| In order to meet the demands of high temperature and deep reservoir exploitation,an organic zirconium crosslinking agent,with the maxium heat resistance of 198? and the crosslinking time of 12 to 17 minutes,named KST-5 was synthesized.The optimal process condition of organic zirconium with temperature-resistance property was obtained by investigating the effects of types and content of ligands on crosslinking performance of butyl zirconium as main material,acetylacetone,triethanolamine and polyol complex TN-1 as ligands,methanol and water as solvent.It showed that optimal dosage and the best synthesis process was that butyl zirconium was 13%,the weight ratio of butyl zirconium to acetylacetone is 1:1,the weight ratio of butyl zirconium to triethanolamine was 1:1.75 to 1:2,the weight ratio of butyl zirconium to poly-alcohol complex TN-1 was 1:2.5 to 1:2.75,the weight ratio of methanol to water is 1:0.25 to 1:0.5,the optimal reaction temperature was 85 to 90? and the reaction time was 4 to 5 hours.The crosslinking agent has the good stability,it can be mixed with water at any ratio and be placed more than 5 months without stratification.The typically character of crosslinker is not slinks at room temperature but crosslinks at high temperatures.When Na2CO3 was used to adjust the pH value,the crosslinked gel had the best viscoelasticity.Moreover,the results showed that the gel is good or bad directly related to the content of the base,the temperature and the crosslinking ratio.The formulation of the high temperature crosslinked fracturing fluid was obtained by optimizing the various additives of the fracturing fluid:the dosage of fungicide 1227 is 0.1%,the dosage of temperature stabilizer B-13 is 0.4%,the dosage of clay stabilizer KCl is 1%,the dosage of clean up additive C-56 is 0.4%and the dosage of pH adjuster Na2C03 is 0.1 to 0.15%.The amount of HPG and KST-5 is in the range of 0.5 to 0.75%and 0.8 to 1.2%.The viscoelasticity of high temperature fracturing fluid showed that the elasticity of the system was larger than that of viscous,and the viscoelasticity was enhanced with the increase of the amount of thickener and crosslinker.What's more,the results indicated that the temperature resistance of fracturing fluid is related to the concentration of thickener,crosslinking ratio,pH and type of crosslinking agent,etc.Compared with organic zirconium crosslinker TCL-2 and KST-5,which has better delay performance and temperature resistance than TCL-2.When the temperature is up to 198 ? and the shearing rate and constant shearing time of the fracturing fluid are 170s-1 and 120min,the viscosity can still be maintained about 65mPa-s,at the same time,the crosslinking time can reach 14min.By measuring the rheological parameters,the results show that the value of n is always less than 1,and the value of K decreases with the increasing of temperature and the dosage of the thickening agent and crosslinke.In addition,the experimental results also showed that 30%of the ceramic particles does not settle at 90 ? temperature and stilling for 12 hours.When the temperature reaches up to 180?,the fracturing fluid filtration coefficient is 1.13×10-5 m/min1/2.Controlled the the dosage of ammonium at 0.05%,it could be insured the fracturing fluid system completely broken in 2 hours under the condition of 150 ? above.When the HPG content is 0.7%,the residue of the breaking fluid is 276 mg/L.Furthermore,the breaker can be compatible well with the formation water and stratum crude oil. |
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