Field trails of DET CRC's RoXplorer CT rig (above) demonstrated proof of concept for a drill that costs around $50/metre down to a depth of 500 metres and weighs less than 10 tonnes. Courtesy of the DET CRC

An Australian research consortium believes it has made a technological breakthrough that will relieve some of the problems that have plagued the exploration sector in recent years by adapting drilling technology from the oil and gas industry to create a safer, more economic and flexible drill for mineral exploration.

In June, the Deep Exploration Technologies Cooperative Research Centre (DET CRC) finished the third and final field trial for its coiled-tubing (CT) drill rig for greenfield exploration, dubbed the RoXplorer. The field trials for the project proved the team at DET CRC had achieved their original goal of developing a drill that would cost $50/metre down to a depth of 500 metres and weighs less than 10 tonnes with ancillary safety and environmental benefits. According to DET CRC drilling program leader Soren Soe, that is compared to around $500/metre for diamond drilling in the peak drilling years and $300/metre for reverse circulation drilling.

All three field trials took place in Australia over the course of about seven months, the first two in the state of South Australia in harder consolidated rock settings and the third in Horsham, Victoria, in an unconsolidated environment with an underlying basement. “We were basically trying to increase the readiness level of the technology around the RoXplorer system,” said Soe. “We had very successful trials in both states.”

The genesis for the project was AMIRA International’s Drilling Technology Roadmap, which was developed in the mid-2000s to explore new drilling practices. The DET CRC, created in 2010, grew out of AMIRA’s initial effort as an R&D venture to determine a cheaper and safer method for exploration.

According to Soe, major miners, including BHP, Barrick, Vale, Newcrest Mining, Gold Fields and Anglo American, wanted to “make a fundamental change in the exploration drilling industry and they realized that it would not be a change that could be driven from the service providers in the industry alone.” It would simply be too expensive and distracting for them to develop on their own.

So with AU$155 million in funding from the government of Australia and its major industry sponsors, the DET CRC allocated some of that funding to develop a mobile, light-weight drill rig that would be a cheaper alternative to diamond drilling and produce more accurate samples than reverse circulation, and could drill in both hard rock and unconsolidated formations.

Rig ready

After researching several different options, the DET CRC decided in 2015 to move forward with CT technology, a practice inspired by similar drill rigs used in the oil and gas industry. Unlike most drills, where an operator must stop drilling every three, six or nine metres to add a drill rod, the CT drill consists of a single continuous drill pipe made of malleable steel on a reel.

One of the advantages is the elimination of rod handling, which has long been a safety hazard for drillers and offsiders. According to Soe, about half of the injuries in mineral exploration are from rod handling or rod transportation. “You have a lot of finger injuries when you are connecting or disconnecting, and handling rods,” said Soe. “And by having a CT drill rig, you would have almost zero rod handling involved.”

The RoXplorer also applies constant in-hole pressure as the operator never has to stop drill fluid circulation, which increases borehole stability when drilling unconsolidated formations in particular. Constant fluid pressure on the borehole walls means operators are less prone to get stuck pipe or hole collapse.

The fact that the CT drill rig has performed so well with unconsolidated formations is particularly encouraging to Soe. “It opens up a lot of formations for this type of drilling, that we are able to drill these unconsolidated formations, and continue to drill through the basement where you typically find the mineralization,” he said.

The CT rig drills micro-boreholes at a diameter of 60 millimetres, compared to a typical borehole with a diameter of around 75-100 millimetres or even larger for reverse circulation. “That’s the smallest size you would normally drill anything with, but we drill that pretty much all the way down, which is definitely not common,” said Soe. In line with the DET CRC’s objective of reducing environmental impacts of a drill rig, micro-boreholes use less energy to drill and create less waste as they remove less material. This is significant as miners drill deeper to reach potential mineral deposits.

The DET CRC has also figured out a way to drill in a closed loop, meaning there are no mud pits or mud sumps. “We are using mechanical processing of the drilling fluid in a closed loop system,” said Soe. “We don’t have any fluid on the ground. It’s all contained in solids removal units.”

Robbie Rowe, manager of research integration for drilling trials and products at the DET CRC, said the technology can be used “in almost all exploration that involves looking for mineral deposits and is most suited for exploration below post-mineral cover.” That means it could be used to explore anywhere – not just in Australia where it is being developed – for example, under the gravels of Chile, for Carlin deposits in Nevada, and under the glacial till cover in Canada.

According to Soe, the CT drill rig would be a game changer. “If you can drill a lot of cheap, fast holes, you open up another way of doing exploration or another way of doing prospecting,” he said. “In the old school, you follow the trace on the ground or the outcrop to find the source and the mineral deposits. If you drill enough holes and understand deposit footprints, this will allow you to vector to the source of the mineralization. If we manage to deploy all our technologies efficiently, it will lead to a new type of prospecting.” That could mean drilling wider-spaced drilling patterns. Coupled with another technology the DET CRC is developing – its Lab-at-Rig system, which would analyze assays in a matter of hours rather than weeks – companies could quickly and efficiently explore and target prospective properties.

Ironing out the kinks

One of the main challenges for the team at the DET CRC was how to improve the fatigue life of the coil. “It’s a little bit like a paper clip, when you bend it and stretch it many times, it fatigues and fails between your fingers,” said Soren. The DET CRC was able to bring the fatigue life to 1,000 trips into the ground up from 35 for the initial drill rig it tested. Soe declined to give specifics, but he said the achievement was the result of tweaking elements of the coil material, design of the machine, and optimizing the overall system with techniques like micro-tripping.

Another was how to cut hard rock efficiently using a CT drill rig. When the DET CRC started researching the technology five years ago, “you couldn’t cut rock at any cost-economical rate at all,” said Soe. With the technologies available at the time, they were only able to cut hard rock about 25 millimetres per minute in a hard-rock environment. By optimizing the pressure, the drilling technology, the systems, and improving their sensors, the DET CRC was able to improve the drilling rate to 500 millimetres per minute.

Coming commercialization

With the successful proof of concept, the RoXplorer is set to be offered to industry sponsors Boart Longyear and Imdex for possible commercialization in November, allowing the companies first right of refusal to the technology. Once commercialized, the technology will be made available first to the mining companies involved in the DET CRC and then to the industry as a whole, although Rowe said it is difficult to put a date on when that will be.

“It’s years away realistically,” he said. “Whether that’s two years away or five years away, we don’t know. And I think that really is up to a company to try and take this on and develop it and make it into a commercial product.”

Nevertheless, Rowe is adamant that the RoXplorer is potentially a transformational technology that will impact mineral exploration along with the rest of the work being done at the DET CRC. “The key thing is that the DET CRC is working on technologies for the short to medium term; the incremental technology that people can use on current drill rigs and current technology,” said Rowe. “They’re working on things that can make the difference tomorrow or within a few years, but at the same time, they’re working on truly disruptive technologies that will change the way we drill holes in the ground and therefore how we explore.”