Experimental evaluation of rock disintegration detection in drilling by a new acoustic sensor method

Abstract

A simple and reliable method for monitoring the rock properties in drilling is recognized as a global challenge, especially for cluster and infill development well drilling in oil and gas production. To improve the existing limitations in the detection of formation lithology in drilling systems, an acoustic sensor approach for rock disintegration in the drilling using a polycrystalline diamond compact (PDC) drill bit is developed and evaluated. In this paper, we report the application of a special acoustic sensor device to qualitatively survey rock disintegration by rotary drilling. In this work, an acoustic focusing component is designed to assist a condenser microphone in detecting signals emerging in the process of drilling as an integrating information resource. A time-frequency with zoom fast-Fourier-transform analysis method is presented to recognize the acoustic signal features in breaking different rocks. Additionally, principal component analysis and Support Vector Machine method are used to check the qualitative analysis results for the monitored rock information. An experimental investigation considered four types of rock broken by a PDC drill bit with drilling weights ranging from 5 to 12.5 kN and drilling rates ranging from 64 to 128 r/min. To verify the reliability and accuracy of our acoustic rock detection method, two sensors installed in the orthogonal direction are examined. Furthermore, the coherent analysis was used to reveal the correlation of the output auto-correlation spectrum for each measurement. The results show that there is a good average percentage of lithology calculated by the time-frequency analysis results between the acoustic signal features and different types of rock. Accordingly, the acoustic sensor approach can help enhance the detection of rock properties in drilling systems, laying the foundation for quantitative lithology identification in more complex drilling.