Construction Of Superhydrophobic Surface And Its Application In Profile Control And Water Shutoff

In order to mitigate several disadvantages induced by conventional technologies involving difficulty to locate water yield formation,tendency to plug pay zone and low stimulation efficiency,inspired by the fact that superhydrophobic surface exhibits special wettability,a new concept is developed to realize selective profile control and water shutoff through fabricating superhydrophobic surfaces on the surfaces of pores in formation.In this process,the excellent selectivity of superhydrophobic surfaces to the oil and water is planned to utilize,which could exhibit exceptional repellency towards water and affinity to oil at the same time,so the oil and water are distinguished fundamentally,and then,the oil could permeate through the formation while the water will be stopped.A systematic study composed of optimization of fabrication method,evaluation of practicability,research of selective profile control and water shutoff performance,as well as analysis of fabrication and function mechanism was conducted in this project.Firstly,the superhydrophobic surface was fabricated on the core wafer by solution immersion method.Based on the water contact angle on the surface,the fabrication method,formulation concentration and reaction conditions were optimized to accomplish the best fabrication effect,and the adaptability was discussed.After that,the practicability of the superhydrophobic surface including hydrophobicity and stability was evaluated.During the experiment,using the water contact angle of rock in dodecane as a new evaluation index,the temperature tolerance,acid and alkali tolerance,salt tolerance and friction resistance were explored.Furthermore,utilizing core flooding experiment and double-tube parallel experiment,the selective water shutoff and profile control performance were studied.In the experiments,the plugging rate of the core,as well as the profile improvement rate,water cut and oil recovery of the parallel double-tube were attached attention to.At last,the fabrication and function mechanism of superhydrophobic surface were discussed and analyzed.The results demonstrated that,only if using 1.0%Aminopropyltriethoxysilane+0.7%Stearoyl Chlorided+0.2%Triethylamine at 60?,moreover,the pretreatment time and modification time need to be 4 h and 12 h respectively,can we obtain the best superhydrophobic surface,which exhibited the strongest hydrophobicity with water contact angle greater than 157°and rolling angle less than 3°.Moreover,the method was adaptive for sandstone with a high silica content.In addition,it was found that the hydrophobicity would get enhanced in oil,and the superhydrophobic surface had outstanding stabilities covering temperature tolerance,acid and alkali tolerance,salt tolerance and friction resistance by evaluating the practical properties.What's more,through the experimental study of water shutoff performance,it indicated that the superhydrophobic surface could block the water layer effectively without affecting the seepage of oil in cores on the condition that the permeability was lower than 981.8×10^-3?m².In addition,the lower original permeability was,the more powerful water plugging capacity became,and the largest plugging rate was 82.9%.As for the effect of it on profile control,the results showed that the superhydrophobic surface could effectively improve the water absorption profile of the parallel double-tube with permeability max-min ratio up to 12.Consequently,the water cut reduced significantly,while the oil recovery increased by 25%on average.