Spectral mean normalization method for minimizing rotation effect from drill bit sounds

A data gathering and analysis system for facilitating a drilling operation of a subterranean formation, comprising:

• a computer processor;
• and
• memory coupled to the computer processor and comprising instructions, when executed causing the computer processor to
• generate a digitized data log of drilling sound waves from a drill bit while the drill bit advances through a depth range in the subterranean formation by cutting formation rocks to form a borehole, wherein the digitized data log comprises a plurality of drill bit sounds samples corresponding to a plurality of drilling depths throughout the depth range;
• convert the digitized data log into frequency domain data (FFT data);
• generating a first rotation rate cluster and a second rotation rate cluster from a rotation rate log of the drill bit advancing through the depth range;
• generate a first spectral mean curve (SMC) from a first portion of the FFT data corresponding to a first portion of the depth range where the rotation rate is within the first rotation rate cluster, wherein the first SMC represents effect of the rotation rate on the drilling sound waves for the first rotation rate cluster;
• generate a second SMC from a second portion of the FFT data corresponding to a second portion of the depth range where the rotation rate is within the second rotation rate cluster, wherein the second SMC represents the effect of the rotation rate on the drilling sound waves for the second rotation rate cluster;
• generate a scaled SMC from the first SMC and the second SMC, wherein the scaled SMC represents the effect of the rotation rate on the drilling sound waves as a function of the rotation rate;
• generate, based on the scaled SMC and the rotation rate log, a normalized FFT data from the FFT data, wherein the effect of the rotation rate on the drilling sound waves is reduced in the normalized FFT data;
• and
• facilitate the drilling operation based on the normalized FFT data.

A well system for performing a drilling operation of a subterranean formation, comprising:

• a drill bit coupled to a drill string that is suspended in a borehole penetrating the subterranean formation;
• and
• a data gathering and analysis system configured to
• generate a digitized data log of drilling sound waves from the drill bit while the drill bit advances through a depth range in the subterranean formation by cutting formation rocks to form the borehole, wherein the digitized data log comprises a plurality of drill bit sounds samples corresponding to a plurality of drilling depths throughout the depth range;
• convert the digitized data log into frequency domain data (FFT data);
• generating a first rotation rate cluster and a second rotation rate cluster from a rotation rate log of the drill bit advancing through the depth range;
• generate a first spectral mean curve (SMC) from a first portion of the FFT data corresponding to a first portion of the depth range where the rotation rate is within the first rotation rate cluster, wherein the first SMC represents effect of the rotation rate on the drilling sound waves for the first rotation rate cluster;
• generate a second SMC from a second portion of the FFT data corresponding to a second portion of the depth range where the rotation rate is within the second rotation rate cluster, wherein the second SMC represents the effect of the rotation rate on the drilling sound waves for the second rotation rate cluster;
• generate a scaled SMC from the first SMC and the second SMC, wherein the scaled SMC represents the effect of the rotation rate on the drilling sound waves as a function of the rotation rate;
• generate, based on the scaled SMC and the rotation rate log, a normalized FFT data from the FFT data, wherein the effect of the rotation rate on the drilling sound waves is reduced in the normalized FFT data;
• and
• facilitate the drilling operation based on the normalized FFT data.