Abstract
A novel branched synthetic polymer capable of changing the relative permeability of water and oil in a formation was developed. The new polymer has the capacity to anchor to the sandstone formation, allowing it to endure production fluid flow.
Thermal aging tests were conducted to evaluate the thermal stability. Gravity column tests were established as a screening method to evaluate the polymer's capacity to impair water flow and to anchor to the formation. Laboratory core flow tests were conducted using sandstone cores plugs with an air permeability of 0.8 to 5 Darcies at 200°F. The polymer was evaluated as a near wellbore treatment and as a far field treatment by altering the injection direction of the polymer slug.
Results indicate that the polymer can reduce the permeability to water without significantly impairing the permeability to oil. The regain relative water permeability was less than 20% after the injection of a relative permeability modifier (RPM) polymer. The subsequent regain relative oil permeability was above 75% and the regain relative water permeability was less than 30% after the oil injection. Results also showed that the RPM polymer had similar performance regardless of the injection direction used. Moreover, pre-flushing the core with mutual solvent and surfactants before the polymer treatment did not have a significant effect on the performance of the polymer.
The capacity to selectively modify the water permeability makes it feasible to use this polymer in a near wellbore or in a far field treatment to reduce excessive water production. Moreover, the polymer can be applied without the use of a mutual solvent and surfactants, thereby reducing treatment costs.