Investigation of EOR Formulations with Engineered Brines Utilizing Bespoke Polymer for a Candidate Offshore Heterogeneous Sandstone Reservoir

Polymer flooding, a proven Enhanced Oil Recovery (EOR) method, often encounters challenges in harsh reservoir conditions such as high salinity with divalent ions. Herein, this study developed engineered brines with varying divalent content combined with low concentrations of a formulated polyacrylamide-based co-polymer, which has shear-thickening feature, suitable for harsh conditions in a candidate field. This novel polymer was evaluated and compared with the HPAM utilizing a wide range of injection brines. An extensive evaluation of reservoir characterization, including petrophysical property analysis, conventional core analysis, and fluid–fluid analysis, was conducted. Moreover, formation damage tests were conducted to evaluate the brine's compatibility with the respective formation. After that, several polymer evaluation studies, including polymer screening, rheological tests, and displacement efficiency tests, were also conducted through the coreflooding experiments to investigate the performance of bespoke EOR formulations under representative reservoir conditions tackling the multiple zones of heterogeneity. The coreflooding resulted in a cumulative oil displacement efficiency of 40% during waterflooding (candidate field seawater SW, base brine) compared to 53% with SW-based HPAM. The hybrid EOR approach utilizing the softened engineered brines in conjunction with the bespoke polyacrylamide-based co-polymer resulted in cumulative oil displacement efficiency of up to 63% while delaying the water breakthrough time by up to two times. This study demonstrates the potential of achieving significantly increased performance utilizing the proposed EOR in the candidate reservoir across the entire encountered range of heterogeneity.