Analysis of Drag/Torque Variation Law of Drill String in Second-Spud Horizontal Wells

Horizontal wells have become an important technical tool for oil and gas field development; however, the main technical difficulty in the drilling process is the prediction and control of the drag/torque of the drill string. To analyze and calculate the horizontal well drag/torque, this study establishes a mathematical model of the pipe string drag/torque based on the rigid rod model. Based on the pipe string force calculation, the sensitivity of drag/torque under different parameters in three types of well structure horizontal wells was analyzed, and it was found that under different parameter conditions, the drag/torque increased continuously with an increase in the horizontal section length, friction coefficient, and drilling fluid density of horizontal wells, and the carrying of stabilizers also increased the drag and torque of the drill string. Moreover, under different parameter conditions of the three well structure, the drag/torque of the second-spud horizontal well was the largest. The drag/torque of the second-spud horizontal well can be reduced by optimizing the wellbore trajectory design, drilling fluid system, and drill string combination. The field application achieved relatively good results.