Abstract
Oil recovery resulting from Alkaline-Surfactant-Polymer (ASP) flooding is mainly due to the improvement in sweep efficiency by the action of the chemicals. The alkaline modifies the wettability of the reservoir rock and generates in-situ surfactants, the surfactant impairs the capillary pressure between water and oil in the reservoir, while the polymer increases the viscosity of the mobilizing slug and improves mobility ratio. The resulting effect therefore is an improvement in volumetric sweep efficiency, which in turn leads to higher oil recovery.
This work presents an experimental study of ASP flooding. Four methods classified as A, B, C and D were studied. Method “A” involving the mixture of Sodium Hydroxide, Lauryl sulphate and Gum Arabic to form an ASP slug resulted to further oil recovery of 7.1% of the Initial Oil in Place(IOIP). Method “B” (Sodium Hydroxide Pre-flush before Lauryl sulphate and Gum Arabic slug) gave an oil recovery of 7.9% IOIP. Method “C” (Sodium Hydroxide, Lauryl sulphate Pre-flush, Gum Arabic) had an oil recovery of 6.3% IOIP. While Method “D” (Lauryl Sulphate pre-flush before Sodium Hydroxide and Gum Arabic slug)recovered7.6% IOIP.
The results of the experimental study show that the usage of an alkaline as pre-flush and a mixture of surfactant and polymer to flood yield a much greater oil recovery. This reveals that the effectiveness of an ASP flooding is dependent on the mechanism employed in implementing the flooding process.
