Modeling Wellbore Erosion Using Standard and Cut-Mesh Approaches in Material Point Method

Damage of unconsolidated sandstone in drilled hydrocarbon wells can lead to the production of sand particles resulting in erosional damage to equipment and costly repairs. This paper focuses on comparing the standard material point method (MPM) with a novel material point method (cut-mesh MPM) formulation for modeling the onset and propagation of sand production in wellbores. Utilizing isoparametric elements provides some improvements over rectilinear elements for arbitrary and complex geometries, but these elements are still prone to quadrature errors and numerical instabilities as elements become partially filled due to large deformations and the erosion process. Combining cut-mesh MPM with isoparametric elements provides an improved approach for modeling the sand production process. Accurate predictions of downhole wellbore breakout and cavity damage is critical to determine both the onset and magnitude of sand production. Both standard and cut-mesh MPM are used to model a thick-walled cylinder (TWC) collapse test of Castlegate sandstone TWC. Final geometry and cumulative sand production mass indicate that cut-mesh MPM provides increased numerical stability relative to standard MPM when modeling erosion. Although this novel MPM formulation is relatively more stable than standard MPM, both methods struggle to capture the sharp localization of the physical TWC sample. Likewise, both standard and cut-mesh MPM are unable to reproduce the magnitude of sand production mass observed in the physical TWC sample. Complexities such as particle arching, strength anisotropy, and material fracturing are not modeled by standard or cut-mesh MPM; these complexities represent some of the possibilities for why numerical outputs are unable to match observed physical samples.