Investigating the Effect of Polymer Gels Swelling Phenomenon under Reservoir Conditions on Polymer Conformance Control Process

Abstract

Abstract High water cut and water influx into production wells has become a serious problem in producing oil. Polymer gels treatment has been applied widely for near well bore regions to reduce water production. In water shut - off process, effective permeability, permeability reduction after gels treatment plays an important role for evaluating the level of reducing water cut. However, under complex reservoir conditions including pH, salinity, high pressure, and temperature, the polymer gels behavior is significantly affected by those parameters, such as pH affects to the gel strength; the difference in salinity concentration between formation water and polymer solvent (water) causes swelling phenomenon by osmotic pressure. Moreover, due to the presenting of reservoir crude oil, the shrinking phenomenon of polymer gels is taken into account. The swelling and shrinking phenomenon affect extremely on blocking porous media. Laboratory experiments are carried out to perform these behaviors in batch system which is able to work at reservoir conditions. Two types of polymer with high and low molecular weight are used; chromium acetate is used as cross-linker agents. Several gels samples are tested in ambient and reservoir conditions (high pressure, high temperature, difference in salinity and pH) to investigate polymer gels behavior. These polymer gels samples are used in injecting into the sand-pack cores. Disproportional permeability reductions are measured with each polymer type. Experiment results showed that the percent of increment in volume reaches 25 % (within 72 hours) with high salinity of polymer solvent (3%) and low salinity of formation water (0.5%). The lowest increment occurs when differential salinity is 0 % and 0.5 %. Moreover, water permeability is reduced strongly (67% of reduction) while it has less effect to oil permeability (17.5% of reduction) after polymer gels treatment. These investigations are important in evaluating the effectiveness of water shut-off process.