Performance of Polymer Flooding in Anisotropic Reservoirs with Discontinuous Streaks of Shale

Abstract

Many oil reservoirs contain discontinuous shale streaks, which may affect the flow behavior as well as oil recovery efficiency. To investigate and compare the performances of polymer flood processes in anisotropic shaly reservoirs, an extensive numerical simulation was performed for polymer flood followed by waterflood. A series of polymer and water injection simulations have been carried out at various conditions in the length, direction, and spacing of shale streaks and level of reservoir anisotropy. Reservoir performances were compared in terms of cumulative recovery and water-oil ratio at the production well and injectivity at the injection well. Results from the study have demonstrated that oil recovery can be significantly affected by shale streaks with increased length and shorter space. It was observed that the shale streaks cause bypassing of displacing fluids due to disruption of main flow path and, consequently, lower injectivity. Increasing shale content causes the degree of fingering to be increased significantly during polymer flooding. The effects of heterogeneity introduced by streaks of shale were maximized when the direction of displacing fluid flow was perpendicular to the direction of shale streaks and parallel to higher permeability in the anisotropic reservoir models. Results of this work can be helpful for successful design and accurate prediction of EOR processes based on shale distribution in anisotropic reservoirs.