Flow Diagnostics for Optimal Polymer Injection Strategies

This work extends the applicability of a class of flow-diagnostic computational tools for interactive visualization and fast simulation approximations to also account for polymer mobility effects. Flow diagnostics, as used here, employ simplifications to the reservoir flow equations to enable computation of quantitative (and detailed) information about the flow behavior of full 3D reservoir models within a few seconds. Previously, we have utilized a linearized pressure equation and a corresponding set of time-of-flight (TOF) and stationary tracer equations to compute dynamic heterogeneity measures that correlate well with oil recovery for waterflooding scenarios. To also approximate the macroscopic effect of EOR injection strategies, we suggest an implicit approach for flow diagnostics in which polymer mobility effects are included approximately in the flow equation by linearizing the flux functions. Although this linearization has a pronounced smearing effect on the water and polymer fronts, we show that the heterogeneity of the total flux field is adequately represented. Subsequently we (re)solve the transport equations accurately along a 1D TOF-grid for each well-pair region. A recovery proxy is then obtained by accumulating each 1D solution weighted by a corresponding total TOF-distribution function. We apply our new approach to 2D and 3D reservoir simulation models, and observe close agreements between the suggested single-step approximations and results obtained from full simulations. Furthermore, we demonstrate that explicit versus implicit versions of the proxy can be utilized to differentiate between macroscopic and microscopic sweep improvements resulting from polymer injection. For the examples considered, we demonstrate that macroscopic sweep improvements alone correlate better with measures for heterogeneity than the combined improvements.