Preparation of fluoropolymer nanoparticles(FPNPs) dispersion and its application as a wetting adjustment agent for sandstone rocks

In this paper, a kind of fluoropolymer nanoparticles (FPNPs) with excellent dispensability and stability was prepared for sandstone wettability adjustment. FPNPs not only could adsorb on sandstone to form micro-nano structures but also reduce the surface free energy of sandstone. FPNPs could change the wettability of cores from super-hydrophilic to superhydrophobic. The formation water contact angle of cores from 7 degrees to 150 degrees (95.33 % in wettability alteration). The surface free energy of cores from 180.77 mN m(-1) to 0.817 mN m(-1) (99.54 % reduction). The temperature resistance experiments illustrate that the formation water contact angle was 139 degrees after 48 h aging at 150 degrees C, which is still a highly hydrophobic state. Ultrasonic cleaning experiments explain that after 45 min of ultrasonic cleaning, the formation water contact angle was 131 degrees, indicating that there is a strong adsorption force between the core and FPNPs. Core imbibition experiments demonstrate that the treated core imbibition rate reduced by 66 %. Core flooding experiments show that the core water permeability increased by 44.26 %, and the pressure reduction rate reached 29.62 %. Therefore, FPNPs have promising applications in the fields of removing water locking, reducing injection pressure, and increasing injection volume. (C) 2021 Elsevier Ltd. All rights reserved.