深水高温高压井钻井液当量循环密度预测模型及应用

Prediction Model of Equivalent Circulating Density of Drilling Fluid in Deep HPHT Wells and Its Application

深水高温高压井具有井筒温度场变化复杂、钻井液物性变化大等特点,导致钻井液当量循环密度(ECD)难以准确预测。为此,根据南海某研究区深水高温高压井钻井资料,通过PVT测量仪和旋转黏度计研究了深水水基钻井液当量静态密度、流变参数与温度、压力之间的响应特征,并根据实验数据拟合经验模型参数,同时考虑温度和压力对钻井液物性参数的影响、海底增压对井筒流场与温度场的影响,对深水高温高压井ECD计算模型进行完善。研究表明:高温高压环境对水基钻井液物性有较大影响,海底增压泵排量越高,井筒内ECD越高。利用模型对南海ST362-1d井进行实例计算,ECD模型预测值与实测值平均误差仅为0.249%。该研究结果对深水高温高压井水力参数优化设计及井筒压力控制具有一定的参考价值。

Deep HPHT wells have the characteristics of complex wellbore temperature field changes and large changes in the physical properties of drilling fluids,multiplying the difficulties in accurate prediction of the equivalent circulating density(ECD)of drilling fluid.To this end,based on the drilling data of deep HPHT wells in a study area in the South China Sea,the characteristics of response between the equivalent static density and rheological parameters of deep water-based drilling fluids and the temperature and pressure were investigated by means of PVT meter and rotary viscometer.The parameters of empirical model were fitted based on experimental data,while the ECD calculation model of deep HPHT wells was improved with consideration of the influence of temperature and pressure on the physical parameters of drilling fluid and the influence of subsea pressurization on the flow field and temperature field of wellbore.The study showed that,the physical properties of the water-based drilling fluid were greatly affected by high temperature and pressure,and the higher the displacement of the subsea booster pump,the higher the ECD in the wellbore.The model was used in the calculation of Well ST362-1d well in the South China Sea,and the average error was only 0.249%between the predicted value of ECD model and the measured value.The results of the study can serve as references for the optimal design of hydraulic parameters and wellbore pressure control in deep HPHT wells.