Evaluation of the Water-Blocking Performance of Polyurethane Plugging System and Urea-Formaldehyde Plugging System in Xinjiang Oilfield.

Water channeling during water injection in mid-to-late development stages of low-permeability reservoirs in Xinjiang leads to a rapid water cut increase and reduced oil displacement efficiency, causing significant economic losses. This study systematically investigated two chemical systems-a polyurethane (PU) plugging system and a urea-formaldehyde (UF) plugging system-under simulated Xinjiang reservoir conditions. The PU plugging system formulation was optimized through control variable experiments, and both systems were evaluated for rheological properties, curing behavior, mechanical strength, salinity and temperature adaptability, and plugging performance using sand-pack displacement tests. The optimized PU plugging system cured at 80 °C for 1 h achieved a maximum plugging rate of 96% and a breakthrough pressure gradient of 4.2 MPa·m-1. The UF plugging system exhibited distinct temperature-triggered gelation, with viscosity rising exponentially above 60 °C, providing a plugging rate of 70% and a breakthrough pressure gradient of 1.0-2.0 MPa·m-1, suitable for deep fluid diversion. The PU plugging system offers high-strength near-wellbore plugging, while the UF plugging system enables controllable deep fluid diversion. Their complementary properties provide a comprehensive technical strategy for water channeling control in different low-permeability and high-temperature reservoirs in Xinjiang Oilfield.