Integrated reservoir stimulation with polyacrylamide hydrogels and surfactant solutions for oil recovery enhancement

The compound system of polyacrylamide hydrogels and surfactant solutions are used for enhanced oil recovery (EOR). The polyacrylamide hydrogels are injected into block high-permeability zones firstly, followed by a low-cost sacrificial agent, then an oil-displacing surfactant, and finally an aqueous polymer solution containing diethanolamine, to enhance oil production. The hydrogels are selected through oscillatory rheometry, while the surfactant is optimized after optical imaging analysis. The EOR performance of the compound system is evaluated through core flooding experiments and reservoir numerical simulation. Specifically, the properly cross-linked polyacrylamide hydrogel can be selected using its elastic modulus as a quantitative parameter while accounting for pore structure. The sacrificial agent is used to block active adsorption sites in the rock matrix before mobilizing more crude oil with a nonionic-anionic surfactant system. The addition of the mild organic alkali (diethanolamine) into the polymer slug reduces surfactant adsorption and improves sweep efficiency, thereby enhancing the oil-washing effect. Flooding experimental results show that the sequential injection of hydrogel and surfactant compositions prolongs the period of increasing pressure gradient during subsequent waterflooding and significantly boosts oil production, achieving a 21-percentage-point increase in oil displacement efficiency. Numerical simulation for the target reservoir in the West Siberian oil province confirms the effectiveness, projecting a maximum cumulative oil increase of 6 851 t over three years.