Research On Adaptability Of Fracturing Fluids To FuDong Ultra Low Permeability Reservoir

As the working liquid in fracturing operation, fracturing fluid plays the role of transferring pressure, forming fracture and bringing proppants into the fracture. Therefore, the adaptability of fracturing fluid to formation is the important factors of influencing formation fracturing construction and the effect of increasing production after fracturing operation. Aiming at this question, the adaptability of some fracturing fluids used commonly to FuDong ultra-low permeability reservoir is evaluated in this paper.Firstly the system performance of guanidine gum fracturing fluid, hydrophobic associating polymer fracturing fluid, clean fracturing fluid, emulsion fracturing fluid and foam fracturing fluid is evaluated, the results shows that:(1) the anti-clay swelling agent used in these fracturing fluids have good anti-swelling performance;(2) both guanidine gum fracturing fluid and emulsion fracturing fluid have higher residue content; clean fracturing fluid shows the performance of whole filtration, but emulsion fracturing fluid and foam fracturing fluid have the smallest filtration coefficient; the surfactants used in clean fracturing fluid and emulsion fracturing fluid will lead to emulsification between form formation oil and water, but the 1831 of different concentrations have different effect on core wettability; for foam fracturing fluid, it takes longer time to make the gel broken.The results of fracturing fluids static filtration show that: the guanidine gum fracturing fluid, hydrophobic associating polymer fracturing fluid, emulsified fracturing fluid and foam fracturing fluid have the damage less than 10% to core matrix permeability. However, because of the emulsification between form formation oil and water, clean fracturing fluid will lead to the damage of 36.4% to the core matrix permeability. The results of fracturing fluids dynamic filtration evaluation show that: how big the damage is depends not only on fracturing fluid type but also whether the filter cake will be formed and the permeability of cores. Guanidine gum fracturing fluid, hydrophobic associating polymer fracturing fluid, emulsified fracturing fluid and foam fracturing fluid has the damage less than 10% to the cores with permeability of 0.1×10-3μm2~1×10-3μm2 in the process of the dynamic filtration; when the core permeability is about 10×10-3μm2, guanidine gum fracturing fluid and hydrophobic associating polymer fracturing fluid will respectively cause damage of about 30% and 40%, and there will be some filter cake formed on the end of the cores; when the core permeability is about 50×10-3μm2, there will be no filter cake and almost no damage in the process of guanidine gum fracturing fluid dynamic filtration. But to the core with the same permeability, hydrophobic associating polymer fracturing fluid will cause damage as high as 54.5% with filter cake formed on the end of the core.Sand pack test showed that: when fracturing fluid is broken and flow back, the bigger the residue content is, the bigger the damage of fracturing fluids to fracture conductivity is. However, if the fracturing fluids failed to be broken completely, the damage of fracturing fluids to fracture conductivity do not depends on the residue content but the amount of residual gum. The more the amount of residual gum is, the bigger the damage is.