Polymer-Flood Modeling Using Streamlines

摘要

The successful design of a polymer flood relies on the ability to properly model the in-situ distribution of polymer concentration while accounting for its effects on fluid properties such as increasing water viscosity as a function of polymer concentration and loss of polymer caused by adsorption. Despite advances in numerical techniques and computer hardware, the numerical modeling of polymer floods using Eulerian-based approaches such as finite difference (FD) remains a challenge: Coarse grids tend to excessively smear concentration fronts, masking the true impact of polymers; yet introducing finer grids inevitably leads to excessive run times, making the use of modern reservoir-engineering workflows unrealistic. This problem was already outlined by Lake et al. (1981). We revisit the same problem 30 years later in the context of modern streamline (SL) simulation techniques.rnWe present the extension of modern SL simulation to field-scale polymer flooding, which represents a step change from the hybrid, 2D steady-state models used in the 1970s. We apply well-established physical models for polymer flooding to capture the displacement efficiency in ID, and couple it with a 3D SL simulator to capture the interpattern sweep efficiency caused by well rates, reservoir architecture, and reservoir heterogeneity. Because modern 3D SL simulators account for changing well rates, nonuniform initial conditions, and gravity, adding polymer functionality means that real-field polymer floods can be modeled efficiently using SLs so as to be useful in modern reservoir-engineering workflows that center on assessing uncertainty and risk associated with design parameters and geological scenarios.rnIn this paper, we proceed to outline the basic architecture of a SL simulator with a polymer option. The physics of polymer flooding is the same as that being used in established FD codes. We discuss advantages and disadvantages of the formulation and present numerical experiments in 1D, 2D, and 3D to illustrate our results.