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Polymetallic nodule resource survey boosted for DeepGreen

DeepGreen had recently commissioned a baseline vessel-mounted multibeam survey across their NORI D mineral property in the Eastern Pacific. Although they needed to understand the water depth across the entire area, the resolution of the recent survey was not good enough for the development of the mineral resource so DeepGreen approached Fugro for a near-seafloor ultra high resolution geophysical survey on the property with decimetre-scale resolution in selected areas.

Challenge

DeepGreen knew from early exploration efforts in the 1970s that polymetallic nodules rich in nickel, copper, and cobalt were abundant on the seafloor across their NORI D mineral property in the Eastern Pacific. Development of the green-tech minerals on the property could support increasing demand for batteries and electric vehicle production.

They had recently commissioned baseline vessel-mounted multibeam surveys to establish the water depth and topography, and took samples to help understand the distribution of the ‘inferred resource’. However, the resolution of the recent surveys was not good enough for the development of the mineral resource, specifically they needed detailed seafloor measurements for a nodule collector vehicle test, so DeepGreen approached Fugro for a near-seafloor ultra high resolution geophysical survey on the property with decimetre-scale resolution.

Solution

Fugro proposed accomplishing more with this campaign and, together with experts from DeepGreen, designed a survey campaign to determine a good collector test site but also improve the resource classification according to the international mining codes. A team of Fugro’s seafloor mapping experts and marine geologists were added to the survey crew to:

  • Process and interpret multiterabytes of seafloor camera imagery taken from a    4200 m water depth, including from Fugro automatic nodule detection software
  • Collect a blind grid of nodule samples from predetermined points supported by photographic and ultra high resolution geophysical data that could be correlated post-collection for resource estimates
  • Catalogue the recovered nodules and document the physical properties (size, shape, density) and prepare samples for onshore geochemical analysis

To minimise vessel days, we deployed a grid of seafloor transponders so that our Fugro Echosurveyor VII autonomous underwater vehicle (AUV) could acquire precision data while the vessel collected nodule samples from other parts of the property.

Surface layer trays filled with nodules 

Our ability to more accurately estimate mineral resources for the NORI project represents an important milestone in our commitment to bring clean metals to market.

Gerard Barron, CEO, DeepGreen Metals

Innovative highlight

This was the world’s first engineering-level AUV survey executed in simultaneous operations with a precision mineral-sampling programme at these water depths. The valuable vessel days that we saved allowed for the inclusion of a robust mineral-sampling programme.

Because critical decisions were needed in situ, Fugro developed automatic nodule detection routines to assist with interpreting the data in the field prior to the survey. In consultation with DeepGreen, we also designed nodule sampling and processing protocols to support the stringent resource assessment requirements.

Surveying seafloor material 

Impact

Our innovations allowed us to deliver significantly more than DeepGreen’s original scope:

  • The collector test site was geologically and geotechnically profiled to benchmark future sampling and recovery efficiencies
  • Seafloor photographic imagery and geophysical data were collected for environmental monitoring sites, particularly for metocean studies
  • Environmental baseline reference zones with habitats similar in character to the collector test site were documented with detailed photographic imagery
  • Soil properties and behaviour were determined from field tests and onshore analysis at our Houston geotechnical laboratory

Most importantly this work demonstrated an efficient and cost-effective nodule resource estimation methodology that resulted in a 51 % increase in the known resource tonnage at the NORI D site.

  • Client

  • Nauru Ocean Resources Inc., a wholly owned subsidiary of DeepGreen Metals
  • Regions

  • North America
  • Location

  • International waters in the Eastern Pacific Clarion-Clipperton Zone (CCZ)
  • Project Duration

  • April 2018 - June 2018
  • Industries

4200 m

Depth of mineral resources in the ocean

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