Well Injectivity and Productivity Under Fines Migration: Analytical Modelling

Abstract Formation damage due to fines migration is characterized by skin factor. Colloidal or nanoparticles are detached from the surface of rocks by water flow and are captured/strained by the matrix. Strained particles clog pore throats resulting in permeability decline, thus increasing impedance; proportional to wellbore skin. Analytical models for injectivity and productivity decline under the migration of polydisperse fines, by velocity alone are unavailable. The gap in formulae for impedance growth that accounts for non-uniformity of migrating colloids (distributions of particle/pore sizes and shapes, zeta potentials for rocks and particles, and mineral composition) is closed by the two analytical models derived in this paper. Exact solutions for radial 1D inflow and outflow problems under polydisperse fines migration are obtained. The effects of formation damage parameters, and particle property distributions on formation damage extent, during both injection and production are investigated. Results indicate that stabilized impedance in production wells is more sensitive to changes in key formation damage parameters; the drift delay factor has no impact and only affects the stabilization rate. The initial concentration of population one does not significantly affect the breakthrough profile for production wells but does for injectors. In general, it can be concluded that stabilized impedance in production wells is higher than that for injection wells. Matching of the analytical model to production data from the Chad Doba basin was successful, demonstrating the models’ applicability in field cases.