Abstract
Motion states of bottom hole assembly (BHA) have a great effect on the trajectory control and drilling efficiency while rotary drilling. In order to study the motion states of BHA in horizontal wells, a BHA dynamic model with the finite element method was established. Meanwhile, an indoor experimental setup based on similarity criterion was designed and built to verify the numerical simulation results. Finally, the effects of measuring positions, rotate speeds, weight on bit (WOB), and friction coefficients on the motion states were analyzed in numerical simulation and experiment. The results show that the experimental results can match well with the numerical simulation results. The motion states of BHA in horizontal wells can be divided into three kinds, including circular arc swing, "8" shape swing, and dot-like circular motion. The circular arc swing mainly appears at middle section of BHA and occurs through the collective result of gravity and tangential friction. The dot-like circular motion mainly appears at near-bit or near-stabilizer area because drill bit and stabilizer can steady the BHA at the center part of the wellbore. The "8" shape swing mainly appears at the crossed area and occurs through collective disturbance of the other two motions. Moreover, rotate speed and friction coefficient have promotions on the lateral vibration while WOB have a much smaller effect. Through analyses, related suggestions are given for the drilling engineering. The related conclusions and suggestions in this paper can help to further understand the lateral dynamic characteristics of BHA in horizontal wells and select suitable parameters for drilling engineering.
Highlights
With the development of drilling technology, horizontal wells have been widely used in the development of oil and gas fields [1]
The circular arc swing mainly appears at the middle section of bottom hole assembly (BHA) and it occurs through the collective result of gravity and tangential friction
The “8” shape swing mainly appears at the crossed area of the other two motion states, which occurs through the collective disturbance of circular arc swing and dot-like circular motion
Summary
With the development of drilling technology, horizontal wells have been widely used in the development of oil and gas fields [1]. As a widely applied technique, the horizontal well technique can effectively increase reservoir discovery, enlarge drainage area, and improve production, especially in shale gas wells [2]. It is usually subjected to a coupled vibrations including axial, lateral, torsional vibration [6]. These problems seriously restrict the effect of trajectory control and rate of penetration (ROP), and even lead to drill string damage and downhole accidents. Lateral vibration is considered the main reason for the BHA fatigue failure, damage, and borehole
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