Design of fluorine-modified nanocrystalline cellulose achieving super gas-wetting alteration of reservoir cores

Abstract

In gas condensate reservoirs, liquid condensation near the wellbore region can break gas well deliverability when the pressure drops lower than dew point. Gas-wetting alteration is one of the potential approaches to overcome the difficulty. However, gas production remains restricted because the wettability of the core surface can only be altered from original liquid-wetting to neutral gas-wetting by traditional methods. Herein, fluorine-modified nanocrystalline cellulose is developed to achieve super gas-wetting alteration, increasing the contact angles of brine and decane on core surface from 22° and 0o to 153° and 142°, respectively. This product not only reduces the surface free energy from 68.41 mN/m to 0.35 mN/m but also increases the surface roughness from 68.23 nm to 154.51 nm. The capillary tube and imbibition experiments further confirm that the wettability of the core surface has been altered from strong liquid-wetting to super gas-wetting. This result indicates that the liquid is easier to peel from the core surface to improve the ability of transportation and distribution. Besides, after the super gas-wetting alteration, the required pressure for displacement is reduced and the core permeability is restored dramatically. Meanwhile, it has been proved that fluorine-modified cellulose is more suitable for unconventional low permeability reservoirs. This work also reveals the mechanism of super gas-wetting alteration in detail, which will expand the better application of the material in more oilfields and other mining engineering developments.