CJ2-3型可回收低分子量瓜尔胶压裂液的开发

低分子量瓜尔胶CJ2-3分子链上引入了亲水基团,水溶性好,水溶液30℃[η]值0.842 L/g,按3组K,α求得分子量3.86×105~5.93×105。CJ2-3压裂液以硼酸盐作交联剂,交联剂用量大于常规瓜尔胶类压裂液。0.35%压裂液基液在pH=8.5时黏度仅12 mPa.s,形成的压裂液在热剪切测试中(170 s-1)黏度几乎立即产生,温度达到设定值后黏度保持不变,且60℃、70℃黏度相差不大(在100 mPa.s上下),即该压裂液流变曲线变化平稳,温度敏感性小,易控制,携砂能力强,压裂施工设计难度较小。加入破胶剂(过硫酸铵)可使该压裂液破胶,破胶液黏度符合返排要求。室内模拟破胶实验结果表明,压裂施工完成后,CJ2-3压裂液与低pH值的支撑裂缝表面接触时pH值下降,pH≤8.0时破胶,破胶液黏度接近基液,其中的CJ2-3不发生降解。CJ2-3压裂液滤失控制性能好,滤失量小,滤饼可在地层中自行破胶,易清除。长庆油田的3口油井用CJ2-3压裂液压裂,未加破胶剂的1口井,压裂液返排率达92.9%,返排压裂液在30℃放置7天,黏度下降30.8%。返排压裂液中补加各种添加剂得到的回收压裂液,流变性和其他性能与原始压裂液一致。图5表8参4。     

Structure—activity correlations for sulphur EP additives

A series of new sulphur compounds was synthesised. Mercaptoheterocycles and mercaptoethanol were reacted with C₁₂-C₂₂ chloroacetates. Mercaptoethanol derivatives were subsequently reacted with trialkyl borates. The solubility of S-methylcarbalcoxy derivatives in both mineral oil and synthetic esters strongly depended on the alkyl group length, the most soluble being the C₁₂. C₁₄ derivatives. Three tests were used to estimate the antiwear (AW) and extreme pressure (EP) performance of the sulphur compounds: a four ball machine, an LFW-I machine, and a Falex tester. Despite some differences resulting from the test methods, the best EP characteristics were obtained with the 2-mercaptobenzothiazole derivatives. This showed that even a strongly bonded sulphur atom, such as that of the thiazolic ring, participates in surface layer formation. Mercaptoethanol derivatives were less soluble in either mineral or ester-based synthetic oils. Esterification of the hydroxyl groups with trialkyl borate improved their solubility and load carrying performance.     

Effect of molecular structure of organic borates on their friction and wear properties

Six organic borates of different molecular chain length were synthesised, and the friction and wear properties of these borates as oil additives were evaluated using a Timken Tester. X-ray photoelectron Spectroscopy (XPS) was used to study the surface composition and valence state of boron on the rubbed surfaces. It was found that the antiwear and friction reduction effects of the borates are significantly influenced by the molecular chain length. The longer the chain length, the lower the friction coefficient and wear, and the higher the failure load. XPS analyses of rubbed surfaces revealed that the binding energy of B_IS increased after rubbing, but no pure B(OH)₃ and B₂O₃ was generated. the load-carrying capacity and the antiwear effect are probably related to the ratio of numbers of carbon atoms to numbers of boron atoms on the rubbed surfaces.