采用CT技术研究岩心剩余油微观赋存状态

油层孔隙中剩余油的微观赋存状态是指导剩余油挖潜的重要依据。借助CT微观驱替实验系统，获得了水驱不同驱替时刻岩心模型的CT扫描图像，利用图像处理技术实现了岩心模型图像信息向三维数据体的转化。在此基础上提取剩余油的信息，提出了剩余油块数、平均体积、接触面积比、形状因子等指标对孔隙尺度下剩余油的微观赋存量、赋存位置及赋存形态进行定量表征。实验结果表明：随着驱替的进行，岩心模型中剩余油块数增多、平均体积减小，尺寸小于20倍平均孔隙体积的剩余油在数量上占绝对优势，该类剩余油所占的体积比例逐渐增大；剩余油逐渐从岩石表面剥落下来，水驱至残余油时刻水湿岩心中仍有约1/3的剩余油与岩石表面接触；剩余油形态由网络状向其他类型转化，驱替至残余油时刻以网络状和多孔状为主，结构相对复杂的网络状及多孔状剩余油是注水开发后期的主要挖潜对象。

Characterization of residual oil microdistribution at pore scale using computerized tomography

The microdistribution of residual oil in reservoir pore is an important basis for remaining oil potential tapping. With the aid of computerized tomography(CT) scanning and displacement experimental system, CT images at different displacement moments were acquired, these images were then transformed to three-dimensional data volume by image processing technology. On this basis, information of residual oil was extracted and such characteristic parameters as number, average volume, contact area ratio and shape factor were defined to characterize the microdistribution of residual oil at pore scale. Experimental results showed that: the number of residual oil increased and average volume decreased with the increase of injected water volume; oil blobs smaller than 20 times average pore volume constitute the overwhelming majority of residual oil in quantity and their total volume ratio increased; residual oil were washed out from the rock surface gradually and nearly one third oil blobs had contact with the rock surface in water wet core; shapes of oil blobs changed from meshwork to other forms. Meshwork and multiple pore forms were in the majority at the end of the displacement so that they were the principal object of potential tapping during later stage of water-injection recovery.