The Self-flattening Nature of Trailing Shocks in Augmented Waterflooding – Segregation-in-flow Reestablish Self-sharpness

Abstract

One of the challenges for reservoir simulation is numerical dispersion. For waterflooding applications the effect is controlled due to the self-sharpening nature of a Buckley-Leverett shock. In this paper, we show that for augmented waterflooding – due to the coupling of compositional dispersion with fractional flow – the trailing shock is no longer self-sharpening. Thus, the simulation of such processes suffers from even higher numerical dispersion effects compared to pure waterflooding. Rather than implementing a higher-order discretization method, we propose a simple scheme based on segregation within a grid block. Compared to current mixing schemes, it differs in that segregation not only affects fluid properties but the transport, too. The scheme is shown to reestablish self-sharpness across the trailing shock. Simulations are performed that demonstrate the effectiveness of the scheme. The simulations also illustrate the possible effects of numerical dispersion on the predictions of augmented waterflooding. Finally, we discuss the extension of this technique to compositional simulation through a coupled limited-flash/segregation-in-flow assumption. Preliminary results demonstrate the potential of the approach as a heuristic method to control numerical dispersion for the simulation of miscible and near-miscible gas injection processes.