Under water chimney sampling

Deep sea mining exposed

Zinc, copper, silver and gold await the deep sea miners.

'In the depths of the ocean, there are mines of zinc, iron, silver and gold that would be quite easy to exploit,' said Captain Nemo, hero of Jules Verne's 'Twenty Thousand Leagues Under the Sea' (1870). But now the 19th century fiction is drawing ever closer to a 21st century reality as the technological barriers are gradually being overcome.

Huge deposits of zinc, copper, silver and gold are indeed lying in wait on the seabed, formed by seafloor massive sulphides (SMS), or black smokers. Using designs borrowed from the oil and gas, trenching, and deep water cable-laying industries, several companies are close to mining the depths.

The race to the seabed is being led by two companies, Nautilus Minerals with a project off Papua New Guinea (PNG), and Neptune Minerals in the seas off New Zealand. Both are deep into an exploration stage, and expect to start extracting minerals within five years.

Nautilus is proposing to develop the Solwara 1 SMS system in the territorial waters of PNG. When it comes online, the project will be the first full-scale deep water mineral extraction project in the world. Solwara 1, a high grade copper-gold resource, lies in 1,600m of water.

Nautilus' proposed mining system will consist of an excavator, a support ship, and a riser and lifting system to pump metal sulphide debris to the surface. Soil Machine Dynamics (SMD), based in Newcastle, UK, received the £33m contract to design and build Nautilus' digging tool, which will incorporate the most technically difficult component - the cutting head. High-pressure underwater drilling tests using sulphide samples from Solwara 1 are being carried out at SMD to determine the best design for the cutting head and the pump that will suck the materials to the surface. This type of excavation has been dubbed 'surgical mining'.

'As the material is broken up it is sucked up with an enormous amount of seawater to the deck of the ship,' Stephen Rogers, chief executive officer of Nautilus Minerals, explains. 'The water is then filtered and cleaned in a dewatering system, and the cold seawater is put back down at depth. So, unlike in dredging, discharge water goes back where it came from. There will be no ugly plume of mud coming out of the back of the ship.'

The system, called 'Seafloor Resource Production System', is actually multiple devices, so three different tools will be used in the production operation itself. 'They will move around on the seafloor, cutting the material and gathering it up ready for lifting to the surface,' Rogers adds. 'Those machines are based on trenching vehicles that are used in the oil and gas industry to cut ditches in the seafloor for pipeline.'

At present, the oil and gas industry is experimenting with seafloor processing that saves the expense of pumping huge amounts of water and sand to the surface for separation, only to have to pump it back to the seabed after extracting the oil. The Nautilus approach is to use tried and tested methods. 'The material is disaggregated on the seafloor, and is basically vacuumed up using water pumps, which draw the water in at such a velocity that it picks the disaggregated material up,' Rogers explains.

'It then pulls a slurry, with about 10-12 per cent solid to 90 per cent liquid, or sea water, and that is then pumped up to the surface to a vessel where the water is then separated from the solid, which is transferred on-shore for treatment.'

Nautilus are considering all types of vessels but the function would fit perfectly for a heavy construction class of ship.

Deep water cost

On the face of it, the high cost of working in deep water would appear to make any venture to mine the minerals prohibitively expensive. But the high cost of farming the metals is offset by the relative ease of extracting the ore - it lays on the surface so no drilling is required, and the richness of the deposits - far surpassing anything you could expect to find on land.

'We believe the scale of the operation is such that we can do it economically, and what distinguishes the SMS systems that we are looking to mine on the seafloor is that they have very high-grade copper and gold,' Rogers says. 'We are looking at copper concentrations of around 10 per cent, whereas a normal land-based, terrestrial-based, mining operation project generally has copper concentrations of around 0.5-1 per cent. The combination of high metal content and the scale of the operations that we are launching make it an economic proposition.

'In addition to this, all of these SMS systems actually form on the surface of the seafloor. This is another significant advantage over land-based mining, in that we don't have to cut and recover a lot of material from the seafloor before we get to the mineral rich material, as it is literally sitting there as a soft rock that we can cut and remove immediately.'

The Solwara plot

Lying in 1,600m of water, the Solwara plot is deep, but in terms of oil and gas exploration experience it is comfortable. There are a host of oil operations going on at depths of 3,000m with some drilling operations even pushing the 4,500m barrier.

The project is still in the exploration phase, but with the contract placed for the digging tool they are well advanced in the development activities before moving into production.

