VISCOUS FINGERING IN 5-SPOT EXPERIMENTAL POROUS-MEDIA - NEW EXPERIMENTAL RESULTS AND NUMERICAL-SIMULATION

This paper reports new experimental and numerical results on miscible displacements in saturated, homogeneous five-spot bead-packed how mode ls. A series of experimental floods at a range of mobility ratios is p resented which generates new data for unstable displacement processes. These data are presented up to 100% recovery and they include the fol lowing: the effluent concentrations and recovery profiles, in situ vis ualisation of the flow patterns and measurement of the pressure field. A comparable cycle of hoods at mobility ratios of approximately M = 4 , 11 and 25 in st repacked five-spot system showed excellent reproduci bility between tests. The volumetric displacement efficiencies compare very well with the published experimental data where this is availabl e. The measurement of the pressure held is particularly novel and this information can be utilised in order to assess averaged (upscaled) mo dels of viscous instability. A high-accuracy numerical method with thi rd-order differencing for convection and second-order temporal differe ncing is proposed which is equivalent to an Ii-point interpolation. Th e simulator treats the full velocity-dependent anisotropic diffusion/d ispersion tensor and is validated by comparing numerical results with the analytical solution for incompressible radial flow. The numerical method has been used to simulate the experimental five-spot stable and unstable displacements. The simulation reproduces the experimental ef fluent concentrations, recovery performances and pressure drops very w ell and also matches the main features of the experimental finger evol ution. The central novel contributions of this paper are that (i) a co mplete qualitative experimental data set, including novel pressure hel d measurements, has been obtained up to 100% recovery which can be use d to validate theoretical models of viscous fingering in five-spot (al most) homogeneous systems; and (ii) a numerical scheme is presented wh ich is capable of accurately simulating the hows characterised by inst ability and low levels of physical dispersion in this 'difficult' geom etry. Copyright (C) 1996 Elsevier Science Ltd