Proppant placement in complex fracture geometries: A computational fluid dynamics study

Proppant transport in activated natural fractures and induced secondary fractures has been increasingly receiving attention. However, the roughness and the non-planarity of hydraulic fractures violate the assumption of a constant flow path during the proppant transport. Therefore, we utilized a computational fluid dynamics (CFD) approach to study the pmppant transport in the complex fracture network while considering the non-planarity and the surface roughness. The fracturing fluid loaded with sands (proppant) is injected to the fracture at a synthesized field-guided pumping schedule. We used the Eulerian-Eulerian frame of the two-phase turbulent flow for modeling the transport processes of which are compared to the proppant transport experiments. The results reflect that our constructed model captures the essential transport mechanisms of the dispersed phase (proppant particles) with the help of the appropriate drag model. We also find that the surface roughness of the fracture deaccelerates the particle velocity during the early injection time, while the fracture non-planarity plays more essential role to the particle transport in the fracture than other geometrical and topographic factors. More importantly, we noticed that the propped fracture heights vary up to one fold with different secondary fracture orientations. This observation would potentially surprise the production performance diagnosis later on.