Preparation And Evaluation Of High Temperature Resistant Acid Gel Fracturing Fluid System

Acid gel had been widely used in proppant-carrying acid fracturing technology.While the viscosity of acid gel reduced sharply in high temperature reservoir,it cannot meet the demand of high-temperature carbonate reservoir reform.A novel high-temperature resistant polymer was synthetized,and new high-temperature resistant acid gel was prepared in this paper.The property of this fracturing fluid had also been evaluated.The reaction mechanism of polymer thickener and crosslinking agent had also been investigated in this paper.A novel amphoteric terpolymer which based on AM,SSS,and DAC was synthetized,the effects of reaction conditions have also been studied.After the posthydrolysis process,the copolymer reacted with high-temperature resistant crosslinking agent,and a new crosslinking system was formed.Some additives,including corrosion inhibitor and ferric ion stabilizer,have also been studied.Then,complete fracturing fluid formula was formed.The shear viscosity of acid gel could be settled in 60 mPa·s at 120?.This system has perfect sand carrying capacity and acid-rock reaction rate reducing ability,these properties are conducive to the formation of long fractures.After the shear test at 170 s^-1,510 s^-1,170 s^-1 for every 3 minutes,the viscosity could restore to 60%of initial viscosity.The corrosion inhibition test showed that this fracturing fluid had perfect corrosion inhibition ability.The viscosity of gel-breaking fluid was lower than 10 mPa·s,and there was no residue in gel-breaking fluid,so this fracturing fluid had excellent gel breaking property.The test of rheological properties showed that the acid gel was pseudoplastic fluid,and the relation between shear rate and viscosity was fit well with Ostwald-dewo power law equation.The crosslinking reaction mechanism of fracturing fluid had also been investigated by rheological properties test and electron microscope experiment.The effects of temperature and shear rate on crosslinking reaction were studied.The rheological dynamic equation of crosslinking reaction had also been established,and the equation was fit very well with experiment data.The fracturing fluid had tight spatial network microstructure in electron microscope experiment,which was greatly different from polymer based liquid.