Development of Nanomontmorillonite-Reinforced Terpolymer Gels for High-Temperature Petroleum Reservoirs

Conventional terpolymer/polyethylenimine (TP/PEI) gel systems have excellent and controllable gel strength, making them popular gel systems for controlling excessive water production in ultrahigh-temperature reservoirs. To further enhance the strength of the gel, this article used nanomontmorillonite (nano-MMT) as a gel enhancer and investigated its influence mechanism on the gelation performance, rheological parameters, and temperature resistance of TP/PEI gel systems at 80 and 150 °C, respectively. Results show that the gel strength of conventional TP/PEI gels increased with increasing cross-linker PEI concentration at 80 °C. However, excessive cross-linking occurred in the gel system when the PEI concentration increased to 0.5% at 150 °C. Moreover, the addition of nano-MMT shortened the gelation time, and this effect became more significant at higher reaction temperatures. At the same time, the addition of nano-MMT increased the gel strength. When the amount of nano-MMT added was 0.1%, the gel strength and viscosity of the gel system reached their minimum values. It was because nano-MMT had hydroxyl groups that hindered the progress of the cross-linking reaction. When the concentration of nano-MMT was high, it filled in the microgrid and prevented the molecular structure skeleton from being destroyed by high-temperature thermal vibration. Therefore, the nano-MMT-reinforced TP/PEI gel system had high strength and good thermal stability and met the plugging strength requirements under high-temperature reservoir conditions. This study can further supplement the types of nanomaterial-reinforced TP/PEI gel systems and provide theoretical guidance for their further application in water management in high-temperature petroleum reservoirs.