Experimental approach to measure capillary associated interfacial area using kinetic interface sensitive tracers in a simultaneous two-phase flow

The kinetic interface sensitive (KIS) tracers have been the focus of research in the past decade, as a new, reactive tracer method to estimate the interfacial area between immiscible fluids in porous media. We present here a novel experimental approach to measure the capillary associated fluid-fluid interfacial area using the KIS tracers in simultaneous two-phase flow conditions. The new approach is applied in a sand column filled with glass-beads (d₅₀ = 170µm). Four laboratory experiments are performed in a simultaneous two-phase injection scheme using different fractional flow ratios (Flow rate of wetting phase: total flow rate). The different fractional ratios create different saturations inside the column, which correlate to different fluid-fluid interfacial areas. The new method, introduces also a new analytical method to handle reacted by-product concentration data acquired, different from the KIS tracer method in dynamic conditions. By comparing the results to other established techniques reported in the literature (i.e., interfacial partitioning tracer test and computed micro-tomography) used to measure fluid-fluid interfacial area we observe a good agreement.  The capillary associated interfacial area increases with decreasing wetting saturation until a maximum value, which then drops near the residual saturation. The maximum capillary associated interfacial area occurs at wetting saturation ranges between 0.45 < S_w < 0.6, which is slightly shifted towards the higher wetting saturation when compared to the other techniques. Furthermore, the results are simulated using a Darcy-scale reactive transport multiphase flow in porous media numerical model.