Abstract
The placement of proppants in hydraulically fractured wells determines the conductivity of fractures and productivity of shale wells. In slickwater farcturing, proppants are often not transported deep into fractures. In this paper, proppant transport in foam-based fracturing fluid is visualized in a laboratory-scale fracture slot. Effect of parameters like foam quality, proppant loading, and injection rate are systematically investigated. Additionally, a CFD based model is developed to simulate the lab experiments by assuming the foam as a single-phase non-Newtonian fluid. Experiments show that dry foams (80% quality) can carry proppants between the lamellas with little vertical settling. A complex flow pattern is developed at the bottom of the slots in dry foams due to protrusion of foam fingers into proppant laden foam flow. Proppants are not carried very well in wet foams (70% quality) and form a proppant bed near the injection well. This is due to severe drainage of surfactant solution from the foam as it moves through the fracture. CFD simulation of proppant transport agrees approximately with the experimental observations for the dry foams. The simulation results do not agree with the experimental observations for the wet foams. The assumption of treating foams as a continuum non-Newtonian fluid is not valid for wet foams where drainage of surfactant solution is significant.
