Detecting and reducing bit whirl

Claim 1

A method of detecting the destructive vibration of a drilling component in a borehole, comprising: monitoring the acceleration magnitude and the frequency of the lateral vibration of said drilling component using MWD techniques with vibration transducers located in or near said drilling component wherein said lateral vibration is measured in X and/or Y coordinates acording to the relationship: X=RΩ.sup.2 cos (ω-Ω)t-RΩ' sin (ω-Ω)t-rω.sup.2 Y=RΩ.sup.2 sin (ω-Ω)t+RΩ' cos (ω-Ω)t+rω which R is the whirling radius, Ω is the whiring frequency, Ω' is the time derivative of Ω, r is the distance between the center of the drilling component and the accelerometers, ω is the angular velocity or the RPM, and ω is the the derivative of ω; determining the acceleration magnitude of the lateral vibration of said drilling component; determining the peak of the power spectrum of the acceleration magnitude occurring in the frequency domain in said lateral vibration; comparing said peak magnitude with a threshold magnitude in said frequency domain indicative of the possible onset of destructive vibration of said drilling component; and signalling onset or the occurrence of destructive vibration of said drilling component when said peak magnitude in said frequency domain reaches or exceeds said threshold magnitude.

Claim 2

A method of detecting the destructive vibration of a drilling component in a borehole, comprising: monitoring the acceleration magnitude and the frequency of the lateral vibration of said drilling component using MWD techniques with vibration transducers located in or near said drilling component wherein said lateral vibration is measured in X and/or Y coordinates acording to the relationship: X=RΩ.sup.2 cos (ω-Ω)t-RΩ' sin (ω-Ω)t-rω.sup.2 Y=RΩ.sup.2 sin (ω-Ω)t+RΩ' cos (ω-Ω)t+rω which R is the whirling radius, Ω is the whiring frequency, Ω' is the time derivative of Ω, r is the distance between the center of the drilling component and the accelerometers, ω is the angular velocity or the RPM, and ω is the the derivative of ω; determining the acceleration magnitude of the lateral vibration of said drilling component; determining the peak of the power spectrum of the acceleration magnitude occurring in the frequency domain in said lateral vibration; comparing said peak magnitude with a threshold magnitude in said frequency domain indicative of the possible onset of destructive vibration of said drilling component; and signalling onset or the occurrence of destructive vibration of said drilling component when said peak magnitude in said frequency domain reaches or exceeds said threshold magnitude.