Gravity segregation at the pore scale in cores under miscible and low interfacial tension conditions including in-situ tomography

Gravity effects at the pore/core scale have been examined in two sets of experiments. The first used uniform-sized beadpacks and visual observations and the second core material and CT scanning. The uniform beadpacks were flooded with a fluid mixture which could be conditioned to form 2 phases in situ. The interfacial tension and density difference were controlled by varying the temperature. Fluid segregation due to density difference, pore size and interfacial tension and thus a function of Bond Number, was studied. Experiments with the wetting and the non-wetting phase in the majority were included. In the CT scanning experiments, a uniform alumina core had a horizontal miscible displacement performed in it and the displacement was followed by regular CT scanning along the core. Then two static phases (using a fluid system similar to the one used for the beadpacks) were formed in situ within the core, and the positions and saturation of wetting and non-wetting phases observed over a period of time (similar to 24 h). The effects of gravity cannot be fully correlated by the current definition of Bond Number; saturation influence has to be added. If gravity effects are neglected during the interpretation of core test data errors can be created when using the results for reservoir engineering purposes: for example in dispersion calculations, relative permeability estimations and scale-up predictions.