注水泥流体密度与流变参数匹配的计算方法

摘要

为提高注水泥时的顶替效率,对注水泥流体(钻井液、前置液和水泥浆)之间的密度匹配、流变性能匹配进行设计很重要,但目前缺乏该方面的理论设计方法.针对直井、注水泥流体均为幂律流体、层流、套管居中等条件下的注水泥顶替过程,在对两流体相互顶替的受力分析的基础上,建立了使顶替流体与被顶替流体在横截面上以同一平均流速进行顶替流动(即同步上返)时的两流体密度和流变参数匹配要求的定量计算方法及公式,所建立的公式可以应用于注水泥设计.分析所建立的公式表明,当顶替流体密度大于被顶替流体密度、顶替流体的流性指数大于被顶替流体的流性指数、顶替流体的稠度系数大于被顶替流体的稠度系数时,可提高顶替效率.%In order to increase the displacement efficiency,it is important to design and match the density and rheological parameters of the cementing fluids (drilling fluid,pad fluid and cement slurry), while the theoretical design method is not available at present. A vertical well fluid displacing is analyzed assuming power-law fluid with laminar flow during the cementing displacement process. On the basis of this analysis,a method and formula was established to calculate the fluid density and rheological parameters by which the displacing and displaced fluids have same velocity in flow of replacement. The formula can be applied in cementing design. The analyses show that when fluid density in displacing fluid is higher then displaced fluid,then the flow index and viscosity index of displacing fluid is higher than displaced fluid,and the displacement efficiency is increased.