Book Description

One of the main problems encountered in impregnated diamond core drilling operations for deep mineral explorations is to remotely infer bit wear state and to drill with optimal performance at great depth. Currently the optimal drilling performance relies heavily on operator experience. This paper aims to assess the feasibility of acoustic emission (AE) monitoring of the impregnated diamond drilling process and to establish relations between AE signals and diamond drill bit wear to improve overall drilling performance. AE relations with various drilling parameters have also been investigated to understand signal characteristics in relation to operational parameters. Echidna drill apparatus that simulates field exploration diamond drilling on a small scale is used to monitor AE during rock bit interaction. AE sensors were attached to both the drill and the rock in question to record acoustic signals being emitted whilst drilling. Two different tests viz. 'step tests' and 'wear tests' were carried out. Step tests on the Echidna drill include stepping down the depth of cut from 130μm to 0μm, while cutting speed is constant. Secondly, wear tests performed on the Echidna drill, involves accelerating the wear rate of the drill bit via two different types of tests, both in highly abrasive rock. Based on the step test results, a series of linear relations were developed. These relations are capable of estimating the depth of cut, weight on the bit (WOB) and torque on the bit (TOB) by simply using time spectrum of the AE signals. Wear tests also showed that AE amplitudes start to trend down over the time of accelerated wear.