Co-Ordination of In-Seam Drilling Research

In-seam drilling technology and priorities for its application have changed considerably since 1993 when the scoping study into in-seam drilling was conducted. Technological advances have mainly been due to the changing attitude in the industry to in-seam drilling and its role in defining whether mining can be conducted.  The main technological developments in in-seam drilling since the commencement of ACARP have been made by mine operators and contractors, with assistance from suppliers, to solve their problems in the short term. ACARP funded research has resulted in prototypes which have either been completed or will be completed over the next two years and which will take in-seam drilling technology in to the next generation.  The continuing ACARP support of the project, "Co-ordination of In-seam Drilling Research" has facilitated the technological advances through promotion of communication amongst all players and through the monitoring of the research projects.

When this project commenced with a scoping study of in-seam drilling conducted in 1993, there were many problems listed by contract drilling companies and by mines who used in-seam drilling. Drilling techniques were improving, but there was much duplication of effort.

The research and developments initiated and/or encouraged by the Exploration Task Force will eventually help the goals of the industry to be achieved by advancing in-seam drilling technology into its next generation.

Improvements to In-seam Drilling

Within the next few years the major improvements to in-seam drilling as a result of the ACARP funded projects will include:

• The recognition and location of geological structures while drilling directionally controlled holes, using behind-the-bit monitoring of torque, thrust and RPM developed by the AGA consortium, combined with a radiometric tool developed by the CTME. This tool should enable long holes to be drilled within a defined section of the seam without the need for branching to intersect the roof for horizon control. The prototype tool should be available by end 1998. A capacitance tool and radar under development by CMTE have been shown to detect structures when run in the hole post drilling. Discussions with possible commercial interests are current. 
• The development of 'measure while drilling' geophysical tools. These tools together with the maintenance of borehole stability and testing of gas contents will be facilitated by the borehole pressurisation system of AGA. This tool has been developed and is ready for underground trials. 
• Recording of rotary drill rig data facilitated by the BHPR IS 486 PC monitored ProRam drill. This system is now complete and has been demonstrated as being capable of detecting outburst prone structures during drilling. The technology could be easily adapted to monitor most drill rigs. The recording system should be available to the industry soon. Although there has been repeated calls for drill rig monitoring, the industry has not been pressuring BHP to commercialise the unit. Industry appears to be waiting to be supplied with the final product rather than adapting the technology to the current rigs. 
• Survey while drilling rotary holes should soon be possible using a survey tool being designed by Sigra in combination with the AGA torque, thrust, RPM device, should enable recognition of structures during drilling. Trials of the torque, thrust and RPM tool have shown that the lithology being drilled can be readily recognised. 
• A simple borehole flow meter developed by Sigra should be available during 1997 to enable remote monitoring of flow. 
• A system for logging gas contained in the drill fluid designed by Lunagas is progressing with support from BHP Collieries. 
• The ACIRL calliper probe was field tested and redesigned to allow for shortcomings in the initial prototype and a second prototype is undergoing trials. 
• A research facility for testing, designing and analysing drill rod joints now exists at the University of Queensland in conjunction with Sigra. Drill rod joints have been tested and have been found inadequate for very long hole drilling. Owing to a lack of tensile strength which is exacerbated if joints are not properly made up. 
• The use of waterjet assisted drilling of in-seam across panel drainage holes to enable the drilling of straighter rotary holes. This project by CMTE has progressed well in trials. The indications to date are that WJA drilling produces straighter holes than rotary, the use of centralised jets should keep the bit in the seam and WJA drilling reduces bit wear substantially. Water jet assisted drilling might enable a return to less costly rotary drilling for across panel drainage holes.

Benefits to the Industry

It is difficult to determine a cost saving for the expected achievements, however, the savings have to be at least equivalent to the savings involved in adoption of a MWD survey system over a single shot survey system with increased productivity and safety. The application of the new technology to outburst mines might mean the difference between mining and not mining.

The NSW Chief Inspector of Mines insists that each outburst mine should only mine using outburst mining procedures if they cannot prove effective drainage and the presence of no structures. This would cripple those mines.

The trend towards replacing much of the rotary drilling with directional drilling to achieve better accuracy or at least the knowledge of where holes have gone, has cost industry an estimated extra $17 million per year over the last couple of years.

If a suitable MWD survey tool could be used during rotary drilling to provide accurate location of the holes without the current burden of post-drill survey, or if waterjet assisted rotary drilling can effectively produce straight holes, the high cost of guided drilling for drainage could be reduced.

The adoption of the tools being developed should also increase productivity of directional drilling by at least 20%.

Most of the major in-seam drilling problems identified by operators are being addressed and should be solved by developments which have occurred or commenced in the last two and a half years, some as ACARP funded research, some as mine site initiatives and some by suppliers in response to industry requirements.

Support by ACARP for a Co-ordinator of in-seam drilling research has facilitated these developments though improved communication between all players and minimisation of duplication. To continue these benefits, the project has been extended for another year from 1 April 1997.