In-Seam Drill Monitoring and Bit Location System (Stage 2)

This report documents the work conducted during Stage 2 of an ACARP project entitled 'In-seam drill monitoring and bit location system'. The project is part of an integrated in-seam drilling research program which aims to increase the effectiveness of underground drilling operations. It is a joint collaboration between BHP Research, BHP Australia Coal Collieries and Kembla Coal and Coke Pty Limited. The project consists of three stages: Stage 1 of the project was completed in December 1994 and Stage 2 completed in May 1996.  The project is divided into three components:

• The construction of a drill monitoring system for recording parameters associated with drilling. Changes in drilling parameters are used to predict geological structures encountered while drilling.

• The construction of a drill bit location system that will be used to determine the position of structures located by the drill monitor and also aid in optimally positioning gas drainage holes.
• The development of intrinsically safe computing hardware and software to integrate drill monitor data with bit location data.

A drill monitoring system, namely the Underground Drill Monitoring System (UDM), has been developed and successfully tested at Cordeaux and Appin Collieries. Monitoring using this system has provided valuable information on structural anomalies and gas drainage processes in potentially outburst-prone areas. A total of 1935m of drilling was logged using the UDM system. Data were processed and compared with the available geological information. Very encouraging results have been obtained.

Intrinsically safe computing hardware for on-site data recording has been developed for use with several sensing systems. This hardware was recently approved by the Department of Mineral Resources NSW. The IS computer has processing power similar to a 486 based PC and includes 680Mb of disk storage. Two prototype units have been produced for underground applications.

Stage 3 of the project will involve the integration of the drill monitor and IS computer and the development of processing software for routine and efficient handling of monitored data.

Introduction

In most underground coal mining operations, in-seam drilling is an integral part of exploration, gas drainage, production and safety practices. Typically long holes, of lengths greater than 500m, are drilled to explore proposed mining areas, and to detect any potential geological hazards, such as outburst zones and unfavourable water conditions. Shorter holes, typically up to 250m in length, are drilled for cross-panel gas pre-drainage and probing ahead of development faces to detect geological structures.

An efficient and effective drilling program is extremely important to mining operations as it provides vital mine planning information, affects timing and duration of pre-drainage and, in some mines, is the principal tool for outburst control. According to the findings of an ACARP task force (Hanes 1993), in seam drilling technology is the top priority for underground coal mining exploration R&D. The report also highlights the need for an economical and reliable system for locating the drill bit in the X-Y plane, and a system of detecting structures in drill holes.

The task force has responded to these requirements by developing an integrated research initiative for in-seam drilling within ACARP. As part of this program, BHP and Kembla Coal and Coke have conducted an ACARP project to develop a drill monitoring and bit location system for in-seam rotary drilling of gas drainage and short exploration holes. These developments aim to improve safety and productivity by providing better knowledge of structures while drilling and the correct placement of holes to drain the areas.

The first stage of the project (ACARP project C3070), conducted in 1994 and reported earlier (Danell et al, 1995), has confirmed the effectiveness of a prototype intrinsically safe (IS) drill monitoring system and determined the feasibility of an acoustic bit location system. This report presents further results of the drill monitoring system, bit location efforts, and the development of an intrinsically safe (IS) data acquisition and processing system.

Conclusions

The Underground Drill Monitoring System has been developed and successfully tested at Cordeaux and Appin Collieries. Also, intrinsically safe computing hardware for on-site data recording has been developed for use with several sensing systems. This hardware was recently approved by the Department of Mineral Resources, NSW. The IS computer has processing power similar to a 486 based PC and includes 680Mb of disk storage. Two prototype units have been completed for underground work.

The UDM system has provided valuable information for Bulli seam workings, in particular on structural anomalies and gas drainage processes in potentially outburst-prone areas. As presented in the case studies the UDM system proved to be an effective tool not only for detection of outburst prone structures but also for mapping of other smaller structures.

A total of 1935m of drilling was logged using the UDM system. Data was processed and compared with the available geological information. Very encouraging results have been obtained, indicating the high potential of the UDM system in obtaining quality information in comparison to other currently available systems, such as In-Seam Seismic and Radio Imaging Measurement System (RIM).

Work on a bit location system based on acoustic techniques has been suspended. This is due to developments in other technologies that are likely to lead to systems that are more cost-effective for use in underground production situations.

The Underground Drill Monitoring system (UDM) in its current form can be used to provide an indication not only about conditions related to outburst risk assessment but also about general geology of the area. A high number of the detected geological structures could have impact on the roof stability of a given area. By providing such information to colliery management a significant improvement to the safety of miners can be achieved. The UDM in this case would be used as an awareness tool. The information can be used not only to alert a mining crew, but also for better planning of the roof support system.

Recommendations

The Underground Drill Monitoring (UDM) system has been demonstrated to reliably generate coal strength information along in-seam holes in the Bulli seam. This data is generated at a high resolution with a sample every 15mm. It has been observed, however, that the number of stages of data processing of the UDM system is a barrier to full implementation of the system in the Australian underground coal mining industry.

The DSG Logger was developed in this project to enable immediate processing of drill monitoring data. Currently it is operating with the UDM software. The remaining major steps are the physical relocation and connection of the unit and the interpretation of the borehole logs. The borehole log interpretation will require input from a skilled person for the foreseeable future and this is the most valuable step in the operation.

It is recommended that the project progress to Stage 3, which will entail development and testing of software to implement the simplifications outlined (in Table 7.1) This development would take full advantage of the DSG Logger system and would result ultimately in the system automatically logging the data and preparing a borehole log immediately after completion of the hole, while the unit is still underground. It is expected that only minimal data interpretation will be done on site. The system would be designed to be used by a drill operator during relocation and connection. Stage 3 is regarded as essential to ensure full transfer of the technology to the industry.

It is also recommended that an assessment of incorporating the borehole log data into commercial mine planning and geological data presentation software be conducted. It is recommended that this step is only followed after final data verification conducted by the site geologist. This would enable the most efficient incorporation of the drill monitoring data into the normal mine planning process.