It is well-known that the production of gas-condensate reservoirs is significantly affected by the liquid condensation near the wellbore region. Gas-wetting alteration can be one of the most effective approaches to alleviate condensate accumulation and improve liquid distribution. However, gas well deliverability is still limited because the wettability of cores is altered only from liquid-wetting to intermediate gas-wetting by using traditional chemical stimulation. To solve this bottleneck problem, herein, we developed a fluorine-functionalized nanosilica to achieve super gas-wetting alteration, increasing the contact angles of water and n-hexadecane on the treated core surface from 23 and 0° to 157 and 145°, respectively. The surface free energy reduces rapidly from 67.97 to 0.23 mN/m. The super gas-wetting adsorption layer on the core surface formed by functionalized nanosilica not only increases the surface roughness but also reduces the surface free energy. The core flooding confirms that the required pressure for displacement is apparently reduced. Meanwhile, the core permeability can be dramatically restored after the super gas-wetting alteration. The microscopic visualization is employed to further understand the impact of fluorine-functionalized nanosilica on the fluid flow behavior and mechanism in porous media. The oil saturation in the micromodel decreases sharply from 48.75 to 7.84%, eliminating the "water locking effect" and "Jiamin effect", which indicates that the added functional nanosilica effectively improves fluid flow capacity and may contribute to production in the gas condensate reservoirs. In addition, this work reveals the fluid flow behavior and mechanism in the reservoir in detail, which will expand the better application of this material to many oilfields and other mining engineering systems.
Keywords: contact angle; fluid flow capacity; fluorine-functionalized nanosilica; oil saturation; super gas-wetting alteration.