Looking to tap deep ocean ‘spreading centres’ for clean energy

Geoscience company CGG is hoping to move the needle in generating interest in the intriguing possibility of exploiting the known geothermal energy resources that lie under the world’s oceans.

The initiative is an example of the company’s Beyond the Core strategy of exploring new business opportunities outside its traditional seismic data processing focus.

This has been given extra impetus since the sale of its marine seismic fleet in 2020.

The company says that each volcano setting is different in its magma types, geothermal fluid chemistry and subsurface “plumbing” with temperatures decreasing rapidly away from each geothermal area.

CGG believes the real prize could be exploitation of the potentially substantial geothermal resources residing along the magmatically active, 65,000 square kilometre ocean floor spreading centres, which occur in all of the world’s major oceans.

According to the company, ocean floor spreading centres “offer a more continuous belt of subsurface heat because igneous or dilational tectonic processes, and resulting hydrothermal activity, occur along the full length of each spreading system.

“The magma types and temperatures are quite similar in most of the spreading systems, and the geothermal fluids are relatively consistent and chemically benign — because they are essentially modified seawater.”

World-class potential

The “world-class” geothermal potential of oceanic spreading centres has already been demonstrated in southern Iceland, the white paper authors say, providing a "flying start" to any future developments.

A significant claim for CGG’s offshore geothermal power concept is that it does not necessarily have to be transmitted by cable to shore: the power could be used to electrolyse fresh water from turbine steam condensate to give transportable green hydrogen or ammonia.

A further benefit is that the tools already exist to undertake rapid geophysical mapping of the seabed and subsurface to come up with the most cost-effective pattern of drilling for geothermal energy.

Ability to harness existing extensive oil industry offshore technology, particularly in deep water where much of this energy source will be found, is another plus.

With the white paper, CGG seems to have pre-empted competition in pitching a business and operational framework for future offshore geothermal exploitation.

In 2022, the company registered a patent covering a combination of geological, geophysical, and engineering technologies to support research into exploration, development and monitoring of offshore geothermal resources.

Peter Whiting, executive vice president, geoscience at CGG, says: “The opportunity offshore geothermal resources presents could be a game-changer in supporting the United Nations Development Programme’s 2023 Sustainable Development Goals including clean energy, climate action, and partnerships for sustainable development.

“While the patent application recognises the exceptional work of our geothermal experts, our motivation for seeking it is to ensure that there can be rapid, responsible, and equitable development of these resources.”

CGG’s recent credentials in the geothermal field include the launch in March 2022 of its multiclient Global Geothermal Resource Assessment study, part of its GeoVerse geological offering that delivers diverse geoscience data sets for multiple industries.

This draws upon the company’s well, seismic and interpretation database as well as experience in over 130 completed onshore geothermal projects applying a proprietary methodology to evaluate over 700,000 subsurface temperature data points.

High-energy volcanic geothermal systems — as well as lower-temperature but far more extensive systems associated with sedimentary basins — were studied, the latter representing a significant emerging resource opportunity.

Agency request

Tentative interest in offshore geothermal is reflected in the request in 2022 by the Secretariat of the International Seabed Authority (ISA), a regulatory body established by the United Nations, for consultancy service proposals to assess the geothermal energy potential for sustainable development of seabed hydrothermal systems in “the Area”, which it defines as the seabed, ocean floor, and subsoil beyond the limits of national jurisdiction.

The consultancy would support the ISA Secretariat in assessing the energy generation potential of hydrothermal vent sites in mid-ocean ridges and the review of technological solutions for the sustainable development, the protection and the monitoring of volcanic-hydrothermal monitoring in the Area. The outcome of ISA’s call for proposals has not been published.

In its long list of recommendations for exploitation of offshore geothermal energy, CGG acknowledges the need to work with the ISA. In recent years the agency has been mainly preoccupied dealing with commercial pressure to regulate and licence mining of valuable seabed minerals in international waters, a highly sensitive political and environmental issue.

In fact, the first geothermal projects along the lines outlined by CGG are most likely to take place in locations where national jurisdiction applies, for example Iceland, the Gulf of California and possibly the Red Sea, where geological conditions are favourable.

However promising CGG’s concept may be, the reality is that the development of geothermal power on land, let alone the deep ocean, to help meet net zero carbon emissions by 2050 goals still lacks momentum.

Geothermal still only accounts for a mere 0.5% of renewables-based installed capacity for electricity generation, heating and cooling, globally, according to the International Renewable Energy Agency.