新型改性羟丙基瓜胶及其在超高温压裂液中的应用

为提高稠化剂的抗温性，以羟丙基瓜胶、2-吡咯烷酮和（2-氯乙基）三甲基氯化铵为原料，合成了新型改性羟丙基瓜胶稠化剂。采用TGA进行了抗温性能评价，研究了稠化剂的交联条件以及压裂液的耐温耐剪切性能、破胶性能、残渣含量和岩心伤害评价等。结果表明，羟丙基瓜胶通过引入刚性基团改性后，热降解温度提高到了220℃，在0.6%的加量下增黏效果好。压裂液体系优选配方为:0.6%改性羟丙基瓜胶+0.5%高温防膨剂BZGCY-C-FP+0.5%高温助排剂BZGCYC-ZP+0.1%温度稳定剂BZGCY-Y-WD+0.2%碳酸钠+清水+有机硼锆交联剂BH-GWJL （交联比为100:0.4），在200℃、170 s-1下剪切120 min后黏度保持在60 mPa·s以上，提高了稳定性。现场应用效果表明，该体系能够满足高温井施工要求。 

Application of a New Modified HPG in Ultra-high Temperature Fracturing Fluid

To improve the thermal stability of thickening agent used in fracturing fluid, a new modified hydroxypropyl guar gum (HPG) thickening agent has been synthesized with hydroxypropyl guar gum, 2-pyrrolidone and (2-chloroethyl) trimethyl ammonium chloride. The ability of the thickening agent to resist high temperature was evaluated with TGA, and laboratory study was conducted on the conditions for the thickening agent to crosslink, as well as thermal stability, shearing resistance, gel breaking performance, residue content and core damage of the fracturing fluid formulated with the newly developed thickening agent. It was demonstrated that by introducing a rigid group into the molecular structure, the thermal degradation temperature of HPG was increased to 220℃, and the modified HPG had good thickening performance at a concentration of 0.6% in the fracturing fluid. The optimized formulation of the fracturing fluid is as follows:0.6% modified HPG + 0.5% high temperature swelling inhibitor BZGCY-C-FP + 0.5% high temperature clean-up additive BZGCY-C-ZP + 0.1% high temperature stabilizer BZGCY-Y-WD + 0.2% sodium carbonate + fresh water + organic boron-zirconium crosslinking agent (crosslinking ratio=100︰0.4). After sheared at 200℃ and 170 s-1 for 120 min, the viscosity of the formulation was still higher than 60 mPa·s, indicating that the thermal stability of the fracturing fluid is improved. Field application showed that the new fracturing fluid has satisfied the needs for high temperature operation.