A Fully 3-D, Multi-Phase, Poro-Elasto-Plastic Model for Sand Production

Abstract

Abstract This paper presents a coupled reservoir-geomechanics model with multi-phase fluid flow for sand production prediction in a weakly consolidated formation. Sanding criteria are based on a combination of tensile and shear failure from Mohr-Coulomb theory and strain-hardening/softening. Once the failure criteria are met, an algorithm for entrainment of the sand based on the calculation of hydrodynamic and other forces is implemented to predict sand erosion. The flow of two immiscible slightly compressible fluids coupled with geomechanics has also been modeled. This allows us to account for relative permeabilities and capillary pressure dependent cohesion and rock residual strength. The onset of sanding and the sand production rate have both been simulated for open-hole and cased-hole completions under different flow conditions. The model utilizes a dynamic mesh which removes the grid blocks of sand that have failed and meet the erosion criteria. This allows the proper boundary condition to be applied to the sand face as sand is continuously produced. Good agreement with experimental observations is obtained for both the onset of sand production and the rate of sand production when simulations are conducted for open-hole completions. The post-failure elasto-plastic properties of the sand are seen to play an important role in determining the extent of sand production and the shape of the cavity created. In addition, the effect of wellbore pressure drop rate, controlled by choke adjustment, has been studied on the sanding risk. Multi-phase fluid flow effects, including relative permeability and capillary cohesion, are also shown to significantly impact the sand production.