Particle mobilization in porous media: Temperature effects on competing electrostatic and drag forces

The fluid flow in natural reservoirs mobilizes fine particles. Subsequent migration and straining of the mobilized particles in rocks greatly reduce reservoir permeability and well productivity. This chain of events typically occurs over the temperature ranges of 20-40 degrees C for aquifers and 120-300 degrees C for geothermal reservoirs. However, the present study might be the first to present a quantitative analysis of temperature effects on the forces exerted on particles and of the resultant fines migration. Based on torque balance between electrostatic and drag forces acting on attached fine particles, we derived a model for the maximum retention concentration and used it to characterize the detachment of multisized particles from rock surfaces. Results showed that electrostatic force is far more affected than water viscosity by temperature variation. An analytical model for flow toward wellbore that is subject to fines migration was derived. The experiment-based predictive modeling of the well impedance for a field case showed high agreement with field historical data (coefficient of determination R-2=0.99). It was found that the geothermal reservoirs are more susceptible to fine particle migration than are conventional oilfields and aquifers.