Wettability enhancement of hydrophobic artificial sandstones by using the pulsed microwave plasma jet

We report that the wettability of artificial sandstones can be significantly improved by an innovative pulsed microwave plasma jet (PMPJ). The roughness of the sandstone surface is enhanced after the PMPJ treatment, but according to the Wenzel model, it has the negative effect to make a hydrophobic surface become hydrophilic. The molecular dynamics (MD) simulation shows that the alteration of the surface chemical property has a positive effect on the hydrophilicity enhancement, whose influence can compensate for that of the roughness. It is these two factors together that make the hydrophobicity of the sandstone become weaker after the PMPJ treatment. These findings hold great potentials in petroleum engineering, which may provide some inspirations for the enhancement of oil/gas recovery by the plasma technology.