The effect of evaporation on the interactions between the trapped and invading wetting phase fluids in the pore doublet micromodel

Evaporation could affect the pore-scale interaction between the residual and invading water and mass transfer of solute in porous media. In this study, we used the pore-doublet model (PDM) with dyed liquids to perform a series of imbibition-drainage-evaporation-imbibition micromodel experiments. The pore-doublet model consists of two channels having a common inlet and outlet, one of which has a segment with a shrinking width. The ratios of the channel widths in two different pore-doublet models were 1:4 and 2:4. The theory and experimental results show that the wetting phase was trapped in the channel with the shrinking segment after drainage. The velocity ratio of the menisci in two channels, which was highly dependent on the channel width ratio, controlled the length of the residual wetting phase. For the PDM with width ratio 1:4, the air had not been formed at any injection rate during the 2^nd wetting. For the PDM with width ratio 2:4, without evaporation, an air bubble was trapped on the upstream side of the residual wetting phase, but the residual and invading wetting phases contacted and mixed on the downstream side of the residual wetting phase during the 2^nd wetting. On the contrary, with evaporation after the drainage, the length of the residual wetting phase reduced, and air bubbles were trapped during the 2^nd wetting on both sides of the residual wetting phase. The air bubbles completely separated the residual and invading wetting phases. Nevertheless, our experimental results showed that the invading wetting phase was still able to pass through the trapped air bubbles and mixed with the residual wetting phase via the corner flow.