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The Interplay between Viscous and Gravity Forces in Two-phase Stratified Reservoir Crossflow
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, ECMOR XIV - 14th European Conference on the Mathematics of Oil Recovery, Sep 2014, Volume 2014, p.1 - 10
Abstract
In stratified reservoir models, crossflow describes how communicating layers of different petrophysical properties allow fluid to pass between them. Viscous crossflow is usually thought to be driven by pressure differentials due to permeability differences between layers, and gravitational crossflow is driven by density differences between phases. In this work, numerical simulations of basic two-dimensional models are presented to demonstrate the effect of gravity-driven crossflow.
Stratified reservoir models are very relevant today, particularly as the importance of offshore carbonate reservoirs grow, with their highly laterally homogenous and vertically cyclical beds with enormous ranges of permeability. Even in reservoirs which are not completely stratified, high-permeability streaks are common, and the crossflow between them and the adjacent low-permeability layers can be vital for maximising the recovery factor.
The results of this investigation serve to demonstrate that gravitational crossflow from high to low permeability layers may not necessarily improve a two-phase displacement sweep, when the low permeability layer is not bound by an impermeable layer beneath. This suggests that, in order to build up physically meaningful analytical models of crossflow during two-phase displacement in stratified reservoirs, a greater understanding of the relative importance of viscous and gravity forces is often required.