关键词: 油基钻井液, 高温, 高压, 流变性, 表观粘度, 预测模型

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