基于恒速压汞技术的特低—超低渗砂岩储层微观孔喉特征

Pore throat characteristics of extra-ultra low permeability sandstone reservoir based on constant-rate mercury penetration technique

基于恒速压汞测试结果，对鄂尔多斯盆地延长组特低、超低渗砂岩储层的微观孔喉特征进行了分析，定量表征了孔喉特征参数的变化。结果表明，特低、超低渗储层的孔隙半径分布特征相似，介于100-200μm之间，峰值基本在140μm左右；相对于特低渗储层而言，超低渗储层的喉道分布范围更窄，小于1μm的喉道含量较高，变化更为敏感，孔喉半径比分布范围较宽，喉道进汞饱和度受渗透率影响较大；特低、超低渗储层孔喉特征的差异主要体现在喉道上。总体毛细管压力曲线表现出3个变化阶段，渗透率不同，各阶段受孔隙和喉道的影响程度也不同；处于中后期的超低渗储层更应注重喉道的开发。

Based on constant-rate mercury penetration technique, micro pore throat characteristics of extra- ultra low permeability sandstone reservoir of the Yangchang Formation in the Ordos Basin were an- alyzed, and the alterations of pore throat characteristic parameters were also quantitatively characterized. Pore radiuses were similar, usually 100-200μm, and the peak values were about 140μm. Compared to those in the extra--low permeability reservoir, distribution ranges of throat in the ultra-low permeability reservoir were narrow. Throats less than 1 μm accounted for large amount, and were more sensitive to permeability. Distribution ranges of pore throat radius ratio were wide and permeability had big influence on input mercury saturation of throat in ultra--low permeability reservoir. The differences of pore throat characteristics between extra-- and ultra--low permeability sandstone reservoir mainly lay in throats. 3 variation periods were identified on overall capillary pressure curves. Each period was affected by pore or throat in different extent due to different permeability. Throats should be focused on in the ultra-low permeability reservoir during the middle and latter stages.