CHOPS refers to Cold Heavy Oil Production with Sand in Western Canada, with heavy oil and sand produced together. Being different from conventional primary recovery, wormhole propagation and foamy oil flow are observed to make CHOPS achieve considerable production. Differences between the conventional primary depletion and cold heavy oil production are discussed in terms of their drainage mechanisms, model formulation and modeling approaches.
The goal of this study is to investigate the modeling techniques on wormhole propagation and foamy oil flow as well as their effects in simulation. This study demonstrates two kinds of wormhole modeling approaches: Modeling wormholes as high permeability channels resulting from the experimental observations in which new variables are set up to model the enhanced permeability channels and modeling wormholes as well segments resulting from the extension of wormholes that build more flow paths like wells. Also, a reaction - based pseudo bubble point model is applied in the modeling of foamy oil flow. The heavy oil solution gas drive is divided into several stages in order to capture the transfers between various gas partitions.
The above different modeling approaches are implemented into a General Purpose Research Simulator. Numerical studies are conducted for pressure profiles, sand production characteristics in wormhole propagation, Gas-Oil Ratios (GOR) and Recovery Factors (RF) for foamy oil flow. The simulation results show the rationality of the proposed wormhole modeling approaches and indicate that pressure decline and a permeability increase rate are two main factors influencing CHOPS performance.