带屈服值的假塑性流体同心环空稳态波动压力研究

Study on Steady Surge Pressure for Yield-Pseudoplastic Fluid in a Concentric Annulus

管柱在充满钻井液的井眼内运动时所产生的波动压力是影响井眼稳定的主要因素．其大小是制定泥浆附加密度的主要依据．因此要求对实际波动压力的预测有较高的精度，而其精度与泥浆流变模式的选择密切相关．屈服假塑性流体属于三参数模式，因其精度高，近年来国外多用其描述钻井液的流变性．文中以该模式为基础，从理论上推导了定向井同心环空中起下钻或下套管过程中，稳定层流条件下钻井液粘性产生的波动压力计算模式．为便于现场应用，绘制了不同情况下波动压力系数的变化规律．并给出了计算示例．对准确预测钻并作业过程中波动压力的大小、控制起下钻速度提供了理论依据．

Surge pressure causcd by Pipe moving througlithe wellbore full of drilling fluid is the main factor affecting wellbore stability, on which the additional mud density is designed Thus it is desired to predict the surge pressure with high accuracy.While this is closed related with the selection of mud rheological models.Yield-Psoudoplastic model which has three parameters and is famous for its higher acccuracyhas been used to describe the mud rheo logical properties in recent years Based on this model the paper presnets a new theortical model for calculating surge pressure caused by mud viscosity during trippingor casing in a concentric annulus of directional wells under steady laminar situation.For convenience,the paper plots the distribution of the co efficients of surgepressure for different conditions.An example is given.These results provide the basis for controlling pressure surges and tripping velocity