Continuous sand production and foamy oil behavior are both believed to be key factors for the enhanced non-thermal fluid production in unconsolidated heavy oil reservoirs in Canada (Alberta and Saskatchewan). The same mechanisms are likely to be active in similar heavy oil strata in Venezuela (Faja del Orinoco), Oman, China (Bohai Bay), and elsewhere. Field experience indicates that fundamental understanding of sand production mechanisms, reservoir fabric alteration, foamy oil behavior, pressure gradient changes, and stress changes are key to successful operations involving massive continuous sanding. Inter-relating these factors requires coupling of geomechanics and fluid flow processes.

An integrated approach incorporating a three-phase, three-dimensional black-oil model coupled with a geomechanics model is introduced in this article. Piping channels ("wormholes") are postulated to develop from perforations when pressure gradients exceed the residual cohesion of the sand. An elastoplastic constitutive model is used to describe the reservoir material before seepage forces liquefy and suspend the sand particles at the advancing tips of wormholes. The hemispherical wormhole tip is postulated to propagate as long as a critical tip pressure gradient is exceeded. A slurry transport model is used to describe the flow inside the wormholes. Field data from Frog Lake, Alberta are used to validate the model, and it appears that the simulation can match the field data remarkably well.

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