幂律流体偏心环空流动中钻井液粘附系数研究

为了研究偏心环空中钻井液的粘附系数,建立了幂律流体偏心环空理论模型,用有限元软件Fluent对所建模型进行了模拟计算,分析了在环空紊流模型下钻井液粘附系数与套管运动速度及偏心距之间的关系,并对比分析了钻井液粘附系数和波动压力随偏心距的变化趋势。模拟中紊流计算采用κ-ε模型,假设幂律流体做稳定不可压缩流动。分析结果表明,当偏心距从0增大到完全偏心时,钻井液粘附系数减小值大于52%,受套管运动速度的影响较小,可以忽略;钻井液粘附系数和波动压力随偏心距具有相同的变化趋势,随着偏心距的增大,环空中波动压力逐渐减小,且从同心环空到完全偏心波动压力减小了74%。

Research on the Drilling Fluid Adhesion Coefficient in the Eccentric Annular Flow of Power-law Fluid

To study the adhesion coefficient of drilling fluid in eccentric annulus,the theoretical model of power-law fluid in the eccentric annulus was established.The finite element software Fluent was used to conduct a simulation calculation of the model established.The relation between drilling fluid adhesion coefficient,casing motion velocity and eccentricity was analyzed in the annular turbulence model.The variation tendencies of the coefficient and the fluctuation pressure with eccentricity were compared.In simulation,turbulence calculation adopted the κ-ε model,pretending that power-law fluid was in stable incompressible motion.The analysis shows that when eccentricity increases from 0 to complete eccentricity,the coefficient decrease is greater than 52%.The casing motion velocity has slight effect on the decrease and thus it is negligible.The coefficient and the fluctuation pressure with eccentricity have the same variation tendency.With the increase of eccentricity the fluctuation pressure in annulus decreases gradually.The fluctuation pressure decreases by 74% from concentric annulus to complete eccentricity.