Increasing resource efficiency through Sonic Drilling


Subsurface ore deposits (up to about 50 m depths), such as Nickel laterites and Aluminium-rich bauxites, placer diamond and gold deposits in tropical and permafrost regions, are heterogeneous at orebody scale. This is related to mixtures of loose and solid, soft and hard materials of variable grain sizes leading to contrasting physical properties.

Conventional drilling is often impossible or does not reach complete and coherent sampling. Sonic drilling (Eijkelkamp SonicSampDrill) with specially developed core shoes and rigs for these environments achieves coherent drill cores with over 95 % recovery rates in a short time (e.g. permafrost region: 25 holes of about 11 m in 2.5 days). For example, in a Siberian subsurface alluvia l gold deposit close to Magadan, the LargeRotoSonic crawler was able to sample clay layers hosting fine gold and gold dust. This finding contributed to a significant increase of the Au reserves. In alluvial diamond deposits in NE Angola, thanks to the CRS-V CompactRotoSonic crawler equipped with the AquaLock piston sampler high grade alluvial channels could be targeted and significantly helped to increase diamond production and extend Life of Mine.

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This technology provides undisturbed cores in a short time span (≈50m/day) with low failure rate and little waste.

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In order to increase natural resource efficiency such as metals and diamonds from subsurface deposits, rapid, reliable drilling methods leading to high quality sampling with improved logistics, reducing water consumption and minimized waste are needed.

Efficient exploration, mining and processing relies on optimized geomodels. The smart definition of mineralogical, chemical and geotechnical key parameters is based on geometallurgical studies. These parameters compromise optimal ore and metal recovery, low (to zero) waste, low environmental impact, low energy/time consumption during beneficiation and saleable products.

High quality drill cores are indispensable to perform systematic sampling for statistical mineralogical and chemical studies, interpretation, geomodeling and decision making during exploration campaigns, process design development or optimization. The systematic logging of drill cores is actually more and more driven by on-line-on-mine-real-time analyses. Therefore, cost-intensive drilling must bring out high recovery rates, coherent undisturbed and complete cores to obtain reliable data being used for resource and reserve estimates, and metallurgical test work.

Conventional diamond drilling methods are time, cost and water intensive. Sub-surface ore deposits, such as Ni (Co-Sc) laterites, bauxites, alluvial gold, diamond, titanium oxides, zirconium are difficult (or impossible) to drill presenting low core recovery rates and/or partial drill core destruction. These terrains are heterogeneous in grain size, partly loose, and highly variable at vertical and horizontal scale. Fine grain size sediments such as clays are often lost, but can host e.g. economic gold. This leads to erroneous models and decision making.

Sonic drilling meets the highest technological standards and is more and more used for complex sub-surface ores, as this technology provides undisturbed cores in a short time span (≈50m/day) with low failure rate and little waste.

Four successful case studies from subsurface ore deposits in arctic, desert and tropical climates, are presented in the context of the main problems related to drilling in sub-surface ore deposits.