Download Poster SubOptic 2013_Ver9.cdr

Submarine telecom cables and the exploration for and
extraction of marine minerals and methane hydrates
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Klaus Michels , Ryan Wopschall , Cornelia Saukel , and Manfred Stender
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Fugro OSAE GmbH, Fahrenheitstr. 7, D-28359 Bremen, Germany
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Fugro Pelagos Inc., 1200 Westlake Avenue North, Suite 803, Seattle, Washington 98109, U.S.A.
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Introduction
The oceans hold large reserves of valuable resources. Placer minerals, oil and
gas, as well as sand and gravel have been extracted from the sea for many years.
Their exploration and exploitation activities were regularly taken into account when
planning new submarine telecom cables. Due to the nature of their occurrence,
and limited by technical capability and cost effectiveness, they were mainly
extracted in nearshore areas and on the shelf. More recently, other marine
resources attracted considerable attention: (1) Polymetallic nodules, cobalt-rich
ferromanganese crusts, and seafloor massive sulphides (SMS) are of interest due
to their metal content; (2) Methane hydrates for their potential importance as a
hydrocarbon fuel; and (3) Phosphorites for their importance for fertiliser
production. The exploration of the occurrence of marine minerals and planning for
their large scale extraction has intensified considerably over the last years.
The exploration and exploitation activities for these marine resources is likely to
increase within the next years and decades. Therefore it is important to take into
account all information available for the planning, routeing and installation for
marine telecommunication cables (see map below) to increase the cable safety
and reliability over its lifetime. This poster presents the information on these
resources, which is available in databases and scientific publications.
Polymetallic Nodules and Cobalt-rich Ferromanganese Crusts
Polymetallic nodules usually occur in water depths deeper than 4,000m, covering
a seabed consisting of unconsolidated sediments, whereas cobalt-rich
ferromanganese crusts exist on the continental slope and along the flanks of
undersea mountain ranges between 1,000 and 3,000m water depths as a layer on
the surface of rock outcrops.
The map on the upper left shows the distribution of known occurrences of
polymetallic nodules and cobalt-rich ferromanganese crusts. They are widespread
but exploration licenses have been awarded only in the eastern Pacific in the area
of the Clarion-Clipperton Fracture Zone (map on upper right) and to a smaller
extent in the Indian Ocean by the International Seabed Authority. In the left part of
the Pacific map some of these areas interfere with the planned cable route of the
Pacific Fibre cable - a project, which has been ceased by August 1, 2012.
Seafloor Massive Sulphides (SMS)
Seafloor massive sulphides are usually
encountered in areas of marine volcanic activity
near the plate boundaries, at water depths of 500
to 4,000m. The map to the left shows the worldwide
distribution of known thermal vents, which are
closely related to the formation of SMS.
The International Seabed Authority (ISA) has
awarded exploration licenses for areas in the
Atlantic (map on right side) and the Indian Ocean.
Two cables - one out-of-service and one in-service
cable - pass through gaps between the license
areas.
Methane Hydrates
Another marine resource, methane hydrates (or
gas hydrates), exists in seabed sediments in water
depth greater than 350m, where the bottom water
temperature is around 2°C. They are seen as a
potentially important future source of hydrocarbon
fuel. Due to their stability field they occur mainly on
continental slopes. The exploration and
exploitation of methane hydrates will probably
happen in a similar configuration to that of oil and
gas reservoirs.
Phosphorites
Phophorites develop in shallow marine environments and on the continental
margin. The map also shows phosphorite deposits on seamounts and islands.
Conclusions
The planning of new cable systems needs to take into account other usages of the
seabed to achieve cable safety and reliability. The extraction of marine natural
resources is an offshore activity with a large potential impact on cables. In the past
most of the offshore exploitation was related to oil and gas as well as sand and
gravel in nearshore settings. Within the last years the extraction of marine minerals
attracted increased attention, especially polymetallic nodules, massive sulphides
and cobalt-rich ferromanganese crusts. The licensed exploration areas are often
far offshore, covering large areas in the Pacific, the Atlantic and the Indian Ocean.
Coordinates are publically available so that these areas can be taken into account
when planning new cable routes. Information on the ocurrence of other marine
resources, e.g. methane hydrates and phosphorites are also publically available.
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GIS databases covering the worldwide occurrence of marine resources provide
the opportunity to identify and mitigate potential conflicts with cable routes at an
early stage. This helps to increase the reliability for the planning process as well as
the safety of the cable during the installation and operation process.
A Memorandum of Understanding between the ICPC and the ISA ensures an
exchange of relevant information on the organisational level.