| Abstract: | Profile modification of injection wells or water plugging of production wells are the most common ways to improve oil recovery with the continuous development of oil reservoirs. For high temperature and high-salt oil and gas reservoirs, the plugging agent is required to have certain stability under high temperature and high-salt conditions. Polymer gel is one of the commonly used plugging agents in oil fields. This article conducted detailed experimental research and mechanism analysis on six gel systems composed by two types of polymer (hydrolyzed polyacrylamide [HPAM] and terpolymer L-1) and three types of cross-linker systems (phenol/hexamethylenetetramine [HMTA], resorcinol/HMTA and bisphenol-A/HMTA). The mechanisms of cross-linker systems and polymer were studied, and the experimental researches were done on their gelation process, long-term thermal stability, salt resistance, microstructure observation, rheological properties, and so on. The number of high-temperature resistant cross-linking points determines the performance of the gel system formed by cross-linker systems with the polymer. The cross-linker systems of bisphenol-A/HMTA have four high-temperature resistant cross-linking points, and its performance was the best. Due to the introduction of ATBS and NVP groups on the polymer chain, the performance of gel system formed by the terpolymer L-1 was significantly more stable than that of formed by HPAM. This study shows that the bisphenol-A/HMTA-L-1 gel has excellent long-term thermal stability and salt tolerance, and can be used in ultrahigh temperature (150°C) and high-salt oil and gas reservoirs to improve oil recovery. |