The operation commenced with a geochemical and high-resolution bathymetric type survey. 'We were looking for anomalies on the seabed and we use geochemical techniques to essentially sniff metal content in the water,' Rogers says.

'Once we have been through that initial process, we use ROVs [remotely operated underwater vehicles]. We use visual identification and electromagnetic techniques and we take surface samples using the ROVs. Then the third stage of the exploration programme is to conduct drilling operations on the seafloor, and we basically drill into the seafloor taking core, and then use that core to do metallurgical testing and so on.'

On the subject of mining rights, all the areas that both Neptune and Nautilus are operating in today are either within the territorial waters or the economic enterprise zones of specific countries. So the mining leases are granted by those countries in the same way the leases are granted for oil and gas companies in oil and gas drilling projects. It is a two stage process. Initially it is an exploration licence, which allows the companies to explore on that particular block and then when it is time to develop they will have to apply for a mining lease, or a mining permit, under which they can conduct the physical mining production operation.

The exploration phase is coming to a close and Nautilus hope to start extracting minerals at production volumes in 2013.

'We are working towards moving onto production, and a time-scale has been declared,' Rogers says. 'We published an engineering and cost study about two months ago and in there is quite a lot of detail about our plan.

'The programme to go into production would take us about 27-30 months from the time we initiate the building of the equipment. Right now we are still in the engineering programme and looking to bring in funding to allow us to start to build the equipment. We are already committed to the build of the seafloor mining tool, or seafloor production tools, as we call them.

Challenges

Despite appearing to push technological boundaries, the project is based on well proven procedures, albeit drawn together for the first time from a variety of other sectors. So the major stumbling blocks, if there are to be any, would appear to come from the funding and environmental arenas.

'I think we have all of the same challenges that any deep-water project faces,' Rogers says. 'The differences that we have are that we have chosen a location in PNG that is protected on three sides by islands, and it is a relatively benign environment with excellent environmental conditions.

'We are operating about three degrees below the equator so we are not prone to any heavy cyclonic action and, in fact, enjoy fantastic weather. So we don't have significant environmental challenges to worry about on this first project. We are taking existing technology as far as we possibly can and adapting those to this new application. So we're not really using anything new. It is all existing technologies, but just adapting them for a new application.

'The seafloor cutting operations - we are modelling that on the trenching equipment used in the oil and gas industry, and we are matching that up with cutting technologies used in the land-based mining industry.

'The pumping systems and the riser systems that we are using are conventional production systems used in the oil and gas industry, so the riser is a conventional production riser used in the oil and gas industry.

'The vessel is also a conventional vessel seen in the oil and gas industry. The watering plant used to strip the water out from the ore is conventional mining technology.'

Environment

No operation of this scale can ever get close to fruition without engaging the attention of environmental groups.

Nautilus have complied with all the environmental legislation including a thorough permitting system and have passed by adopting what Rogers calls an open and transparent policy to what they are doing. 'We're not embarrassed by anything that we have done, as I say we have taken a transparent approach,' he says. 'We have brought in around 14 or 15 scientific research groups to work with us in the collection of data and the evaluation of that data. Those scientific bodies work with us to help develop out mitigation strategies from an environmental impact point of view.

'We are working at 1,600m water depth, which is well below the areas that fishing is regularly undertaken. We are 40 or 50km away from the nearest reef and we are attempting to minimise the environmental impact with everything that we are doing.'

While Rogers is content with his ticks on the environmental check list, there are others who are beginning to raise concerns about the prospect of giant vehicles dredging the seabed. One such doubter is Cindy Lee Van Dover, of the School of the Environment at Duke University. 'Mining of seafloor massive sulphides, where permitted, will be a frontier use of the deep sea, with no precedent for how to monitor, regulate, and minimise habitat loss and degradation or to facilitate mitigation and restoration,' she says.

'Lessons learned and best management practices from activities that degrade or eliminate habitats on land, in coastal waters, and elsewhere in the deep sea should be applied to seafloor massive sulphide systems, but new practices will undoubtedly need to be developed as well.

'Scientific research can help to clarify complex risks, identify gaps in knowledge and provide an early warning of unexpected or unacceptable consequences. Given that mining may take place in the deep sea, it is imperative that scientific research is undertaken in a proactive manner to allow us to propose strategies that minimise risks to biodiversity and ecosystem function in areas targeted for mining activities.'

Those doubts will need to be assuaged as the project, and others like it around the world, move into production, but one thing is for certain - we are entering a new age for mineral extraction.

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