Microfluidic Study of Polymer Permeability Reduction Mechanisms

Abstract

Abstract Polymer solutions see broad applications in hydraulic fracturing, enhanced oil recovery, conformance control, and groundwater remediation. However, due to the high viscosity of polymer solutions, flows after polymer injection are often subjected to significant pressure build-up, the mechanism of which is not well studied, especially on the effect of distribution of fluids in the pores. In this study, we used microfluidics micromodels to visualize the distribution of fluids in porous media. NOA81 micromodels with close-to-real-rock pore dimensions were fabricated and used for simulating flooding experiments. Relative permeability was measured at steady-state flow rates and injection pressures. Then, fluid distribution was analyzed using microscopy image analysis. We observed that the distribution of fluids in a porous medium has a direct impact on the pressure drop. The relative permeability of water and oil after polymer flow was disproportionally low, which is consistent with core flooding experiments. The increase in the pressure drop due to polymer trapping can be correlated to occupancy, orientation and alignment of pore channels. A mathematical model was developed to describe the correlation between pore-scale fluid distributions and the end-point relative permeability; it can be used for understanding and enhancing oil/water flows during/after polymer injections.