Low Dosage Novel Surfactant Technology for Improving Polymer Injectivity in Atlee Buffalo Oil Pools
Authors: He Kai , Tran Trinh , Roostapour Alireza , Tudor Eric , Moradi Mehrnoosh , Gilmer Chad , Ramsden-Wood Ashley 
Published: April 2024

For a successful polymer EOR application, maintaining high polymer injectivity below fracture pressure is important to prevent fracture propagation in the reservoir causing fast breakthrough. Adding surfactant into the polymer system can facilitate the reduction of interfacial tension between injected fluids and reservoir oil, enabling more efficient oil displacement and enhanced sweep efficiency. Additionally, tailored surfactant can modify rock wettability and mitigate polymer retention in the reservoir, and thereby improve polymer injectivity and well production.

In this work, a detailed surfactant selection workflow and key strategies are presented to evaluate the efficiency of surfactants in improving polymer injectivity for the Atlee Buffalo oil pools in Canada. Laboratory analyses encompassed fluid characterization, interfacial tension (IFT), emulsion tendency, and polymer compatibility. These preliminary tests enabled the pre-screening of surfactants and the optimization of surfactant dosages. To further validate surfactant performance, core flood (CF) experiments were conducted using sandstone cores that closely resembled the reservoir's permeability and mineralogy. The CF employed a meticulously designed injection scheme to evaluate the impact of surfactants on improving polymer injectivity.

Given the low dosage application strategy, it is imperative to choose a surfactant that can consistently maintain a low IFT at low surfactant concentrations. The preliminary IFT scans revealed that novel surfactant could maintain IFT from 0.15 to 0.43 mN/m for different pool oils at low concentrations. Furthermore, additional testing has confirmed that the surfactant does not induce any tight emulsions, thereby mitigating surface-related complications during production. Viscosity measurements have indicated that the surfactant has no discernible impact on the fluid viscosity influenced by the polymer, demonstrating the compatibility between the polymer and surfactant solution. Significantly, in the multiphase CF tests, it was evident that the selected surfactant led to an approximate 2.8 to 4.2 times enhancement in injectivity during polymer flooding. Moreover, under the protective influence of surfactant, injectivity loss was four times slower during polymer flooding when oil saturation dropped below 30%. Furthermore, by combining the low-dosage surfactant with polymer, an additional 15.3% oil recovery was observed after polymer injection alone. These results underscore the substantial benefits of adding novel surfactant in improving injectivity and overall oil recovery.

In contrast to conventional surfactant-polymer flooding, this study explores a strategy of applying a low dosage surfactant to enhance polymer injectivity. By properly tailoring the surfactant, this approach harnesses the synergy between surfactant and polymer to address the challenges posed by high viscosity oil reservoir. Notably, after conducting a field trial in an Atlee Buffalo oil pool with the recommended low dosage surfactant, injection data demonstrates that it can stabilize and improve the polymer injection process.