耐高温可加重酸性交联压裂液的研发与性能评价

Development and performance evaluation of high-temperature resistant and acidic-crosslinking weighted fracturing fluid

针对高温深层油气藏埋藏深,地层破裂压力高、压裂施工难度大的问题,开展耐高温可加重压裂液研究。通过室内实验自主合成了一种耐温抗盐的聚合物稠化剂TS-700和适用于酸性交联的有机锆交联剂OZ-60,优化了添加剂加量,形成了一种耐温180℃可加重酸性交联压裂液体系。研究了加重压裂液黏度、减阻、延迟交联规律,并评价了耐温抗剪切性能、悬砂性能、破胶及岩心伤害性能和管柱腐蚀能力。结果表明,该体系在酸性条件下进行交联,通过调整交联剂加量和pH,交联时间可控在3~12 min;高温有利于黏度提升,加重降低了基液黏度,密度为1.20 g/cm^(3)的加重压裂液配方在180℃条件下剪切120 min后,保留黏度仍大于70 mPa·s。加重剂会在一定程度上降低压裂液的减阻性能,但在不同稠化剂加量下的加重压裂液减阻率仍可达68.04%以上,满足有效降低长距离井筒中摩阻损失的要求。交联压裂液在常温和100℃条件下均展现出优异的悬砂效果,支撑剂沉降速率低。破胶与岩心伤害实验结果表明,交联体系在0.03%破胶剂加量下即可实现完全破胶,破胶液对致密岩心伤害率仅为19.42%。高温高压动态腐蚀实验结果表明,全配方压裂液对N80和13Cr钢材具有较低的腐蚀速率,能够保障现场压裂管柱的安全性。

Aiming at the problems of deep burial,high formation pressure and difficult fracturing stimulation of high-temperature deep oil and gas reservoirs,research on high-temperature resistant weighted fracturing fluid was carried out.A polymer thickener TS-700,which is resistant to high temperature and salt,and organozirconium crosslinker OZ-60,which is suitable for acid crosslinking,were independently synthesized in the laboratory,and the additive dosage was optimized to form an acidic-crosslinking fluid system with a temperature resistance of 180℃.The viscosity,drag reduction and delayed crosslinking of the weighted fracturing fluid were studied,and the temperature and shear resistance,sand carrying,gel-breaking,core damage and string corrosion ability were systematically evaluated.The experimental results show that the novel fluid system can be crosslinked under acidic conditions,and the crosslinking time can be controlled within 3~12 min by adjusting the dosage of crosslinker and the pH value.High temperature is conducive to the improvement of viscosity,while the addition of salt will reduce the viscosity of the base fluid.The retention viscosity of the weighted fracturing fluid formula with a density of 1.20 g/cm^(3) is still greater than 70 mPa·s after shearing for 120 min at 180℃.Weighting agent can reduce the drag reduction performance of fracturing fluid to a certain extent,but under different thickener dosages,the drag reduction rate of the weighted fracturing fluid can still reach more than 68%,which meets the requirement of effectively reducing the friction loss in long wellbores.The crosslinked fracturing fluid showed excellent sand suspension at room temperature and 100℃,with low proppant settling rate.The results of gel-breaking and core damage show that the crosslinked system can achieve complete gel breaking at 0.03%of the dosage of breaker,and the damage rate of gel-breaking liquid to the tight core is only 19.4%.The high-temperature and high-pressure dynamic corrosion test results show that the fully formulated fracturing fluid has a low corrosion rate on N80 and 13Cr steel,which can ensure the safety of the fracturing string in the field.