A novel approach for wettability estimation in geological systems by fluid-solid interfacial area measurement using tracers

Wettability plays a vital role in many applications of flow in porous media and affects Darcy scale flow parameters by influencing the fluid-solid interfacial area. Therefore, quantifying the fluid-solid interfacial area can provide a way to measure wettability at the Darcy scale. Here, we experimentally explore a dual-tracer method, which can also be scaled to large geological reservoirs to quantify the fluid-solid interfacial area during the multiphase flow through a porous medium for different wetting conditions. Using our experiments, we demonstrate the influence of different saturations, wettability and flow conditions on the solid–liquid interfacial area. When oil is in the residual phase, we observe that the solid-water interfacial area increases with the increase in water saturation for the water-wet and mixed-wet cases. However, the water-solid interfacial area decreases with an increase in water saturation for the oil-wet case. We increase the water saturation by increasing the water flow rate; therefore, the anomalous behaviour seen in the oil-wet case can be attributed to the rearrangement of oil and water at higher water flow rates. When both oil and water are flowing, the solid-water interfacial area increases with water saturation for all the wettability cases and increases in water wettability as anticipated. Synopsis: Wettability measurements at Darcy-scale give a broad idea of overall subsurface wetting conditions for application in CO2 sequestration, ground-water remediation or oil recovery.