Polyacrylamide gel formed by Cr(III) and phenolic resin for water control in high-temperature reservoirs

A polyacrylamide gel formed by Cr(III) and phenolic resin was developed and systematically evaluated for water management in extremely high-temperature reservoirs. The gels were cross-linked by both covalent and coordination bonds. Through the gel strength code method, the polyacrylamide gels cross-linked with both Cr(III) and phenolic resin had good thermal stability compared to that of gels formed in the presence of either cross-linker alone. The polyacrylamide gel was heated at 140 °C for 120 days without any occurrence of syneresis with its strength remaining at code H. The microstructure of the gel was studied by scanning electron microscopy (SEM), which indicated that the spherical structure formed by the composite cross-linker can strengthen the dendritic structure to increase the strength and temperature resistance of the gel, explaining the mechanism of improvement of the thermal stability of the gel. The differential scanning calorimetry (DSC) experiments confirmed that the temperature resistance of the composite cross-linked gel persists even at a high temperature of 140 °C. The improved three-dimensional network firmly locks water within the gel even under extremely high temperatures. This study suggests that the polyacrylamide gel formed by Cr(III) and phenolic resin has good thermal stability and can be applied to enhance oil recovery in high-temperature reservoirs.