have little correlation with average coefficient, skewness and mercury withdrawal efficiency. Constant-speed mercury injection test further shows that physical properties of Chang 8 low permeability reservoir have little correlation with pore parameters, and reservoir quality are mainly controlled by throat. In the process of low permeability reservoir development, we should protect the throat effectively to achieve better development effect.