Robertson-Stiff流体在偏心环空中的流动

石油钻井和完井过程中,经常出现泥浆、水泥浆和完井液在偏心环空中的流动。Robertson-Stif流体在描述这些流体的流变性时有很高的精度。文中根据Robertson-Stif流体的流变方程和偏心环空环隙间距的几何关系,利用相似原理,求解了该流体在偏心环形空间中作层流轴向流动时适于工程应用的二元速度分布,以及平均流速、流量和压降的表达式。研究表明:液体在偏心环形空间流动时与在同心环空中流动的最大差异,在于流经偏心环空不同间隙处流速的较大差异。文中还把Robertson-Stif流体的计算结果与采用宾汉模式和幂律模式的计算结果进行了对比。

Flow of Robertson_Stiff Fluids Through an Eccentric Annulus

Flow of drilling fluids, cement slurries and completion fluids through an eccentric annulus is an everyday event in petroleum drilling and completing enginering. While Robertson_Stiff (RS) rheological model on the basis of its proven success for describing various non_Newtonian fluids is more accurate than over other rheological models. In this paper, based on the RS fluid rheological equation and the geometrical relationship of eccentric annular clearance with other parameters, the axial_flow velociyt distribution, the annular average velocity,the volumtrical flow rate and the frictional pressure drop are worked out as RS fluid flowing through an eccentric annulus where purely laminar flow is assumed. Results show that the main difference between concentric annular flow and eccentric annular flow lies in that the velocity profile is substantially altered in the annulus when the innner pipe is no longer concentric and the velocity in the reduced region of eccentric annulus is much smaller than that of the increased region. Moreover, the paper also compares the computed results by the use of RS model with that of Bingham model and Power_Law model.