Dual-Scale Engineered Poly(acrylamide-calcium alginate) Microspheres for Enhanced Oil Recovery in Heterogeneous Low-Permeability Reservoirs

While cross-linked polyacrylamide (PAM) microspheres demonstrate viscosification and thermal stability in conventional reservoirs, their efficacy diminishes in low-permeability heterogeneous formations where confined oil exists as persistent films and blind-channel networks. Here, we report a novel oil recovery agent, poly(acrylamide-calcium alginate) [(P(AM-CaAlg)] microspheres, prepared via a two-step emulsion-ion double network cross-linking polymerization strategy that synergistically integrates PAM’s macroscale fluid dynamics with alginate’s molecular-level interfacial engineering. Experimental and simulation analyses demonstrate that P(AM-CaAlg) uniquely combines: (1) preserved PAM-like dynamic rheological behavior, ensuring macroscopic displacement efficiency, and (2) alginate molecular chain-induced superior interfacial activity and static viscoelasticity at the microscale. This dual-scale functionality enables deeper penetration into low-permeability zones and stronger oil film detachment, achieving a 6.48% higher recovery rate than PAM. This approach introduces biodegradable alginate components for enhanced oil recovery, establishing a green, cost-effective paradigm for sustainable oil recovery in complex reservoirs.