Abstract
The influence of flow velocity and core heterogeneity on foam flow through porous media has been investigated with the aid of X-ray computed tomography (CT). The real time imaging of fluid partitioning, the saturation profiles extracted from the CT images and the pressure drops over several core segments have been analyzed in the light of a mechanism involving capillary and viscous forces. Natural Bentheim and Berea sandstone cores together with nitrogen (N2) foam, stabilized using sodium dodecyl sulfonate (SDS) have been used to conduct the experiments. Geological layering of Berea sandstone was oriented either parallel or perpendicular to flow.
The transient foam flow in cores containing a surfactant solution exhibits a front-like character. The secondary liquid desaturation reported previously is barely modified by increasing foam quality and leads to the same final liquid saturation of 20% near the core outlet. However, upon increasing simultaneously the liquid and gas injection rates (at constant foam quality) the secondary desaturation is enhanced, resulting in a lower final liquid saturation. For the cores having a layering parallel to flow the secondary desaturation is relatively stronger but the final liquid saturation remains higher. A completely different fluid distribution is obtained for cores having a layering perpendicular to the flow direction due to a capillary entrapment phenomenon. The final liquid saturation far from core inlet is identical to that of homogeneous core. However, the pressure drop is considerably lower suggesting that foam flows under a coalescence regime.
