When a new drill pipe is put into the well for use, it is recommended to loosen the joint twice at the wellhead, and the torque is slightly lower than the specified value. After confirming that the joint thread and sealing surface are in good condition, apply enough uniform thread oil, tighten the joint thread according to the specified torque, and then use it in the well. This running-in button operation is beneficial to strengthening threads. The surface hardness of petroleum drill pipe can improve the anti-jamming performance of thread and prolong the service life of drill pipe.
When butting drill pipe at wellhead, manual centering and tapping must be carried out to prevent the male connector from touching the end face or thread of the female connector and causing damage. Then, manually identify buckles with chain tongs, and introduce no less than two buckles before using hydraulic power tongs. Tighten the thread of drill pipe joint according to the specified torque (water holes of different steel grades, specifications and sizes need different tightening torques, which must be carefully treated differently).
Before each trip, the drill string should be unscrewed upside down, so that each pair of joints can be unscrewed once during three trips, so as to check the threads of each joint in time and reduce the problems such as sticking, tripping and drilling leakage. At the same time, the drilling tools should be moved in regularly. Change the stress state of drilling tools to make the stress of all parts of the whole set of drilling tools tend to be consistent, thus prolonging the service life of drilling tools and reducing the occurrence of early failure accidents of drilling tools. When drilling, reasonable rotating speed and bit weight should be selected according to formation, hole diameter and BHA structure. So as to ensure that the drilling tools are in ideal working condition and obtain satisfactory drilling efficiency. When the rotation speed of drill pipe reaches the critical rotation speed, the vibration frequencies generated by the rotation of drill pipe are longitudinal vibration, transverse vibration and torsional vibration.
When it coincides with the natural frequency of the drill pipe itself, it will cause resonance, which will make the whole drill string in the hole in a serious unstable state and make it bear extra fatigue stress, thus accelerating the fatigue failure of drilling tools. The greater WOB, the greater the resistance of the bottom hole bit. When WOB exceeds the critical permeability, it is easy to get stuck. When squeezed, the drilling tool will bend, leading to thread deflection and fatigue fracture. When drill pipe works in corrosive environment, deoxidizer and corrosion inhibitor can be added into drilling fluid.
Increase the pH value of drilling fluid to above 10; Select sulfur-resistant drill pipe; Use drill pipe with inner coating; On the premise of meeting the strength requirements, low-grade drill pipes and other corresponding measures should be selected as far as possible to reduce the influence of corrosion factors on drilling tools. When disassembling the drill pipe thread at the wellhead, the low-speed gear should be used first, and the hook spring should maintain a certain tension to ensure that there is no pressure between the thread surfaces of the two joints. After the joint is completely disengaged, lift the hook again to prevent the thread from being stressed and the upper drill pipe from colliding with the wellhead female joint under the action of spring force.
Post time: Nov-15-2021