Mechanical Analysis of Drill String Drag and Torque With the Condition of Irregular Borehole

Meng CAI, Lu WANG, Peng WANG, Meng LI


With the rapid development of drilling technology, air drilling technology and large displacement well, and horizontal well drilling technology are also known as the main directions of the future drilling development. Compared with conventional drilling mode, air drilling is particular, such as drilling fluid with low density, poor lubrication, large friction coefficient between the drill string and borehole, irregular borehole, well trajectory control difficulty, and so on. Along with the change of drilling condition, the stress of drill string is also changed. However, irregular borehole has a direct impact on the fatigue failure and the stress of drill string. Therefore, it is necessary to analyze drill string stress and influence factors in irregular hole. Based on the previous studies, application of drill string mechanics and statistical regression methods is used to study drill string drag and torque, and it can predict the drilling string stress state with the hole enlargement rate, meanwhile, it also provides a theoretical basis for gas drilling and complex drilling


Irregular borehole; Drill string; Drag; Torque; Mechanical analysis

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