Abstract: The rheological properties of two kinds of oil-based drilling fluids with typical compositions at high temperature and high pressure were measured using the RheoChan 7400 Rheometer.The experimental results indicate that the plastic viscosities and yield points of the drilling fluids decrease with the increase in temperature,and increase with the increase in pressure.The effect of pressure on the apparent viscosity and plastic viscosity is considerable at ambient temperature.However,this effect is reduced gradually with the increase in temperature.The major factor influencing the rheological properties of oil-based drilling fluids is temperature instead of pressure in the deep sections of oil wells.On the basis of numerous experiments,a model for predicting the apparent viscosity of oil-based drilling fluids at high temperature and high pressure was established using the regressive analysis method.It was confirmed that the calculated data were in good agreement with the measured data.The characteristic values of temperature and pressure constant in the model can directly reflect the effects of temperature and pressure on apparent viscosity.The model is convenient for use and suitable for the application in drilling operations.

Key words: oil-based drilling fluids, high temperature, high pressure, rheological property, apparent viscosity, prediction model

摘要： 使用Rheo Chan7400型高温高压旋转粘度计,分别测定了具有典型配方的矿物油钻井液和柴油钻井液在高温高压下的流变性能.实验结果表明,这两类油包水乳化钻井液的表观粘度、塑性粘度和屈服值均随温度的升高而降低,随压力的增加而增大.常温时压力对表观粘度和塑性粘度影响很大,但随着温度升高,压力的作用逐渐减小.在深部井段,影响油包水乳化泥浆流变性的主要因素是温度而不是压力.在大量实验的基础上,运用回归分析方法建立了预测井下高温高压条件下表观粘度的数学模型.经实验验证,计算值与实测值吻合较好.模型中温度和压力的特征值可直观地反映温度和压力对表观粘度的影响程度.该模型应用方便,并适于在生产现场应用.

关键词: 油基钻井液, 高温, 高压, 流变性, 表观粘度, 预测模型