Vibrations increase available power at the bit
Drill string vibrations generally are considered to be detrimental to downhole drilling equipment because they produce cyclic or fatigue loading. Tool joint failures, tubular washouts, and bit breakage are often fatigue related. On the positive side, dynamic forces applied to roller cone rock bits have the potential to increase penetration. This article quantifies the available vibration energy at the bit and shows how to control the level of energy through bottom hole assembly design and rotary speed. This work identifies the level of energy transmitted into the bottom of drill strings to maintain vibrations. This energy, which is available for making hole, is taken from rotary speed and torque supplied by the rotary table. Energy consumed by axial and torsional modes is approximately equal to steady drilling at the bit. Force level and location of impact point affects whether vibration energy is reflected back to the drill string or transmitted into the formation to make hole. MWD sensors can key force, displacement, and phase angle at the bit to establish vibration losses in the drill string. Vibration energy levels at the bit and direction of energy flow (into collars or into formation) can be controlled by bottom hole assembly design and rotary speed.
- Research Organization:
- Norton Drilling Systems, Norton Christensen Inc., Houston, TX
- OSTI ID:
- 6318029
- Journal Information:
- Oil Gas J.; (United States), Journal Name: Oil Gas J.; (United States) Vol. 82:10; ISSN OIGJA
- Country of Publication:
- United States
- Language:
- English
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