关键词: 页岩气, 超长水平井, 钻柱动力学, 摩阻

Abstract: 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 of horizontal 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.

Key words: shale gas, ultra-long horizontal well, drill string dynamics, friction