Digital image analysis of distribution of immiscible fluids in natural porous media

Abstract

This article proposes a method of digital image analysis to monitor immiscible flow in soil samples. Four different natural soil samples were studied: coarse, medium, fine, and silty sand. Paraffin oil and a sodium fluorescein solution were used as the displaced and displacing phase, respectively. Immiscible flow tests were performed in a Plexiglas cell and monitored by means of digital image analysis and direct volumetric measurement. The images were processed to obtain gray levels at different stages during the tests. Saturation of paraffin oil was then computed from the gray level and a linear regression equation was developed for each soil tested. The proposed method enabled valuable information to be obtained of the processes that take place at the face of the samples during liquid displacement and in the middle of the samples at the end of the tests. This procedure was very effective for analyzing different flow patterns, isolating areas with trapped paraffin oil, and to determining the ganglia size distribution at different stages of the immiscible flow tests. The results indicated that particle size and microstructure heterogeneities determine the flow pattern features observed during the immiscible displacement of paraffin oil by water.