Water-driven percussion drilling techniques, such as that used by the RoXplorer(R) coiled tubing drill rig, return a rock sample as cuttings that are carried to the surface by the circulating drilling fluid. This drilling technique does not deliver a core sample. In order for the RoXplorer(R) to be effective as a mineral-exploration drill rig, it is critical to develop robust, representative and repeatable sampling techniques for the rock cuttings and to establish with confidence the depth interval from which the sample was derived. The RoXplorer(R) produces more than 7 kg/m of cuttings every few minutes (rate of penetration dependent) that are carried to the surface by the drilling fluid with a fluid return rate of 80-150 L/min. The cuttings, which range in size from <10 mu m to 5 mm, require extraction from the drilling fluid and preparation prior to analysis. Subsampling of the fluid/cuttings stream can reduce the sample size to allow easier processing. A modified static cone splitter and ancillary flow-control system were designed and tested during field deployment of the RoXplorer(R) drill rig in South Australia in February 2017. We drilled a vertical hole with RoXplorer(R) starting 10 m to the northeast of an existing vertical diamond drill hole with well-characterised, shallow-dipping sedimentary and volcanic units. This allows comparison of drilling performance and sample quality against industry-standard drilling and sampling techniques. The performance of the splitter to take a representative continuous 1/8th subsample of drilling fluid and cuttings by volume was assessed based on its ability to resolve a 1 m interval of low-grade Cu mineralisation (0.74-1.03 wt% Cu) at 398 m that was detected in the reference diamond drill hole. The coiled tubing samples produced an equivalent and unbiased (chemistry and particle-size distribution) subsample, with sub-metre depth accuracy and comparable signal magnitude of the mineralisation at 398 m as detected in the diamond core.

Most fiber-optic torque sensors lack the accuracy to resolve small changes in torque when coupled with thick metal shafts in heavy industry. We present a new type of fiber-optic torque sensor based on the stress-optic effect with a high accuracy and a potentially wide dynamic-range. It is the first interferometric torque sensor based on the 3 x 3 coupler demodulation method, and being an all-fiber sensor head paves the way towards system-level immunity against electromagnetic interference. The optical fibers are located on the external surface of the shaft, which allows numerous possibilities for the internal design. We also studied the feasibility of three temperature-compensation schemes and two signal processing methods for different applications. For the dual-coil configuration, the instantaneous method yields a sensitivity, detection limit and response/recovery times of 6.9 mrad/(N.m), 0.79 N.m, >274 ms and >274 ms, respectively. The cumulative method produces 32.3 mrad/(N.m), 0.08 N.m, >95 s and >274 ms respectively. Torque up to similar to 50 N.m has been tested.

Abstract In November 2016 the Deep Exploration Technologies Cooperative Research Centre (DET CRC) launched the RoXplorer®, a coiled tubing (CT) drilling rig for greenfields mineral exploration, delivering a platform for low-cost, rapid, safe and environmentally-friendly drilling. The launch represented an important technical milestone in the development of CT drilling for mineral exploration and has been complemented by a series of very successful field trials in the first half of 2017 The paper presents CT technology and its application for mineral exploration drilling. The three key challenges for CT drilling in mineral exploration are coil durability, drilling hard rocks with low weight-on-bit and sample fidelity. Results for mineral exploration CT-drilling field-trials in the consolidated cover rocks of South Australia and the unconsolidated cover rocks of the Murray Basin in Victoria are presented and outline how each of these challenges was overcome. The outcomes confirm the promise of this cheaper regional prospecting approach to mineral exploration drilling. The results of assay samples of the CT drilling cuttings are remarkable; the assay samples from the CT drilling at Port Augusta trial matched those of diamond drill core from an adjacent hole.