Speaker
Description
Non-Newtonian fluids play an important role in enhanced oil recovery, drilling engineering, and fracture stimulation of wells. Yet, in much of the related numerical modelling, a Newtonian rheology is assumed, ignoring the impact of fluid viscosity variation with flow rate on engineering outcomes.
Here, we examine the influence of a non-Newtonian rheology on flow structures and distributions in natural fracture networks. The Navier-Stokes equation is solved numerically, and polymer solution rheology, including yield stress and shear-thinning behaviour, is modelled using the Herschel-Bulkley-Papanastasiou approach. Comparison with Newtonian fluid reference runs, reveals that rheology alters fracture flow significantly. For a range of network fluid throughputs, viscosity variations control the flow distribution, reinforcing flow along straight, far-field pressure-gradient aligned fractures. At low throughputs, a pronounced yield stress effect creates unyielded regions, blocking fracture-side branches or attenuating flow into them. Solid-like regions, including stagnant and flowing ones, can account for ~65% of the fracture network volume, seriously reducing overall flow. At elevated throughputs, shear-thinning (modelled as reversible) reduces apparent fluid viscosity, enhancing fluid inertia effects. This encourages flow along low-resistance fractures and creates swirling secondary flows at intersections. For the same throughput, inertial losses enhancing the total pressure drop across the tens-of-metre-sized network are up to ~30 times larger than for the non-Newtonian fluid. Observed multimodal velocity distributions and nonlinear pressure drop-flow rate relations underscore that fluid rheology is critical for fracture network flow.
| Country | Australia |
|---|---|
| Acceptance of the Terms & Conditions | Click here to agree |
