Migration of formation fines into a gravel pack frequently causes a severe reduction of gravel pack permeability and consequently affects well’s productivity. In sand-producing formations, a cased hole gravel-pack is usually the preferred completion method. The unsteady state migration of formation fines into gravel-filled perforations during single phase flow has not been included in previous models. In this study, a new approach is proposed to predict gravel-pack permeability reduction due to fine migration considering non-Darcy flow and particle transport in gravel filled perforation. The model focuses on mobilisation of formation fines from the pore wall and simultaneous deposition on to gravel filled perforations. The non-linear differential momentum and continuity equations have been discretised by means of an implicit finite difference scheme. Results can be used to predict any impairment to gravel-pack permeability and to evaluate the skin factor outside the casing. The selective perforating effect on a well’s performance is also studied and gravel-pack permeability reduction is determined for a given perforation design. The results indicate that perforation parameters including perforation density, perforation diameter and perforation phase angle are the most dominant parameters in controlling the long-term performance of gravel filled perforated wells.
Keywords: perforation, permeability impairment, non-Darcy flow, skin factor, gravel-pack