钻具屈曲影响下的管柱摩阻扭矩分析

Analysis of Pipe String Friction and Torque Under the Influence of Drilling Tool Buckling

现有摩阻扭矩分析模型,常采用单一的刚杆或软杆模型,且鲜有考虑钻具屈曲的影响,预测结果与实测值存在较大误差。文章针对钻具的不同受力特点,分别采用软杆模型、刚杆模型和连续梁模型,在综合考虑钻具屈曲影响下,建立了考虑钻具屈曲的摩阻扭矩分段计算模型,通过模型计算值与现场钻井过程中实测值对比,模型扭矩和轴向载荷预测值与实测吻合好,平均相对误差分别为6%和7%。模型分析发现钻柱正弦屈曲与螺旋屈曲随轴向压力的增大交替出现;管柱的屈曲会随井斜的变化出现跳跃性变化;在滑动钻进过程中,如果忽略钻柱屈曲的影响,井口轴向载荷明显增大,实际传递到钻头的钻压将比预计的要小。在现场试验中,通过该模型计算的摩阻扭矩值及时调整了井口钻压及措施,有效降低了钻柱发生屈曲的程度,提高了钻井机械速度,对于指导现场钻井参数实时调整,提高钻井效率具有重要意义。

The existing friction torque analysis model often adopts a single rigid rod or soft rod model,and rarely considers the influence of drilling tool buckling,so there is a large error between the prediction and the measured results.In this paper,according to the stress characteristics of different drilling tools,the soft rod model,the rigid rod model and the continuous beam model are used respectively.Under the comprehensive consideration of the influence of drilling tool buckling,a piecewise calculation model of friction torque considering drilling tool buckling is established,and the model is verified by the measured data in the process of sliding drilling.The main conclusions are as follows:the predicted values of model torque and axial load are in good agreement with the measured values,and the average relative errors are 6%and 7%respectively.The sinusoidal buckling and helical buckling of drill string alternate with the increase of axial pressure.The buckling of the string will change with the change of well deviation.In the process of sliding drilling,if the influence of drill string buckling is ignored,the axial load of the wellhead increases significantly,and the actual weight on bit will be smaller than expected.In the field experiment,the friction torque value calculated by the model adjusts the drilling pressure and measures at the wellhead in time,which effectively reduces the degree of buckling of the drilling string and improves the ROP,which is of great significance to guide the real-time adjustment of drilling parameters and improve drilling efficiency.