关键词: 油基钻井液, 高温高压, 流变模式, 流变参数, 预测模型

Abstract: For the deep wells with high temperature and high pressure,the drilling fluids are often affected by temperature and pressure.The careful investigation on the rheological properties of oil-based drilling fluids at high temperature and high pressure is very important for precisely calculating the pressure drop in annular and predicting the equivalent circulation density as well as controlling the bottomhole pressure.The rheological properties of oil-based drilling fluids with typically compositions at high temperature and high pressure indicated that the effect of pressure on the apparent viscosity,plastic viscosity and dynamic shear force at ambient temperature was considerable.However,this effect could be gradually reduced with the increase of temperature.Temperature is the major factor influencing the rheological properties of oil-based drilling fluids.The mathematical model for predicting the apparent viscosity,plastic viscosity and dynamic shear force of oil-based drilling fluids at high temperature and high pressure was established using the regressive analysis method.The calculated data with the model are in good agreement with the measured data,the correlation coefficients are more than 0.98.The model can be used to accurately predict the rheological parameters and calculate the hydraulic parameters in the deep sections of oil wells during drilling operation.

Key words: oil-based drilling fluids, high-temperature and high-pressure, rheological model, rheological parameter, prediction model