Drill string axial vibration attenuator

Abstract

The drill string axial vibration attenuator (10) is installed in the bottom hole assembly (BHA) of a drill string to attenuate axial and torsional vibrations of the drill string. The vibration attenuator (10) includes a massive elongate stabilizer (14) installed in a sealed chamber (12) that is, in turn, rigidly installed within the BHA of the drill string. Clearance between the inner wall of the chamber (12) and the stabilizer (14) is provided to preclude frictional interference therebetween. The stabilizer mass (14) is supported from below by a compression spring (18) and a shock absorber or damper (24) at the top to allow movement of the mass (14). The stabilizer (14) substantially reduces or eliminates axial and coupled torsional vibration of the drill string when the mass of the stabilizer (14), the rate of the spring, and the damper stiffness are properly configured.

Description

TECHNICAL FIELD[0001]The present invention relates generally to earth boring and drilling equipment, and particularly to a drill string axial vibration attenuator for damping or attenuating undesired axial motion in a drill string during drilling operations.BACKGROUND ART[0002]The problem of drill string vibration has been recognized as one of the prime causes of deterioration in drilling performance. These vibrations may be lateral, torsional, or axial. Field observations have indicated that drill strings can exhibit severe vibrations that may become even more severe at the bottom-hole assembly (BHA), which comprises the drill collars, stabilizers, and the drill bit, and may also include other logging tools and instruments.[0003]This application is directed to axial and torsional drill stem vibrations, and means for reducing or eliminating such axial and torsional vibrations. As the drill bit is penetrating the underlying formation during the drilling operation, the normal reaction...

AI Technical Summary

Benefits of technology

The patent describes a way to adjust the suspension system of a drill bit to reduce vibrations during drilling. This is done by adjusting the mass, spring rate, or stiffness of the suspension components, which help to dissipate the vibrations and reduce them. The process takes into account factors like the type of drill bit, formation type, and the weight of the drill string. The suspension system helps to improve the stability and efficiency of drilling operations, making them more reliable and effective.

Problems solved by technology

The problem of drill string vibration has been recognized as one of the prime causes of deterioration in drilling performance.

Field observations have indicated that drill strings can exhibit severe vibrations that may become even more severe at the bottom-hole assembly (BHA), which comprises the drill collars, stabilizers, and the drill bit, and may also include other logging tools and instruments.

As the drill bit is penetrating the underlying formation during the drilling operation, the normal reaction force or weight-on-bit (WOB) may become excessive and fluctuate, resulting in axial vibration in the drill string.

This is known as “bit-bounce.” Excessive axial vibration or bit-bounce may result in reduction of the rate of penetration (ROP) of the drill bit and / or damage to the drill bit, adverse effects upon telemetry tools and data conveyed to the surface, and fatigue of the drill pipes that form the drill stem.

All of these factors result in decreased efficiency in the drilling process and increased costs of operation due to the need to replace various components more frequently than would be the case without such axial drill string vibrations.

Excessive torsional vibrations may eventually result in limit cycles where the BHA rotary speeds are bounded between zero and two or possibly even three times the designated rotary table (rotary drive for the drill stem) speed.

This “stick-slip” phenomenon is also detrimental to the drill pipes and string, the drill bit, logging tools, and to the entire drilling operation.

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