Investigation of longitudinal and transverse dispersion in stable displacements with a high viscosity and density contrast between the fluids

Transverse and longitudinal dispersion in gravity stable, favourable viscosity ratio flows are investigated and compared with earlier data obtained for miscible fluids and for tracer flow. Data from laboratory measurements of longitudinal dispersion in low viscosity ratio (8.63 × 10−4) and high density contrast (471 kg m−3) displacements are compared with literature data for more modest viscosity ratios and density differences and with earlier theoretical analysis. The longitudinal dispersivity was reduced by a factor of 2 for flows influenced by gravity. This reduction was relatively insensitive to the magnitude of the density contrast and the flow rate, for Peclet numbers less than 100 and found to be consistent with earlier theoretical predictions. Additional transverse dispersion data was obtained for fluids with a density contrast of 225 kg m−3 and a matched viscosity ratio over a range of Peclet numbers (1 < Pe < 1000). A similar reduction in transverse dispersivity in gravity stable flow, independent of Peclet number, was observed and found to be consistent with observations in the literature for more modest density contrasts.