Nanofluid Precoating: An Effective Method To Reduce Fines Migration in Radial Systems Saturated With Two Mobile Immiscible Fluids

Abstract

Summary Prediction of how nanofluid applications can potentially control fines migration in porous media saturated with two immiscible fluids requires a mechanistic modeling approach. We develop analytic solutions to evaluate the efficiency of nanofluid utilization to reduce fines migration in systems saturated with two immiscible fluids. In this study, fines migration in the radial-flow system saturated with two immiscible fluids (oil and water) is considered; two capture mechanisms of fine particles—fines attachment and straining—are incorporated into the modeling work. The analytic solution is derived by implementing the splitting method and stream-function transformation to convert a 2 × 2 (nonhomogeneous) system of equations into an equation with a fine-particle component (nanoparticle effects) and a lifting equation in which only water saturation appears. Through quantitative comparison of suspended fines and water-saturation-profile plots, the accuracy of the analytic solution is verified with finite-difference numerical solutions. Saturation c-shock and saturation s-shock appear in the analytical solutions. The fines migration and consequent phenomena (fines attachment, fines straining, and fines suspension) decelerate the breakthrough of the injected fluids (better sweep efficiency) and increase the corresponding front saturation of the injected fluid near the wellbore—i.e., larger relative permeability (better injectivity). The results suggest that fines attachment onto the grain surface and well injectivity are enhanced after nanofluid pretreatment; moreover, the smallest radius to be pretreated by nanofluid is approximated to maintain its benefits. In practice, our analytic approach provides a valuable mathematical structure to evaluate how nanoparticle usage can enhance performance of water-based enhanced-oil-recovery (EOR) techniques in reservoirs with a fines-migration issue.