Minerals Report - International Seabed Authority

of De Beers’ deepwater operation in 1983, developments in this part of De
Beers’ activities took a significant step forward when the organization took
the unprecedented decision to move forward with a test-mining vessel.
He said that it was the work done using this vessel, the Louis Murray,
which helped transform the organization’s work from exploration and
resource development to actual production. He recalled that initially,
some of the types of systems that were used required the equipment to be
suspended over the side of the vessel. He also said that various types of
digging heads were used. These he said, in trying to create coverage
bounced on the seafloor. He said that creating coverage is very difficult to
achieve, and it was very rapidly realized that this was not going to be the
type of system that was going to allow systematic, precise mining of a
deposit. Following on from there, Dr. Corbett said that seafloor crawlers,
track mounted vehicles that could traverse directly on the seafloor were
introduced. According to Dr. Corbett, this configuration required a lot of
work in terms of launching and recovering these systems. He said these
systems were in the region of 40-50 tonnes. He said that the systems that
are currently deployed are closer to 150 tonnes. He emphasized that
hanging this type of technology over the side of a vessel in an offshore
environment with large swells is not a trivial issue. He said that various
types of cutter tests were undertaken, and suction methods tried. He also
said that it was a time of great experimentation and stated that parallels
would unfold as things happen in the deep ocean. He told participants
that one of the early realizations in mining system selection was that they
had to differ according to the geological environment in which these
systems are going to operate.
With another slide depicting a deposit in a very rugged terrain, Dr.
Corbett said that it was this type of deposit that lead to the idea of the
“vertical attack system”. To develop this system, Dr. Corbett said that in
1989, De Beers purchased an oil exploration vessel and converted it to
operate as an offshore diamond-mining vessel (the Coral Sea) for
operations in water depths of up to 200 metres. Dr. Corbett described the
vertical attack system as large-bore drill bits, up to 7 metres in diameter
based on the vessel that is used to drill the diamond deposit. He said that
experience has shown that these systems are very effective for mining in
more rugged terrain, where the ore body is commonly very coarse due to
the incorporation of large slabs of cretaceous and tertiary shelf sandstones
and clay stones. Dr. Corbett said that by April 1991, the vessel had been
transformed quite substantially again in order to be able to contain the ore
that was brought to surface using airlift. He pointed out that the ore
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