The growing demand for energy and stricter environmental regulations necessitate the adoption of sustainable oil recovery methods, particularly in high-salinity, high-temperature (HSHT) reservoirs, where conventional synthetic polymers often suffer from viscosity loss, thermal degradation, and precipitation. This study evaluated a novel biopolymer extracted from orange peel waste as a cost-effective and environmentally benign alternative for polymer flooding under HSHT conditions. The biopolymer was produced through an optimized extraction process and characterized in terms of viscosity, thermal stability, and interfacial properties. Core flooding experiments were performed on Berea and Saq sandstone cores at 90 °C and 165,000 ppm salinity under three injection scenarios: conventional waterflooding (base case), polymer injection immediately after water breakthrough (WBT), and early polymer injection before significant water production. Citrus-based biopolymer maintained adequate viscosity at reservoir temperature and reduced oil–water interfacial tension from 21.8 to 8.59 mN/m; however, the primary recovery mechanism for the present formulation is mobility control rather than ultralow-IFT mobilization. In Berea sandstone, ultimate oil recovery increased from 47.6% in the base case to 51.7% and 63.35% when polymer was injected after WBT and at an early stage, respectively. For Saq sandstone, early polymer injection increased final oil recovery from 46.2% to 70.3% relative to the base case. These results correspond to incremental gains of approximately 15.8 and 24.1% points of OOIP relative to the respective base-case waterfloods in Berea and Saq cores. Overall, the findings demonstrated that citrus-derived biopolymers would address key limitations of conventional polymers in HSHT reservoirs while valorizing an abundant agricultural waste stream and supporting circular-economy principles.
Ali et al. (Fri,) studied this question.