致密砂岩储层孔-喉连通性研究——以鄂尔多斯盆地长7储层为例

An investigation into pore-throat connectivity in tight sandstone reservoir:A case of the Chang 7 Reservoir in Ordos Basin

储层的孔-喉连通性是致密砂岩储层评价过程中所用到的一个重要参数,而孔-喉连通性的研究受到致密砂岩储层复杂的纳米喉道影响,其量化手段单一、表征参数不明,是当下该研究领域中的难点.为进一步完善储层连通性的表征手段,利用纳米CT技术、核磁共振冻融技术以及三离子束刻蚀结合场发射扫描电镜-PCAS(Pores and Cracks Analysis System)技术,从定性和定量两个角度对于鄂尔多斯盆地延长组7段典型(粉砂、细砂、泥质粉砂)致密砂岩样品的连通性进行不同尺度的表征分析.实验结果表明,致密砂岩孔隙的孔径大小与其所沟通的喉道数目呈正相关;致密砂岩中连通孔隙的体积对于连通性的贡献远高于连通孔隙的数目;油浸的细砂岩样品其连通性高于油斑的粉砂岩样品.实验分析认为,多方法联用的表征方法是致密砂岩储层连通性刻画的重要手段.

The pore-throat connectivity of Reservoir is an important parameter used in the evaluation of tight sandstone reservoirs.However,the study of pore-throat connectivity is affected by the complex nanometer-scale throat of tight sandstone reservoirs.Its single quantification method and unknown characterization parameters are difficult points in this field.In order to improve the characterization of reservoir connectivity,micro-nanoCT,nuclear magnetic resonance cryoporometry and triple ion beam etching combined with field emission scanning electron microscopy-PCAS(Pores and Cracks Analysis System)were used to characterize and analyze the connectivity of typical(siltstone,fine sandstone,and muddy siltstone)sandstone samples in the 7th member of the Yanchang Formation in the Ordos Basin.Experimental results show that the pore size of tight sandstone pores is positively related to the number of throats they connect.The volume of connected pores in tight sandstone contributes much more to the connectivity than the number of connected pores.Oil immersed fine sandstone samples have higher connectivity than oil stained siltstone sample.Experimental analysis shows that the characterization method of multi method combination is an important method to characterize the connectivity of tight sandstone reservoir.