A modified guar gum (CTGG) has been prepared to minimize formation damage caused by conventional guar gum fracturing fluids.CTGG was obtained through solvent method using guar gum as the raw material,CT1 (a long chain hydrophobic cationic monomer produced with N,N-Dimethyl dodecyl amine and epichlorohydrin) as etherizing agent,methanol as solvent,and sodium hydroxide as catalyst.Characterization of CTGG with IR spectroscopy showed that hydrophobic cationic group has been introduced into the molecular structure of CTGG which dissolved in 60 min.Water insoluble matters and residue were both less than conventional guar gum,The viscosity of CTGG is greater than GG and HPG at different concentrations.Other evaluation experiments indicated that gels formed by CTGG in water had viscosity of 300 mPa · s at 120 ℃.A fracturing fluid containing 0.35％ CTGG (mass ratio) was resistant to shearing at 120 ℃,having viscosity of at least 67.4 mPa · s and residue of only 246.45 mg/L.These data demonstrate that CTGG has good solubility,thickening performance and temperature and shearing resistance,which are beneficial to protect reservoirs from being damaged.%为解决瓜胶压裂液的高地层伤害等问题,对瓜胶GG进行了改性.用十二烷基二甲基叔胺与环氧氯丙烷合成了长链的疏水阳离子单体CT1,以瓜胶为原料,疏水阳离子单体CT1为醚化剂,甲醇为溶剂,氢氧化钠为催化剂,通过溶剂法制备了改性瓜胶CTGG.对其结构进行了红外光谱分析,评价了其溶解性能、增稠性能、水不溶物含量、残渣含量和耐温耐剪切性能.结果表明,CTGG中成功引入了疏水阳离子基团,可以在60 min内基本溶解,其水不溶物含量和残渣含量均低于瓜胶,残渣含量仅为246.45 mg/L;不同浓度下,CTGG的基液黏度均大于GG和HPG;所形成的冻胶在120℃条件下,质量分数为0.35％的CTGG所配成的压裂液体系在120 ℃下依然具有良好的抗剪切性能,黏度能够维持在67.4 mPa·s以上;质量分数为0.40％时,冻胶的黏度能稳定在300 mPa·s.因此,CTGG具有良好的溶解性能和增稠性能,有利于降低对储层导流能力的伤害,且耐温耐剪切性能好.
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