Microscopic Fractal-Dimension Study of Rate and Viscosity Changes on Displacement Pattern by Use of 2D Glass Micromodel

Abstract

Summary Proper planning and management of enhanced-oil-recovery field projects are not possible without close attention to the pore-level events. Various glass-micromodel studies made it possible to directly observe many trapping and bypassing phenomena that develop during displacement processes as they occur in field-scale projects. Constructing a representative glass micromodel, a set of experiments is performed to accurately study the pore-level displacement patterns and structures that develop and progress at different flow rates and viscosity ratio of the fluids. The experiments cover a wide range of capillary numbers between 10−8 to 10−4 and different viscosity ratios from 1 to 18. Different fractal dimensions are calculated to quantify the front shapes and displacement patterns that are observed on the images captured during each test. On the basis of the total saturation of injected fluid at breakthrough time, it is observed that a critical viscosity ratio can be defined greater than where the recovery factor decreases with injection rate, whereas displacement efficiency improves with flow rate lower than that critical value. It is also found that the viscous-fingering, capillary-fingering, and stable-displacement regions are consistent with the Lenormand et al. (1988) classification and they can be quantified properly with the calculated fractal dimensions.