Method and equipment for the express-control of fracturing in adjacent rock mass by optical borehole logging

Abstract

Safety of mining should be based on reliable and timely information about the structure of the adjacent rock mass. Today, the main sources of such information are the acoustic and telemetering surveys in boreholes. At the same time, ultrasonic logging measurements are highly labor-intensive, and video imaging of borehole walls features complexity and subjectivity of image interpretation. In this paper, we propose a new method based on optical scanning of borehole walls using discrete photosensitive elements. The method allows identifying cracks intersecting the borehole, as well as determining their orientation angles α and β. To implement the method, an eight-channel optical logging probe and a dedicated software have been developed, which make it possible to determine the angles α and β in an automated mode immediately after scanning. Based on the representative sampling of rocks of various genotypes, it is experimentally proved that variations in the roughness and color of the scanned surface have no significant impact on the effectiveness of the proposed method. The laboratory studies show that thy use of the weighted least square method according to the Levenberg–Marquardt algorithm to approximate data from eight photosensitive elements of a logging probe can improve the determination accuracy of crack geometry and to detect fractures with an opening of 0.5 mm and wider at high reliability. Furthermore, the advantages of the method include acquisition of measurement information in the form of logging curves ready for joint processing with the results of the other logging methods, for example, ultrasonic logging.The study was supported by the Russian Science Foundation, Project No. 21-77-00046.