长宁超长水平井钻井摩阻数值模拟分析

CN-H21-5井是四川长宁页岩气区块一口超长水平段水平井，存在高摩阻、高扭矩和钻柱屈曲变形等一系列页岩气水平井典型技术难题急需解决。为了控制钻柱屈曲变形和接触摩阻扭矩，基于Hamilton原理建立全井钻柱动力学模型并采用 ＨＨＴ-α法对模型求解，分析了造斜段造斜率和水平段钻具组合对摩阻扭矩的影响规律。通过数值模拟表明：增加造斜段的造斜率能够降低造斜段的接触摩阻总值，同时也能降低全井段的接触摩阻；小尺寸钻杆传递较大轴向力时会发生严重屈曲变形，导致接触摩阻不降反增；在水平段采用“大 ＋小”的钻具组合，既能减小钻柱发生严重屈曲变形的概率，也能降低水平段接触摩阻。结论认为，减少造斜段长度并提高水平段前半段钻柱尺寸能够有效降低全井的接触摩阻，该结论能为长宁页岩气超长水平井的降摩减阻提供理论支撑。

Numerical Simulation Analysis of Drilling Friction in Changning Ultra-long Horizontal Well

CN-H21-5 is an ultra-long horizontal well, which faces a series of typical technical problems of shale gas horizontal wells, such as high friction resistance, high friction torque and drill string buckling deformation in the ultra-long horizontal section. In order to control the buckling deformation and contact friction torque of the drill string, a full-well drill string dynamic model was established based on the Hamilton principle and the model was solved by the HHT-αmethod. The effect law of buildup rate and the BHA in horizontal section on the friction torque were analyzed. The research results show that: Increase the buildup rate of the build section can reduce the total value of the contact friction resistance of the build section, and at the same time can reduce the contact friction resistance of the entire well section; Serious buckling deformation will occur when a small-sized drill pipe transmits a large axial force, leading to the increase of contact friction resistance instead of decreasing; The use of a " big + small" drill tool assembly in the horizontal section can not only reduce the probability of serious buckling deformation of the drill string, but also reduce the contact friction of the horizontal section. It is concluded that reducing the length of deflecting section and increasing the size of drill string in the first half ofhorizontal section can effectively reduce the contact friction of the entire well, which can provide theoretical support for the friction and drag reduction of Changning shale gas ultra-long horizontal well.