Mobilization of kaolinite fines in porous media

Abstract

Fines mobilization in porous media can lead to drastic changes in the permeability of oil reservoirs. The understanding of the mechanism of the release of fines from pore network will provide the information necessary to minimize formation damage during oil production. Thus, the main objective of the present work was to analyze the forces acting on fine particles near a representative sand grain. This was done by evaluating the hydrodynamic and colloidal forces between fines and sand grain surfaces. The comparison between them provided the criteria for determining the critical conditions for mobilization of fines. The analysis showed that for kaolinite particles, mobilization was dependent on the chemistry of the aqueous fluids present or injected into an argillaceous porous medium. The analysis was subsequently tested by comparing the predicted and the experimentally reported critical electrolyte concentration at which permeability reduction in oil reservoirs occurs due to fines mobilization. Predictions were in fairly good agreement with experimentally reported data, indicating that permeability reduction in oil reservoirs can be minimized by controlling the chemistry of the injected fluids. Direct microscopic observations using a packed microcell invaded by clay suspension were carried out in order to verify the type of interactions between kaolinite particles and sand grain surfaces. Most of the observations were in good agreement with the DLVO theory.