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Coupled Vibration Analysis of Directional Drilling String Considering Effect of Drilling Mud

Taheran, Farshad | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44009 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Ahmadian, Mohammad Taghi; Farrahi, Gholamhossein
  7. Abstract:
  8. Vibration is one of the most important factors in design, operation and lifetime of drill strings. There for, investigation of vibrations in drill string, like every other rotary machine, is very important. The main goal of this research is developing a nonlinear model for a drill string system dynamics in an inclined well. Effects of drilling mud flow rate, weight on bit, angular velocity along with viscous damping, on the stability and vibration of a drill string are studied. Dynamic equation of the model is developed considering axial displacement and lateral bending geometric nonlinear coupling. The effect of drilling mud flow is modeled using Paidoussis formulations. Equation of motion for the rotating drill string is derived using Lagrangian technique and implementing finite element method to solve these equations. The stabilizers are modeled by dropping the coincided nodes. These results represent the significant effects of non-linear terms. Also, the effects of drilling mud flow rate and weight on bit on the natural frequencies and time responses are illustrated. Increasing drilling mud flow rate causes decreasing of natural frequencies and vibrational amplitude. Furthermore, increasing weight on bit leads to decreasing natural frequencies and increasing vibrational amplitude
  9. Keywords:
  10. Drill String ; Stability ; Nonlinear Vibration ; Angular Velocity ; Drilling Mud Flow Rate ; Weight on Bit

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