新型壳聚糖-邻苯二酚化学固壁剂合成与性能评价

泥页岩地层井壁不稳定是物理因素和化学因素共同作用的结果,基于多元协同井壁稳定理论,加强物理封堵和化学胶结是钻井液稳定井壁作用的重要技术措施。笔者以壳聚糖、含有邻苯二酚结构的聚合物为单体,采用席夫碱-还原反应方法制备出一种新型化学固壁剂SDGB,并对其性能进行实验研究。实验结果表明,SDGB分子中含有芳环结构和邻苯二酚、胺基等官能团,可与金属离子发生螯合作用,形成稳定的共价键,其相对分子质量约3万。采用搭接抗剪强度测试、页岩滚动分散实验、岩心单轴抗压实验、扫描电镜分析等实验方法评价了其化学固壁特性。结果表明,SDGB具有较好的化学胶结作用,可提高岩样在水中的搭接抗剪强度,增强岩样浸泡后的抗压强度,有效抑制泥页岩水化分散;SDGB可胶结岩样微孔隙、微裂缝中的松散矿物,从而对其进行有效封堵、固结;以化学固壁剂SDGB为关键处理剂,优化出了一套水基钻井液配方,体系在130℃、16 h热滚前后流变性能、滤失性能稳定。 

Synthesis and Evaluation of a New Chemical Borehole Wall Strengthener Made from Chitosan-Catechol

Borehole wall instability in shale formations is a result of combined action of physical factors and chemical factors. An important measure to stabilize shale formations is to plug the formation with physical particles and to reinforce the chemical bonding of the formations. A new borehole wall strengthener SDGB has been developed with chitosan and a polymer having catechol structure through Schiff base reduction reaction. Study on the performance of SDGB showed that SDGB has aromatic ring, catechol and amino group in its molecules, which can react with metal ions through chelation reaction to form stable covalent bonds. The relative molecular weight of SDGB is about 30,000. The performance of SDGB in strengthening borehole wall through chemical action was studied through lap shear strength test, hot rolling test, uniaxial compressive experiment of rock and SEM experiment. It was found that SDGB had good chemical bonding performance which is able to increase the lap shear strength of rock in water, to increase the compressive strength of rocks after soaking, and to inhibit the hydration and dispersion of shales. SDGB can form cementation in the pore throats of a rock and cement the loose minerals inside the micro fractures of a rock, thereby effectively plugging and strengthening the formation. A water base drilling fluid with stable rheology and filtration property before and after aging at 130℃ for 16 hours, was formulated with SDGB as the key additive.