Optimizing Polymer Flooding in Multilayered Reservoirs: Insights from Connectivity, Composition, and Field Performance

Summary This study evaluates the performance of polymer flooding in a complex, multilayered reservoir, where isolated layers exhibit varying degrees of connectivity. Throughout the polymer flooding pilot, produced fluid samples were collected at different stages and analyzed to determine polymer concentration and chemical composition. Aging tests were also conducted under reservoir conditions to track changes in the polymer’s chemical composition over time, offering insights into how the polymer behaves in situ. Initially, the pilot area contributed around 1.5% to the total field response. After polymer injection, this contribution increased to approximately 12%, with oil production rising between 4 to 10 times, depending on the producers. Water cut dropped from an average of 97% to 80%, and in some areas, it decreased as much as 36%. However, the oil response across the pilot area was uneven, driven by differing levels of connectivity between the reservoir layers. In some sections, a rapid oil response was observed, accompanied by early polymer breakthrough at high concentrations and limited hydrolysis, quickly followed by a decline in oil rate. This suggests preferential flow through a specific layer, allowing for fast but short-lived oil recovery, leaving other layers poorly swept. Conversely, in other sections, oil production increased more gradually, with delayed polymer breakthrough at lower concentrations and higher polymer hydrolysis rates. This indicates better fluid distribution across multiple layers, leading to more stable oil production over time. The chemical composition of the produced polymer correlated with its residence time in the reservoir and matched well with the results of thermal stability tests conducted in the laboratory at reservoir temperature. This consistency suggests that the polymer’s integrity and effectiveness can be predicted based on its exposure to the reservoir’s thermal and chemical conditions. By integrating polymer concentration and composition data with field production results, this approach enables operators to identify areas of strong connectivity and to make targeted decisions for improving polymer flooding efficiency. Interventions such as selectively closing certain layers or performing conformance control treatments can optimize fluid distribution and enhance overall recovery. Furthermore, this methodology can be refined by incorporating tracer and ILT data, offering a more comprehensive understanding of reservoir dynamics. These insights provide a robust framework for optimizing polymer injection strategies in complex, heterogeneous reservoirs, ultimately maximizing polymer flooding efficiency.