Drill string vibrations can significantly impact the performance of oil and gas drilling operations. They can lead to premature wear and tear of drilling equipment, resulting in fatigue and induced string failures such as drill pipe washout. Additionally, they decrease the drilling energy delivered to the bit. Therefore, it will cause a drop in the directional control following drilling performance.

We must remember that low levels are usually harmless. However, severe ones are destructive. As improving drilling performance is crucial to the economic interests of the oil industry, minimizing drill string vibrations is of utmost importance. And Yes, you can control them, but to a degree.

There are many consequences of drilling with severe vibrations:

1- Vibrations will cause cyclic fatigue in drill pipe, drill collar, drill string, or bottom hole assemblies that may lead to twist-off problems and following fishing operations.
2- It may cause hole enlargement.
3- In addition, these phenomena may increase the drilling bit wear rate and cause the failure of one of its cones or parts, slowing down the drilling operation.
4- Damage to the directional deflection & surveying tools such as MWD tools, Rotary Steerable Systems & Mud Motor

Reduce drilling performance.

The Root Cause of the Drilling Vibrations:

Vibration, in simple terms, refers to the movement back and forth. To create this movement, a force of excitation is necessary. Various factors contribute to vibration during drilling operations, including the drilling parameters, mud pumps, Interaction between the rock lithology and drill bit, downhole motor, drill string rotation, and the well bore interaction. Generally, we can’t avoid these factors while drilling a hole. However, we can decrease their effect.

If the natural frequency of the drill string matches the frequency of vibration, it can cause resonance and severe vibrations. Ideally, there are three modes of vibrations: axial, torsional & lateral. They are often coupled, which means that they affect each other.

Axial Drill String Vibrations:
Have you ever wondered how a tricone bit drilling into a piece of chert creates a persistent three-lobe pattern on the hole bottom? It’s actually quite fascinating! As the cones roll over the chert, the bit experiences an upward force with a frequency three times that of the rotary speed. If this frequency happens to be close to a resonant axial frequency of the string, resonance occurs, and the three-lobe pattern is born.