Abstract
Cold Heavy Oil Production with Sand (CHOPS) is a well-known primary heavy oil recovery method. In CHOPS, a key mechanism of production is the formation of wormholes. Wormholes are believed to be nearly cylindrical zones of high permeability that originate from production wells when sand is produced along with the oil. A multi-scale modelling approach based on the multiphase material point method (MMPM) has been applied to the problem of developing a general predictive capability for CHOPS and wormhole growth. The MMPM is a Lagrangian-Eulerian methodology which permits simulation of multiphase flow problems with fluid-structure interaction in which there is substantial material deformation, damage and failure. MMPM is applied to the problem of simulating the growth of a wormhole in unconsolidated sand with live oil including the effect of foamy oil and sand failure. The simulation results show general features such as asymmetry and slugging. Comparison with experimental data for wormhole length with time was favourable. Up-scaling of the method is required to make predictions on the well to field scale. For this purpose, an up-scaled pressure-field-driven scheme has been developed to predict wormhole network structure. It is hypothesized that a pressure-field-based approached is adequate for a macroscopic simulation with resolution above the length scale of the wormhole tips at which the tensor nature of the failure mechanics are more important. The model includes a generalized sand failure criterion that couples with a non-linear pressure equation and foamy oil and sand flow equations. The model resolves separate wormhole regions emerging from the CHOPS pilot well. Robust history matching of commercial pilot production data is provided as partial model validation.
