Alkali-Polymer Flooding in an Austrian Brownfield: From Laboratory to Field-Insights

We focus on optimizing oil displacement in brownfields using alkali polymers (AP) flooding. The goal is to enhance rock-fluid and fluid-fluid interactions to improve oil recovery. The evaluation includes detailed screening of AP mixtures to ensure cost-effectiveness and maximize chemical slug efficiency, using an AP pilot project in Austria as a case study. Key aspects of the study involve assessing fluid properties to select appropriate chemical concentrations. Important parameters include the stability of produced emulsions, interfacial tension (IFT) measurements, and rheological analyses. Rock-fluid interactions were examined through core flooding experiments on both low- and high-permeability core plugs to understand fluid dynamics in heterogeneous reservoirs. A novel part of the research involved simulating the in situ aging of the AP slug, which increases its anionicity over time. Two-phase core flooding with aged chemicals provided insights into the evolution of chemical effectiveness and interactions. We found that an alkali concentration of 7500 ppm was optimal for the AP slug, particularly in its interaction with dead oil with a high total acid number (TAN), leading to emulsions with microscopic instability. Single-phase core flooding showed that the AP slug from Vendor B outperformed that from Vendor A despite mechanical stability issues. However, the additional recovery factor (RF) for polymer A-based slugs was higher in both high- and low-permeability core plugs. The findings suggest that in situ aging of the AP slug could reduce costs and enhance injection performance.