海水矿化度和钙镁离子含量高，配液时会对压裂液溶胀、交联、破胶等造成影响。为降低海水对压裂液的 影响，以甲醛、亚磷酸、多乙烯多胺为原料制备有机膦酸类螯合剂SW-CA，研究了影响其螯合效果的因素，通过 扫描电镜观察晶体形态、分析其作用机理，评价了其对压裂液交联性能和破胶的影响。结果表明，螯合剂 SW-CA对Ca2+、Mg2+ 的螯合值分别为276、218 mg/g，螯合效果随SW-CA用量增大而增大，随矿化度、温度、pH值 增大而减小。加入螯合剂后，沉淀晶体颗粒变得疏松分散，作用机理主要为螯合作用和晶格畸变作用。在海水 中加入1% SW-CA可改善基液的交联性能，提高基液的黏度和耐温耐剪切性。加入1% SW-CA压裂液的破胶时 间可控，破胶性能良好，残渣含量为113 mg/L。将陶粒在加入螯合剂的压裂液破胶液中浸泡4 h后，陶粒表面只 有少量胍胶残渣吸附，避免了无机盐的沉淀析出，降低了对支撑剂导流能力的影响。螯合剂SW-CA与压裂液的 配伍性良好，满足现场施工要求。图13表1参19
When seawater is used to prepare fracturing fluid，its high salinity and high content of calcium and magnesium ions will affect the swelling，crosslinking and gel breaking of fracturing fluid. In order to reduce the influence of seawater on fracturing fluid，the organophosphonic acid chelating agent SW-CA was prepared from formaldehyde，phosphorous acid and polyvinyl polyamine. The influencing factors of the chelation effect were studied. Crystal morphology was observed by scanning electron microscopy. The mechanism of action was analyzed，and the effect of SW-CA on the crosslinking performance and gel breaking of fracturing fluid was further evaluated. The results showed that the chelating value of SW-CA to Ca2+ and Mg2+ was 276 mg/g and 218 mg/g，respectively. The chelating effect increased with the increase of SW-CA dosage，and decreased with the increase of salinity， temperature and pH value. The precipitated crystal particles became loose and dispersed after adding chelating agent. The mechanism of action was mainly chelating and lattice distortion. The addition of 1% chelating agent SW-CA in seawater could improve the cross-linking performance，viscosity，temperature resistance and shear resistance of base fluid. The fracturing fluid adding 1% SW-CA had controllable gel breaking time and good gel breaking performance. The residual content was 113 mg/L. After soaking ceramsite in fracturing fluid gel breaking liquid with chelating agent for 4 h，only a small amount of guanidine gum residue was adsorbed on the surface of ceramsite，which prevented the precipitation of inorganic salts and reduced the influence on the conductivity of proppant. The chelating agent SW-CA had good compatibility with fracturing fluid，meeting the requirements of on-site construction.