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Forced Vibration of Drill String and its Control in Directional Drilling

Salehi, Mohammad Mahdi | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48468 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Moradi, Hamed
  7. Abstract:
  8. Nowadays, economical extraction of oil and gas, and their products is an important issue for many countries. Up to now, vertical wells have been used for oil extraction but some wells exist that they cannot be reached by using vertical drilling; for example the wells under a sea. Therefore, this makes the governments and scientists determined to find a new way to reach them. Horizontal drilling is one of the new ways to reach such worthy wells. In this project, dynamics of the horizontal drill string is studied. Then, according to the forces that affect the dynamics of drilling, its vibration is analyzed. After finding the boundary conditions and normal modes of the system with using mode summation method, displacement of the bit is obtained. Then, dynamics of the horizontal drill string is simulated and the effect of increasing the number of modes and the mode convergence phenomenon is discussed. Then, due to instability of the system under special conditions, it is important to use a controller to stabilize the horizontal drill string. First, four inputs are employed to control and then four-mode-control system is applied to five modes. The result is acceptable. Finally, dynamic system response with implementation of two control inputs is studied and its performance is compared with the case of four control inputs. In both cases, it is observed that the controller acts efficiently in vibration suppression of the drill string and consequently achievement of stable conditions
  9. Keywords:
  10. Dynamics Models ; Vibration ; Control ; Forced Vibration ; Horizontal Drilling

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