Preparation and characterization of super hydrophobic/oleophobic material and its application in releasing liquid locking in tight condensate gas reservoirs

In this paper, a super hydrophobic/oleophobic material CS-1 with super hydrophobic/oleophobic properties was successfully prepared with nano silica as the main raw material and 1H, 1H, 2H, 2H-perfluorooctyl trichlorosilane as modifier. The structures of synthesized product were characterized by the infrared spectroscopy (FTIR). The contact angle of super hydrophobic/oleophobic material CS-1 was measured by contact angle measuring instrument, and its hydrophobic/oleophobic properties were analyzed systematically. The micro-morphology of super hydrophobic/oleophobic material CS-1 was determined by scanning electron microscope. The results of wetting properties show that the maximum water phase contact angle of hydrophobic/oleophobic material CS-1 is 159.58° and the maximum oil phase contact angle is 135.63°. Based on triple action of constructing micro-nanostructure on rock surface, reducing gas-water surface tension and oil-water interfacial tension, the optimized formula of the unlocking agent 1.5 wt% super hydrophobic/oleophobic material CS-1 + 0.06 wt% NFS surfactant +0.09 wt% C3 Gemini surfactant was screened by single factor method. Finally, the performance of unlocking agent is comprehensively evaluated by surface energy spectrometer, laser particle size analyzer, automatic contact angle tester and core unlocking equipment. The results show that the water phase contact angles of the core treated with the unlocking agent are greater than 150° and the oil phase contact angles are greater than 130° in acidic, alkaline and high temperature environments. The maximum recovery rate of water locking damage gas measurement permeability is 91.1%, and the maximum recovery rate of oil locking damage gas measurement permeability is 67.4%. It shows that the unlocking agent can effectively improve the gas logging permeability of the core and change the wettability of the core surface, so as to relieve the liquid locking of the condensate gas reservoir. It has a good application prospect in the middle and late stage of condensate gas reservoir development.