Enhanced oil recovery methods are becoming an important source of oil production of wells that have already been explored and, by these methods, of increase of the total volume of oil extracted. An important example is the injection of polymeric solutions after the injected water has reached the breakthrough point. In the present work an experimental apparatus was built in order to test the ability of enhanced oil recovery of polymeric solutions, composed by Xanthan Gum (XG) dissolved in distilled water. This apparatus consists of an idealized porous media made with small spheres inserted in a cylindrical cell and then filled with oil with the same viscosity as the petroleum found in Campos Basin (Rio de Janeiro, Brazil). As displacing fluid, we tested polymeric solutions of different concentrations of Xanthan Gum and these non-Newtonian fluids were characterized using a rotational rheometer. The resulting characterization has shown that increasing the concentration, not only the level of viscosity, but also the elasticity of the fluid increases. The shear-thinning behavior of the solution can be well captured by a power-law model. For higher concentrations the shear-thinning feature of the Xanthan Gum solution is more pronounced. We conducted an experimental procedure to mimic enhanced oil recovery process by first injecting water until the breakthrough point. Increasing the polymer concentration, the extra amount of oil recovered also increase. Theoretical and heuristic analyses show that in the shear dominated regions, the Xanthan Gum polymeric solutions do not increase pore efficiency, but increase sweep efficiency, while the extensional character of the polymeric solution seems to indicate that in extensional dominated regions the polymeric solutions play an important role on the oil recovery efficiency from both perspectives: pore and sweep efficiencies.
oil recovery; polymeric solution; porous media
