Modeling Sand Production and Wormhole Growth using Pressure and Stress Continuity at Wormhole Tip

Wajih Naeem

Cold Heavy Oil Production with Sand (CHOPS) is a primary recovery mechanism in which sand is aggressively produced with oil to enhance the oil production rate, which is significantly greater than the oil rate expected by conventional Darcy’s law. Field and experimental investigations have shown that wormholes are generated as a result of aggressive sand production in CHOPS; these wormholes provide regions of enhanced permeability and porosity to the oil flow in the reservoir. In order to understand wormhole mechanics in CHOPS, two models are developed:
1. Modeling Sand Production due to tensile failure in reservoir caused by hydrodynamic Force: tensile failure of sand is a major cause of sand production in regions away from wellbore in CHOPS. In this model tensile sand failure is simulated using drag forces acting on the sand grains caused by heavy oil flow. Microscopic drag forces acting upon sand grains are determined to estimate the sand production in CHOPS caused by tensile failure.
2. Modeling Sand Production and Wormhole Growth using pressure and radial stress continuity at wormhole tip: this model presents an approach to tracking wormhole propagation using fluid pressure and stress continuity at interface between the wormhole network and intact region. Pressure and stress equations are developed inside the wormhole network and in the intack region, and continuity at the interface between these two regions is then assumed to track the wormhole growth in the reservoir. Numerical simulations of the model are performed using typical reservoir parameters for CHOPS and the results show good accuracy in simulating cold produced reservoir behavior.