Fluid displacement mechanisms by foam injection within a microfluidic matrix-fracture system

Abstract

In this study, the researchers visually investigated changes in the saturation of fluids and the oil recovery factor (RF) during foam injection in a two-dimensional matrix-fracture micromodel system. The effects of the 1) presence of oleic phase (comparison of the results of foam injection tests with and without oil), 2) viscous force (comparison of the results of foam and gas injection tests), and 3) gravity force (comparison of the results of gas/foam injection tests in vertical and horizontal states) were mechanistically studied. The results showed that the presence of oleic phase has the potential to cause foam to degrade at the beginning of the test. However, as the experiment advanced and oil saturation was reduced, foam injection resulted in the recovery of the fluid in the matrix. Pressure decline in the fracture due to the high viscosity of the foam acted as a driving force perpendicular to the fracture in the matrix and caused a viscous cross-flow leading to a dramatic increase in oil recovery. Although the gravity force reduced the foam stability due to the foam film drainage process and the gravity segregation of gas and surfactant solution, a comparison of the performances of gas and foam in the vertical state revealed the superiority of foam injection.