Abstract
Polymer flooding improves the mobility ratio by mainly increasing the injected water viscosity. Typically, these projects minimize the volume of polymer due to economic aspects since the polymer cost significantly affects operation expenditures. However, the injection of a single slug sometimes produces an abrupt viscosity transition at the slug tail, and the chase water forms fingers that can bypass the slug, destroying its integrity. Injecting gradually more dilute slugs mitigates viscous fingering and reduces polymer mass. The scarce field applications, scarce testing at laboratory scale, and the absence of simulations discussion drove the interest in the subject. This study implements and evaluates a numerical simulation by integrating laboratory scale data - bulk rheology, single- and two-phase core floodings - and then history matching graded viscosity core flooding. The results were compared using performance indicators and validated with three laboratory experiments from the literature. The experiments consist of one continuous injection core flood and two core floods using grading viscosity with similar polymer injected mass, one with two slugs and another with three polymer slugs. Experimental and simulated history data for oil recovery and cumulative water matched with less than 5% of normalized error. Events such as water and polymer breakthroughs were well represented. The performance indicators revealed the three slugs test showed the best polymer utility factor for oil/water and best injectivity. On the other hand, the two slugs test reached higher final incremental oil recovery. This work contributes to data integration and extended discussions necessary to enable tailoring and motivating applications of polymer viscosity grading, to save polymer mass and reduce the produced water.
NSTL