Effect of a hydrophobically associating polymer on disproportionate permeability reduction to oil and water for sandstone reservoirs

Because of the absence of amphiphilic, the disproportionate permeability reduction (DPR) performance of the traditional partially hydrolyzed polyacrylamide (PHPAM) or PHPAM-based gel in oil-wet sandstone reservoirs is barely satisfactory. Therefore, this study proposed a hydrophobically modified polyacrylamide (HMPAM) with amphiphilic in nature, and a series of experiments were performed on both water-wet and oil-wet sandstone core samples to investigate the DPR potential of it. According to the core flooding experiments, HMPAM flooding could reduce the water permeability of oil-wet cores by 93%, and only about 20% permeability reduction can be observed for the oil phase, showing the good DPR performance. In contrast, the traditional PHPAM had no obvious DPR effect on the oil-wet core. The big difference of DPR performance can be attributed to the gap between HMPAM and PHPAM in the adsorption capacity on sandstone surface. For oil-wet sandstones, the adsorption of HMPAM was 5.16 mg/g, while there was only 1.22 mg/g for PHPAM. The adsorption of HMPAM can narrow the pore throats and alter the wettability of the oil-wet rock surface, increasing the flow resistance of water, while hardly affecting the oil flow.