基于数字岩心的致密砂岩微观孔喉结构定量表征

Quantitative characterization of pore throat microstructure of tight sandstone based on digital core technology

微观孔喉结构是决定致密砂岩储层物性的内在因素,定量描述微观孔喉结构特征可以为致密砂岩储层质量表征提供依据。但致密砂岩储层微纳米孔喉发育,微观非均质性强,常规实验手段难以准确地确定孔喉特征参数。在高精度数字岩心图像的基础上(以SEM-Maps扫描图像为例,分辨率为10 nm),建立致密砂岩多孔介质模型,研究形成了自适应孔喉识别与提取方法、基于图像形态学算法的孔喉分割方法、孔喉结构特征参数计算方法,实现了基于扫描图像的致密砂岩微观孔喉结构定量表征。选取3块红河油田长8储层典型井致密砂岩岩样,定量计算孔喉特征参数,分析不同岩样的孔喉结构差异,结果表明:岩样的宏观物性与微观孔喉结构特征密切相关,孔喉半径越大、数量越多、配位数越高、连通性越好,岩样的渗透率等宏观物性也越好。

The pore throat microstructure is an internal factor that determines the physical properties of tight sandstone res⁃ervoir.Therefore,describing the characteristics of pore throat microstructure in a quantitative manner can provide a basis for studying on the quality characterization of tight sandstone reservoir.However,the micro-nano pore throats in tight sand⁃stone reservoir are developed with strong micro heterogeneity,so it is difficult to accurately determine the characteristic pa⁃rameters of pore throats by conventional experimental methods.In this paper,on the basis of high-precision digital core im⁃age(taking the SEM-Maps scanning image with resolution 10 nm as an example),a porous media model of tight sandstone is constructed.Furthermore,the paper has developed methods,including adaptive recognition and extraction of pore throats,the segmentation of pore throats based on image morphological algorithm,and the calculation of characteristic pa⁃rameters of pore throat structure.In this way,the quantitative characterization of pore throat microstructure of tight sand⁃stone based on the scanning image is realized.This paper selects three typical rock samples of tight sandstone from Chang8 reservoir in Honghe Oilfield in an attempt to calculate the characteristic parameters of pore throats quantitatively and to an⁃alyze the structural differences of pore throats.The results show that the physical properties of rock samples are closely re⁃lated to the characteristics of pore throat microstructure and the more pore throat,the larger pore throat radius,the higher coordination number and the better connectivity of pore throat all make the permeability and other physical properties of rock samples better.