Synthesis and Evaluation of a Submicron Solid Flocculant GCS
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摘要: 钻井过程中钻井液中亚微米无用固相的含量会越来越高,对钻井液的性能影响很大,因此有必要研发有针对性的絮凝剂以清除钻井液中的亚微米固相。通过室内研究,合成了一种基于壳聚糖的亚微米固相絮凝剂GCS。通过正交实验对合成条件进行了优化,得到最佳壳聚糖浓度为3%,壳聚糖与交联剂质量比为1︰0.28,pH值为7。通过粒度分析、沉降实验,对GCS的絮凝效果进行了评价,并采用红外光谱、Zeta电位、扫描电镜等方法分析了其絮凝机理。实验结果表明,GCS絮凝效果显著,对亚微米高岭土的絮凝率在95%以上,与聚丙烯酰胺类絮凝剂相比,不增黏,絮体粒径集中且易分离;在碱性条件下,GCS具有更好的絮凝效果,随着pH值和GCS加量增大,絮凝效果增强,絮体更加稳固;GCS可通过-OH、-NH以及-C—N、-NH2等官能团与高岭土颗粒发生强吸附作用,并与颗粒表面发生电中和作用,使高岭土颗粒电位升高、聚结沉降,达到高效絮凝作用。Abstract: Submicron solids laden in drilling fluid as drilling proceeds greatly affect the properties of the drilling fluid, and are thus needed to be removed with flocculants dedicated for the submicron solids. GCS is such a flocculant synthesized with chitosan. The optimum synthetic conditions determined through orthogonal experiment were as follows:3% chitosan, mass ratio of chitosan and crosslinking agent=1:0.28, pH=7. Particle size analysis and sedimentation test were done to evaluate the flocculating effect of GCS, and the flocculating mechanisms of GCS were determined through IR spectroscopy, zeta potential measurement and SEM. It has been found that GCS has good flocculating ability, 95% of submicron kaolinite particles can be flocculated. Compared with other flocculants, such as polyacrylamide, GCS does not viscosify drilling fluids; the sizes of the flocs are narrowly distributed and are thus easy to be separated from drilling fluid. GCS has better flocculating effect in alkaline environment. At higher pH value and GCS concentrations, better flocculation can be achieved, and the flocs become more compact. GCS has -OH, -NH, -C═N and -NH2 functional groups with which GCS is tightly adsorbed onto the surface of kaolinite particles through these groups, neutralizing the electric charges on the surface of the kaolinite surface, hence increasing the potential of kaolinite particles, thereby coalescing the particles to form flocs.
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Key words:
- Flocculant /
- Submicron /
- Solids /
- Water base drilling fluid
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