欠平衡钻水平井全井段气液两相流模型研究

为了给欠平衡钻水平井技术提供工程设计依据，根据气液两相流研究方法在欠平衡钻井中的应用评价结果，利用环空及圆管内的气液两相流力学研究成果，建立了欠平衡钻水平井全井段气液两相流模型，用数值求解方法求解了该模型，并通过现场测量数据和试验数据验证了该模型的预测结果。该欠平衡钻井模型能模拟欠平衡钻水平井的全过程，预测欠平衡钻井过程中井底压力变化规律，对欠平衡钻井环空及钻柱内压力的预测精度在5%左右，能够满足欠平衡钻井工程设计的要求。该模型为欠平衡钻井井底压力预测及控制提供了理论依据，保证了欠平衡钻井的成功实施。

Model research of full hole two-phase flow in underbalanced horizontal well drilling

In order to provide engineering design considerations for the UBD horizontal well technique, according to the evaluation on the application of the two-phase flow research method to the UBD drilling, using the mechanical research results of two-phase flow in annulus lines, a full hole two-phase flow model is established. The numerical method is used to find the solution to the model. The predicting results of the model are verified using the field measurement data and experimental data. The model can be used to simulate the whole process of the UBD horizontal well drilling and predict the bottomhole pressure variation rule. It is shown that the accuracy of the model is about 5% in predicting the casing pressure and the pressure in string, and it can meet the requirement of the engineering design of UBD drilling. The two-phase flow model provides theoretical basis for the prediction and control of the borehole pressure and guarantee the successful operation of UBD drilling.