pH值和稀释剂对固井前甲酸盐钻井液性能的影响

Effect of pH Value and Diluent on the Performance of Formate Drilling Fluid before Cementing

固井前甲酸盐钻井液的流变性和失水造壁性差是导致固井质量不理想的关键问题之一。为提高环空钻井液顶替效率和井壁泥饼冲洗效率,研究了pH值和稀释剂磺化丹宁对油田现场某井区甲酸盐钻井液流变性和失水造壁性的影响,通过比较甲酸盐钻井液调节前后形成泥饼的微观结构,分析了钻井液性能改变的机理。结果表明,pH值和稀释剂对甲酸盐钻井液的流变性和失水造壁性的影响较大。随pH值和稀释剂加量的增大,甲酸盐钻井液的塑性黏度、动切力、高温高压滤失量和泥饼厚度先降低后增加,泥饼冲洗效率和界面胶结强度先增加后降低。在90℃下,现场甲酸盐钻井液适宜的pH值为11.5、稀释剂最佳加量为0.3%。甲酸盐钻井液经NaOH溶液和稀释剂调节后,改善了黏土颗粒的分散性,优化了钻井液性能,并提高了形成泥饼的致密性,有利于环空钻井液的顶替和井壁泥饼的冲洗清除,改善固井胶结质量。

The inferior rheological and filtration properties of formate drilling fluid was the key question to caused unsatisfactory cementing quality. In order to improve the efficiency of annulus drilling fluid displacement and mud cake flushing,the effects of pH value and diluent sulfonated tannin on rheological properties and water loss of formate drilling fluid in a well area of oilfield were studied,the microstructures of formate drilling fluid mud cake formed by before and after adjustment were compared,and the change mechanism of drilling fluid property was analyzed. The results showed that pH value and diluent had a great influence on the rheology and water loss of formate drilling fluid. As the pH value and the addition of diluent increased,the plastic viscosity, dynamic shear force,HTHP filtration and mud cake thickness of formate drilling fluid decreased first and then increased,while the washing efficiency and interfacial bonding strength increased first and then decreased. At 90℃,the suitable pH value of formate drilling fluid on the scene was 11.5,and the best dosage of diluent was 0.3%. The dispersion of clay particles,the performance of drilling fluid,and the compactness of mud cake formation were improved after formate drilling fluid was adjusted by NaOH and diluent. It facilitated the displacement of annulus drilling fluid and the flushing and removal of mud cake on the borehole wall,and improved the cementing quality.