EOR Polymer Flooding Enlivening Through Updated Coreflood Experiments and Advanced Numerical Reservoir Simulation: A Comprehensive Case Study
Authors: Fiallos-Torres M. X. , Eras C. Bermeo P. , Orjuela J. , Rodas J. 
Published: September 2024

A 45-year-old oil field has achieved successful transition of its field development plan towards full-field waterflooding after high-volume operations, continuous surveillance, and strategic interventions. Currently, tertiary recovery is on the horizon to take over the waterflooding processes. This paper presents a comprehensive case study on the revitalization of polymer flooding strategies through the integration of advanced numerical reservoir simulation and chemical coreflood experiments to overcome complex reservoir conditions and recover its untapped oil potential.

The methodology included the holistic numerical simulation of the physical behavior of a tailored polymer flooding into the reservoir. First, this paper's authors revisited the coreflood results to not only establish expectations on incremental oil recoveries but to elucidate simulation inputs for the polymer rheology model and rock-retention constraints. Detailed analysis was placed on the brine and polymer characterization, its viscosity model, mechanical degradation, and fluid-rock interactions. Next, simulation scenarios focused on overcoming critical parameters such as injectivity and polymer breakthrough time and refining existing operational constraints to optimize oil recovery efficiency. Finally, conformance control methods were evaluated.

The proposed approach evaluates the benefits and limitations of sulfonic polyacrylamide HPAM (15-17 MM Daltons) polymer flooding in this high-temperature (210°F) mature reservoir through highly detailed reservoir simulation conducted on Intersect (IX). The final product was a comprehensive evaluation of enhanced oil recovery (EOR) polymer flooding as a mobility control agent to improve sweep and displacement efficiencies of current waterflooding processes of the entire field thanks to advanced numerical simulation workflows. The selected polymer showed thermal stability and aimed to reach 10 cp at 800 ppm Nevertheless, critical parameters such as injectivity losses, permeability reduction factor, and polymer adsorption were thoroughly evaluated in both laboratory and field scales. Laboratory coreflood results were appropriately fitted with numerical methods, which served as reservoir numerical simulator inputs. Residual resistance factors (RRF) and resulting adsorption isotherm showed a low polymer retention by dynamic simulation. Also, monitoring field pressure and polymer concentration provided useful insights about improved sweep and polymer retention associated with the polymer flood. As result, the reservoir of interest and brine conditions (salinity, temperature, permeability, RRF, dead pore space, among others) caused favorable additional production incremental volumes of about 17% with respect to secondary scenarios.

The fine-tuned simulation aided to de-risk the EOR technology and evaluate the possible benefits of a full-field expansion of polymer flooding. For instance, modeling the brine ionic concentration of the injected water and its interaction with the polymer was a novel feature of this study. Also, polymer retention and its characterization were tailored in the studied field for the first time by de-risking as many parameters as possible and finding the optimum injection strategies.