A new approach to DEM simulation of sand production

Abstract

This paper presents a model for the investigation of sandstone degradation and sand production mechanisms coupled with fluid flow analysis using the Discrete Element Method (DEM). The model was used to investigate the effects of in-situ stresses and flow rate on sand production.We developed a linked DEM-fluid flow model for sanding analysis. The model calculates seepage forces and applies them on solid particles in the DEM model. The model accounts for permeability and porosity changes due to sandstone deformation and sand production. The DEM model was verified against poro-elastoplastic analytical solutions. Subsequently, the model was used for sanding simulation from a block-shaped sample under different far-field stress and pressure conditions. The boundary stresses and fluid pressures were varied to study their influence on sandstone degradation and sand production.The creation of a borehole in a solid block resulted in the development of uniform or V-shape breakouts around the borehole. The failure zone around the borehole expanded after the application of fluid flow and sand grain detachments. Fluid flow was observed to influence the size and mode of failure in the breakout zone and sand production. Boundary stress dominated the sanding response at higher boundary stress conditions. However, much lower sanding occurred under higher boundary stresses but low boundary fluid pressures. High tangential stresses around the borehole caused by high confining stress resulted in strong frictional interlocking that alleviated sand production. Massive sanding was observed at lower far-field stress but higher boundary pore pressure.