Modeling surfactant/polymer (SP) flooding at the field scale remains challenging despite a significant body of experimental and numerical work over past decades uncovering the flow physics associated with this particular chemical flooding approach and its modeling. In our work, we investigate a two-parameter model (the ω(CS)-model) relating surfactant concentration directly to the miscibility factor used to modify phase residuals and shapes of the relative permeability functions in SP-flood modeling.

We find that despite its simplicity, the ω(CS)-model for miscibility factor is able to reproduce results using the prevalent capillary desaturation curve approach (CDC-model). We first study a synthetic, two-dimensional reservoir with three injectors and three producers and then apply our approach to a realistic three-dimensional field example. We use streamline simulation to model the fluid flow in the reservoir, although the miscibility factor model is not limited to streamline simulation.

The main feature of the ω(CS) model is that the miscibility factor is only a function of surfactant concentration rather than surfactant concentration and Darcy velocity as in the CDC-model. While simpler models, such as the one proposed here are not predictive for core-scale simulations, simple models are the only practical way to find near-optimal solutions under the constraint of geological uncertainty, poor data, and many wells.

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