In the drilling process of horizontal well,poor hole cleaning can lead to downhole complexities such as increase in friction torque of drilling tools,sticking and sharp increase in annulus pressure,which seriously restricts the horizontal well extension ability. In previous studies,the important effect of drill pipe rotation speed on wellbore cleaning is often ignored,and the influence of drill pipe rotation on annulus flow field is also not considered in the established models. In order to explore the comprehensive effect of drill pipe rotation speed and displacement on cuttings migration,this study first established a calculation model of cuttings bed thickness in horizontal wells considering the condition of drill pipe rotation after calculating the eccentric annulus flow field when the drill pipe rotates in horizontal wells and analyzing the three-dimensional stress of cuttings particles. In the process of horizontal section drilling,due to gravity,the drill pipe sinks at the lower edge of the annulus,forming a narrow annulus area. The model calculation results show that the axial flow rate of the drilling fluid in this area is slow, which is often not enough to reach the critical flow rate of rock cuttings startup,resulting in cuttings deposition. At this time,the circumferential velocity of the drilling fluid caused by the rotation of the drill pipe can bring the cuttings into the high-speed basin at the upper edge of the annulus,thus achieving the effect of efficient rock carrying. Then,the model is used to calculate the seven kinds of annulus sizes commonly used in the field,and the drill pipe rotation speed under different hole sizes is recommended. Finally,the model is used to compare and analyze the actual drilling situation in Mahu Lake,which verifies the reliability of the model and also proves that the model has a certain guiding role in engineering practice.
2023, 46 (2):
8-14.