Summary Polymer flooding, a widely recognized method for enhanced oil recovery (EOR), is often hindered by harsh reservoir conditions, particularly those containing elevated levels of divalent cations. The aim of this study is to experimentally investigate the EOR mechanisms of hybrid-engineered brine shear-thickening copolymer flooding, specifically the shear-thickening feature of bespoke polymer and its impact on oil recovery under such conditions (salinity: 208,776.3 mg/L). The initial bulk rheology test identified four distinct shear-thinning and thickening regimes, establishing injection rates for oil displacement efficiency (DE) tests across three outcrops. These rates were selected to encompass the transition spectrum between the identified flow regimes for each outcrop. Additionally, nuclear magnetic resonance (NMR) measurements evaluated pore size changes pre- and post-flooding, highlighting polymer retention effects. In the oil DE test, the polymer injected at flow rates aligned with the identified shear-thickening regime demonstrated the highest oil recovery (63.64%) compared with other polymer flooding tests on different outcrops utilizing shear-thinning flow rates. This test also exhibited a significantly delayed water breakthrough time and reduced subsequent water production attributed to the successful in-situ self-diversion capability of the shear-thickening hybrid-EOR (HEOR) polymer, which effectively diverted flow toward unswept zones. Simultaneously, this injection yielded the highest residual resistance factor (RRF) value (1.70). In addition, the thorough NMR assessment of pore body changes in the mentioned outcrop revealed that the polymer occupied the most significant portion of mesoporous bodies (32.48%) compared with other polymer flooding tests. This finding indicates increased displacement of recoverable oil under the optimized flow rate, showcasing the polymer’s shear-thickening feature. Furthermore, a consistent correlation was found between mesoporous changes and RRF results across all three polymer flooding tests. The research demonstrates that mesopore occupancy signifies the polymer’s shear-thickening properties, reflected in the RRF, and effectively targets previously bypassed oil. By integrating NMR technology and mapping four distinct shear-thinning and -thickening regimes, we establish conclusive evidence of the bespoke polymer’s potential to significantly enhance oil recovery through its shear-thickening behavior. This is achieved by effectively delaying water breakthrough and reducing water production due to successful in-situ self-diversion of the HEOR shear-thickening bespoke polymer.
Nugrahaningtyas et al. (Mon,) studied this question.