The Wormholes Formation During the Cold Heavy Oil Production with Sand (CHOPS)

Cold heavy oil production with sand is a primary recovery method extensively used in the world as a profitable and simple technology. CHOPS is a single well technology that involves the deliberate initiation and sustaining of sand inflow into the wells using progressive cavity pumps to produce at oil high rates with a subsequent high-pressure drawdown around the wellbore and improvement in oil well productivity. Foamy-oil flow and wormholes formation are the main mechanisms of aggressive sand production. The wormholes are channels of high-porosity and high-permeability, which are generated during the early stage of massive sanding. These channels are cavities or volumes full of slurry, in which there is no grain-to-grain contact. An alternative methodology is proposed to model the initiation and propagation of wormholes incorporating failure criteria, and porosity and permeability changes during sanding under critical production conditions. The wormholes initiate due to in-situ stresses, failure criteria, pressure gradient, and erosion, which define four zones around the well: liquefied zone, yielded zone, transition zone and intact zone, each one with different mechanical and petrophysical properties, which are changing during the oil and sand production. A single well model that couples a three-phase fluid flow model and an elastoplastic model is the tool to apply the wormhole methodology. The general characteristics of the coupled model are described in detail, a flowchart is presented to display the methodology and the delineation of the four different zones. A preliminary case is run to demonstrate the wormhole formation and its effect on the well productivity with suitable results in terms of increment in porosity and permeability, and the advance of the wormhole.