Combined effect of Bond and capillary numbers on hydrocarbon mobility in water saturated porous media

The mobilization of an oil bank under the combined effect of Bond (N_B) and capillary (N_C) numbers, in a packed bed column of glass beads saturated with water, has been investigated. In order to reach the irreducible saturation the experiments have been run with sweeping water velocities outside the range of validity of the Darcy's law. The size of the glass beadswas varied in the range between 2 mm and 5 mm. The oils used for the tests are hexadecane and hexane with viscosities different for an order of magnitude and densities smaller than that of water, and a-methylnaphthalene, which has a density very close to that of water, in order to single out the effect of the capillary number on the mobilization process. The plots of oil saturation as function of the trapping number (N_T), which is the vectorial sum of N_B and N_C, are reported and a mobilization diagram is drawn. Furthermore, a few tests in a basin, simulating an aquifer at a laboratory scale, have proved that the results obtained in the packed column are useful for determining the fate of a spill of oil above an aquifer. For these experiments also perchloroethylene (PCE), which has a density greater than that of water, has been used.