四氧化三锰水基钻井液润滑性能评价与研究

Research on the Lubricity of Drilling Fluid Weighted with Mn_3O_4

采用Zeta电位分析仪、激光粒度仪、扫描电镜测定了四氧化三锰、重晶石、铁矿粉的表面电荷、粒度分布和微观形状,对比考察了3种加重剂加重的水基钻井液的极压润滑系数和泥饼黏滞系数。实验结果表明,3种加重剂中,四氧化三锰颗粒的表面电荷最高,在钻井液中的表面亲水性最强,其颗粒呈球形,粒度分布窄、粒径小、比表面积大,颗粒的稳定性最强;因此四氧化三锰加重钻井液的极压润滑系数和泥饼黏滞系数最小;四氧化三锰、重晶石、铁矿粉加重钻井液泥饼润滑性改善的临界密度分别为1.3、1.5和1.5 g/cm3;重晶石、铁矿粉与四氧化三锰复配能改善他们加重钻井液的极压润滑性能及泥饼的润滑性能。分析其机理为四氧化三锰高的表面电荷使得颗粒分散均匀,降低了钻井液流动的内摩擦力,合理的粒度分布能增加起轴承效应的粒子数量,球形颗粒能显著降低钻井液固相颗粒之间的摩擦力。

Water base drilling fluids weighted with trimanganesetetraoxide have widely been used in drilling HTHP well,high angle well and extended-reach well because of their good lubricity.Three weighting agents,trimanganesetetraoxide,barite and hematite were analyzed in laboratory with Zeta-potentiometer,laser particle size analyzer and SEM for their surface charge,particle size distribution and microscopic shape,and water base drilling fluids weighted with these materials were investigated.Experimental results show that water base drilling fluids weighted with trimanganese tetra oxide have the lowest coefficient of friction measured with extreme pressure tester,and the lowest coefficient of viscosity of mud cake.The critical densities of water base drilling fluids at which the mud lubricity is improved are 1.3 g/cm^3,1.5 g/cm^3 and 1.5 g/cm^3 for trimanganesetetraoxide,barite and hematite,respectively.Drilling fluids weighted with barite or hematite will have their lubricity obviously improved if trimanganesetetraoxide is further added therein.