Experimental and Theoretical Investigation of Glycol-Based Hydrogels through Waterflooding Processes in Oil Reservoirs Using Molecular Dynamics and Dissipative Particle Dynamics Simulation

Abstract

Enhanced oil processing aims to retrieve petroleum fluids from depleted reservoirs after traditional processing. Hydrogels and polymeric macromolecules are considered effective displacing agents in oil reservoirs. In the current work, the authors used hydrophilic hydrogels based on poly(ethylene glycol)/poly(propylene glycol) (PEG/PPG) surfmers for oil displacement processes. Statistical modeling of the rheological properties at 80 °C for the two hydrogels indicates that the viscosity–shearing profile obeys the power-law model. Also, shear stress scanning follows the Herschel–Bulkley and the Bingham plastic models. The two hydrogels exhibit an initial yield stress owing to the formation of a three-dimensional (3D) structure at zero shearings. Furthermore, PEG and PPG hydrogels can retain the viscosity after a shear rate of 64.68 S ^–1. On the scale of surface activity, the two hydrogels exhibit higher surface areas ( A _m) of 0.1088 and 0.1058 nm ² and lower surface excess concentrations (Γ _m) of 1.529 and 1.567 × 10 ¹⁰ mol/cm ², respectively. A molecular dynamics (MD) simulation was conducted to explore the Flory–Huggins chi parameter, the solubility parameter, and the cohesive energy density. The results indicate a negative magnitude of chi parameter (χ _ij ) for water and salt, which indicates that the two hydrogels have a good tendency toward saline formation water in the underground petroleum reservoir. Furthermore, the dissipative particle dynamics (DPD) was performed on a mesoscale to investigate the interfacial tension, the radius of gyration, the concentration profile, and the radial distribution function. The increased radius of gyration ( R _g) confirms that the two hydrogels are more overextended and can align perpendicularly toward the water/oil boundary. Experimental displacement was operated on a linear sandpack model using different slug concentrations. The oil recovery factor, the water-cut, and the differential pressure data during the flooding process were estimated as a function of the injected pore volume. The obtained results show that the oil recovery factor reaches 72 and 88% in the cases of PEG and PPG hydrogels at 80 °C with concentrations of 1.0 and 1.5 g/L, which reveals that both hydrogels are effective enhanced oil recovery (EOR) agents for the depleted reservoirs. This study establishes a new route that employs MD and DPD simulation in the field of enhanced oil recovery and the petroleum industry.