Simulation & Economics

Reservoir simulation for polymer flooding. Predicting polymer injectivity in chemical Enhanced Oil Recovery (EOR) processes remains a significant challenge due to a variety of complex factors that are not fully captured by current commercial simulators. One of the primary difficulties arises from the non-Newtonian behavior of polymer solutions, which exhibit shear-thinning and shear-thickening properties. These properties, influenced by varying shear rates in the reservoir, make it difficult to predict the in-situ viscosity of the injected polymers, as the polymer’s flow characteristics can change depending on pressure and flow regimes. This rheological complexity is further exacerbated by reservoir heterogeneity and the presence of fractures or microfractures, which are common in many field projects.

Fractures can improve injectivity by creating more efficient flow paths, but their presence complicates the modeling of fluid behavior, especially as fractures can evolve over time.

Current reservoir simulation models often rely on Darcy flow assumptions, which are insufficient for capturing the complexities of polymer flooding. Grid resolution, upscaling issues, and numerical dispersion further contribute to inaccuracies in predicting polymer distribution and propagation within the reservoir. In addition to these simulation challenges, near-wellbore conditions also play a critical role in injectivity, with phenomena such as polymer mechanical degradation and drag reduction influencing injection rates. Simulators often require adjustments, such as modifying skin factors, to align with actual field data, but these modifications can be ad hoc and imprecise.

Furthermore, understanding how polymers behave inside the reservoir is crucial, especially in predicting polymer breakthrough at production wells. The polymer’s interaction with various reservoir zones and its impact on breakthrough times can significantly influence the overall efficiency of the EOR process. Ultimately, while progress has been made, current commercial simulators struggle to accurately predict polymer injectivity due to the dynamic and complex nature of polymer behavior in reservoirs, particularly in fractured and heterogeneous environments. This highlights the need for further development of simulation models that can better account for these factors and improve the accuracy of predictions in polymer injection projects.

We discuss reservoir simulation with Randy Seright in this Excel Or Routine Podcast.

Another episode discussing injectivity can be accessed here.