Development of Agar-Based Preformed Particle Gel for Water Control in High-Salinity Reservoirs

Oil extraction faces challenges in cost and complexity due to excessive water production, leading to diminished hydrocarbon recovery. Preformed particle gels (PPGs) hold promise for enhancing oil recovery and sealing high-permeability or fractured zones. However, current PPGs encounter limitations in high-temperature reservoirs, including salt sensitivity and potential hazards. To address these issues, we propose eco-friendly PPGs utilizing agar polysaccharides. Agar backbones grafted with acrylamide (AM) and AM/N,N′-methylenebis(AM) (MBA) via microwave-assisted techniques resulted in polyacrylamide grafted agar (Ag/PAM) and cross-linked polyacrylamide grafted agar (Ag/PAMBA). Various sizes (75 μm to 1.18 mm) were prepared to accommodate diverse reservoir porosities and ensure effective plugging of fractures. Characterization techniques such as Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscope, swelling measurement, particle size analysis, and rheology were employed. Results demonstrate that Ag/PAM-based PPGs exhibited high absorbency in high saline water (TDS = 67.3 g/L), with swelling ratios ranging from 8.4 to 19.2 g/g. Salt sensitivity factors (f) confirm that salinity increases the swelling ratio for all of the prepared PPGs. Swollen particle sizes were well-controlled within the ranges of 136 μm and 2.9 mm. Factors affecting absorbency and strength, including pH, temperature, and aging were investigated and discussed by considering the structures of both materials. Ag/PAMBA displayed excellent resistance to temperatures up to 130 °C, with a storage modulus between 10 and 32 kPa, surpassing commercial PPGs. Core flooding experiments revealed the good plugging efficiency of open fractures in sandstone cores using an agar-based material. Core flooding results showed that Agar-based-PPG has good plugging efficiency in the open fracture model with a water breakthrough pressure of approximately 108.9 kPa (778 kPa/m). The outstanding performance of the prepared PPGs positions them as promising options for both low- and high-temperature reservoirs in oil recovery applications.