I attended a presentation by DET CRC at the Australian Society of Exploration Geophysicists concerning the principles of the project and a current status.
The talk outlined the guiding principles of the program:
- The need to drill more boreholes in areas covered by near surface deposits which result in little or no evidence of mineralisation at depth.
- By drilling more boreholes, the likely “vectorisation” of mineralisation is more likely, leading to a greater chance of mineral discovery.
- Distribution of mines for South Australia showed a strong skew toward the giant Olympic Dam deposit. Studies of oilfields and other mineral deposits suggest a more even distribution of mine size, leaving the suggestion that the potential mines between an Olympic Dam and the much smaller copper mines of South Australia remain to be discovered.
- To remain competitive and to be able to drill more boreholes, the Australian exploration industry needs to significantly reduce costs. Total costs needs to be below $50 per drilled metre.
- A major plank of the project is the development of a drilling method that reduces drilling costs through a significant reduction in the drilling time – coiled tubing (less rods changes etc). Currently the focus is on no metallic coiled tubing.
Another focus of the project is to acquire more data during the drilling process:
- Assay samples at the surface through a mobile laboratory. (Downhole assay technology is not quite there yet).
- Logging whilst drilling technology. This has been used successfully in the oil industry for many years.
There seems to be two areas of focus for the logging whilst drilling:
- A probe which is sent to the core barrel at the end of drilling and whose sensors “poke” out the end of the barrel into openhole conditions. Data is recorded whilst the drill rods are being removed from the borehole. Only deviation and gamma data has been successfully collected to date and accurate depth of the data is still a challenge.
- Instruments stored on top of the core barrel and retrieved every time the core inner tube is retrieved. This is truly logging whilst drilling. From memory only deviation data has been collected using this method.
Some comments:
- The objectives of the logging whilst removing the drill rods will still require a certain degree of rig standing in preparing the instruments at the surface, delivery of the instrument to the core barrel, then pulling out the drill rods. To ensure data quality, the speed of drill rod retrieval will have to be monitored/slowed. There is very little time saved (if any) compared to a conventional inrod geophysical logging program.
- Much was said on the costs savings associated with less mobilisation of contractors to the drill site. With the mobile assay lab and logging whilst drilling equipment on site, it is likely the type of contractors mobilising to site may change but not the amount.
- This is nothing new. Gamma loggers have been put on drill and blast rigs before, commonly costing hundreds of thousands of dollars only to break and not be repaired because stopping the drill rig costs too much money.