酸性压裂液用有机锆交联剂的合成与性能评价

为构筑与长期CO2驱储层具有更好配伍性的压裂液体系,本文通过正交合成实验,以氧氯化锆、乙二醇、乳酸及氯化铵为原料,成功合成并筛选出可在酸性条件下(pH=1~6)与羧甲基羟丙基胍胶(CMHPG)发生交联反应的有机锆交联剂,系统地评估了有机锆交联CMHPG酸性压裂液体系的成胶时间、成胶强度、流变性能、悬砂和破胶性能、微观结构以及对岩心的损害情况。研究表明:该有机锆交联剂具有优异的延迟交联性能,即使体系pH低至1~2,成胶时间依然可延缓至1~3 min;随着交联剂与聚合物浓度的升高,体系成胶时间缩短,成胶强度增大;在交联剂用量0.03%~0.06%、聚合物用量0.2%~0.7%的范围内,体系黏弹性能可调、成胶时间可控;该体系具有较好的剪切恢复性能,可形成均匀、致密的三维空间网状结构,且在pH为1~3的条件下悬砂性能优异、破胶性能良好。该体系可满足不同地层条件的压裂需要,但应用的温度应不超过145℃。相比于碱性压裂液体系,酸性压裂液体系对岩心的损害性更低。

Synthesis and Evaluation of Organic Zirconium Cross-linker Used in Acidic Fracturing Fluid

In order to develop a fracturing fluid system compatible with the formation treated by long-term CO2 flooding,a novel organic zirconium cross-linker,which could be cross-linked with carboxymethyl hydroxypropyl guar under acidic condition ranging from pH 1 to 6,was synthesized and screened through orthogonal design experiments using zirconium oxychloride,ethylene glycol,lactic acid,and ammonium chloride as main raw materials.The gelation time,gel strength,rheological performance,proppant-settling and gel breaking performance,microstructure and the damage to the fromation of the zirconium-CMHPG crosslinked gel acidic fracturing fluid were systematically evaluated.The results showed that the delay performance of the organic zirconium cross-linker was desirable with the gelation time of 1 to 3 min even at a low pH of 1 to 2.The gelation time shortened and gel strength increased with the increase of polymer and cross-linker concentrations.The gelation time and rheological performance of the gel system could be optimized to meet the specific fracturing operations at the polymer concentration of 0.2%—0.7%and the cross-linker concentration of 0.03%—0.06%.The gel system had a desirable shear recovery performance,a uniform and compact 3D network structure was generated within the gel,and the proppant-settling and gel breaking performance were satisfied at the pH of 1—3.The gel system could be applied in the reservoir with formation temperature of less than 145℃.the low pH fracturing fluid system produced a better return permeability than the high pH system.The damage of the acidic fracturing fluid to the formation was lower than that of the alkaline fracturing fluid.