微纳米孔隙空间三维表征与连通性定量分析

Three dimensional characterization and quantitative connectivity analysis of micro/nano pore space

利用FIB-SEM(聚焦电子-离子双束扫描电镜)三维成像表征技术和数字岩石技术,开展非常规储集层孔隙连通性评价研究。利用FIB-SEM三维成像功能得到高分辨率的储集层数字图像,通过形状矫正、亮度矫正、景深矫正和物相区分等数字岩石技术将数字图像转换为可供进一步分析的孔隙结构数字模型,基于此模型提出一种孔隙连通性评价方法,将孔隙连通域进行分级:死连通域为孤立孔隙,1级连通域最差,3级连通域最好;在此基础上统计各级连通率并进行连通域提取,对特定连通域进行数量、体积和形状等参数的统计分析,从而实现孔隙空间的量化表征。实例应用表明纳米合成材料、页岩、致密碳酸盐岩连通率具有显著差异(分别为96%、22%和82%),连通域数量、体积和形状分布规律亦不同;通过上述量化指标(各级连通率、连通域数量、体积和形状参数),有效区分了此3类典型材料和储集层的孔隙空间特征,证实了该方法的有效性。

Evaluation is performed on pore connectivity of unconventional reservoirs using 3-D FIB-SEM imaging characterization and digital rock techniques. 3-D images are first obtained by FIB-SEM device and then transformed into digital pore structure model through shape correction, brightness correction, depth-of-field correction and phase distinguishing. Based on this model, a new connectivity evaluation method for micro/nano pores in unconventional reservoirs is proposed. This method differentiates dead and live pore space, grades live connected domains（1-grade is the worst and 3-grade is the best） and calculates the connectivity rates of all grades. Selected connected domains can be quantitatively characterized through statistical analysis of connected domain distribution, volume and shape. The applications on nano material, shale and carbonate get distinctive connectivity rates（96%, 22% and 82%） and characteristic differences on connected domain distribution, volume and shape. Through these statistical parameters（connectivity rate, connected domain distribution, volume and shape）, the three demonstrated materials and reservoirs are quantitatively characterized and differentiated. Thus, validity of the proposed connectivity method in this paper is proved.