Advanced logging tool

While advances in technology have enabled the Surface to In-Seam (SIS) drilling industry to improve the quality and quantity of the meters drilled while simultaneously providing geological surveying data for mine planning, the Underground In-Seam (UIS) drilling industry had, until recently, lagged behind.

One inherent weakness in current UIS drilling practices is the inability to maintain the bit within the confines of the coal seam. As a result, coal seam boreholes tend to undulate, frequently drilling out of the seam. This requires pullbacks and branching, which duplicates drilling meters and increases the risk of borehole collapse.

Although geo-steering can be achieved in horizontal boreholes using directional resistivity tools with shallow and deep depths of investigation, existing resistivity technologies did not meet the requirements for UIS drilling until now.

In collaboration with other research partners and support from Australian Coal Association Research Program (ACARP), Mining3 has been working on an Advanced Logging Tool project to develop Accurate Coal Interface Detection (CID) for geo-steering thus far lacking in the Underground In-Seam drilling industry.

Started in 2010, the aim of the Advanced Logging Tool project was to develop a suite of Measurement Whilst Drilling (MWD) tools for the Underground In-Seam (UIS) drilling industry that could facilitate the faster and more reliable drilling of holes.

After almost seven years and three phases of research and development, Mining3 has developed a resistivity measurement tool, which is believed to be the best solution available for geo-steering, not only for UIS drilling but also for SIS drilling. The operable wireless survey tool is the first measure-while-drilling product of its kind for the UIS industry.

Phase 1 of the Advanced Logging Tool project saw the development of the Superlogger tool, a pump down shuttle tool that provides high-resolution gamma density and directional passive gamma measurements. This tool has been deployed commercially in Queensland, and the phase was completed in 2012. The subsequent Phase 2 commenced in 2013 and involved the development of an intrinsically safe LWD platform and a prototype directional resistivity tool.

The directional resistivity tool, optimised for lateral in-seam drilling, was combined with a slimline logging-whilst-drilling (LWD) tool and has two capabilities:

• High-resolution directional imaging of the borehole surrounds with two depths of investigation, 0.4m and 1.2m
• At-bit directional coal interface detection

For applications where long drill rods can be used, a longer electrode sub can be utilised, increasing the depth of investigation.

Experiments were conducted in simulated conditions with lab prototypes of the imaging sub. 3D modelling of a full-size imaging sub was also conducted. The results of the physical experiments and 3D modelling demonstrated that the sensitivity at low contrasting roof and floor conditions were similar to published data from existing geo-steering tools. The tool also utilises the down hole motor and bit as a directional measurement electrode that increases the measurement distance and adds at-bit sensitivity to the roof and floor, dykes, and sills ahead of the bit.

The Advanced Logging Tool is a feat of engineering excellence and has the capacity to vastly improve productivity in underground in-seam mining operations. It will help change drilling practices by continuously identifying structures such as the roof and floor of the coal seam, as well as faults, dykes and sills. This will minimise delays during drilling, and achieve more reliable pre-mining drainage by drilling straighter holes. The reduction of unplanned longwall delays will result in significant cost savings for mining operations.

The final stages of the project, involving completing the design and manufacturing review, calibration tests, tool compliance with coal mines standards, lab and field experiments and finalising the user interface for UIS drilling have recently concluded. The tool will be undergoing site trials in a mine in NSW, Australia.