Numerical modeling of seepage-induced sand production in oil and gas reservoirs

An elasto-plastic, fully coupled fluid flow and deformation finite element model is proposed for modeling both tensile and shear-induced failure around deep wellbores in oil and gas reservoirs. The problem is of significant interest to the industry as the usual filter measures undertaken (e.g., liners and gravel packs) to prevent solids production (tensile failure) are not only very expensive but also they reduce productivity due to inevitable plugging of the pores in such filters. The impetus for developing the proposed model was to provide the industry with a viable tool to predict the quantity of the produced solids and its concomitant impact on fluid productivity. The proposed model employs a modified form of the Mohr-Coulomb failure envelope along with several numerical algorithms to effectively simulate failure in a numerically accurate and stable form. The model is verified and then applied to a field problem to investigate mechanisms for cavitation-induced productivity enhancement in a multi-layered coalbed methane reservoir. (C) 2002 Elsevier Science B.V. All rights reserved.