水平井钻柱摩阻扭矩分段计算模型

Segmental calculation model for torque and drag of drillstring in horizontal wells

根据水平井接触和受力特点,利用分段计算方法,建立水平井钻柱摩阻扭矩计算模型;采用三维纵横弯曲梁理论,计算钻柱BHA(底部钻具组合)段摩阻扭矩;采用软杆模型,求解BHA以上钻柱段的摩阻扭矩;对井眼曲率变化较大及刚度较大的加重钻杆井段软杆模型加以修正,考虑钻柱屈曲的影响,建立适合水平井的摩阻扭矩三维分段计算模型.应用结果表明,该模型计算精度较高,平均相对误差为10%,可为现场实践应用提供技术参考.

In horizontal well dragging,torque of drillstring is a key factor that affects the extension of the horizontal displacement and well track control.Based on force features of the horizontal well,the paper calculates torque and drag of drillstring separately and establishes the calculation model.The torque and drag in BHA section is calculated applying the beam-column theory,and soft string model is used in upper BHA section,the modified soft string model is used for sections with large well curvature or heavy weight drill pipe by taking into consideration the stiffness of drillstring.In the given mechanical model,considering buckling behavior of drillstring effects,the segmental calculation model for torque and drag of drillstring in horizontal well is established.Field example shows that the model is of high precision and average error of the results in theoretical forecasting is 10% in comparison with the field test values,the result is reliable and offers some references for field application.