纳米增强硅氧烷类超临界二氧化碳增稠剂的制备及性能评价OA

Supercritical carbon dioxide(SC-CO₂)anhydrous fracturing technology is considered suitable for shale oil and gas development;however,its low viscosity causes issues such as gravity overlay,viscous fingering and poor sand-carrying capacity,which limit the application of SC-CO₂ in fracturing operations.In this paper,a fluoro-and amino-modified siloxane polymer(FND)was synthesized via ring-opening condensation polymerization using trifluoropropyl cyclotrisiloxane(F),γ-aminopropylmethyl diethoxysilane(N)and octamethyl cyclotetrasiloxane(D)as the main raw materials.The polymer was grafted onto the surface of γ-methacryloxypropyltrimethoxysilane-modified nanosilica(NPs)via a Michael reaction to obtain NPs-FND,which was then used as a thickener for SC-CO2.The dissolution and thickening effects of NPs-FND in SC-CO2 were tested using a high-temperature and high-pressure visual dissolution kettle.The results showed that the dissolution pressure of NPs-FND in SC-CO2 gradually decreases with increasing N component content.However,beyond 40%,the pressure reduction slowed and the system's viscosity decreased marginally.At 313.12K,3%0.4F0.1N0.5D(corresponding to the optimal molar ratio of F,N and D is 0.4∶0.1∶0.5)reduced the system pressure to 21.3MPa with a measured viscosity of 1.74mPa·s.As the content of NPs-0.4F0.1N0.5D in SC-CO2 increased,the viscosity of the system enhanced.NPs∶0.4F0.1N0.5D had an optimal mass ratio of 1∶9.With 4%NPs-0.4F0.1N0.5D,the viscosity of SC-CO2 increased to 3.61mPa·s,while the dissolution pressure rose by only 0.2MPa compared to 0.4F0.1N0.5D.Meanwhile,low NPs content(2.5%—7.5%)in NPs-0.4F0.1N0.5D reduced its dissolution pressure in SC-CO ₂,while high NPs content(10.0%—12.5%)slightly increased the dissolution pressure but remained below 26MPa.Experiments demonstrated that siloxane-based polymer grafted NPs exhibited excellent dispersibility in SC-CO₂,significant thickening effects and the capability to reduce dissolution pressure.