Preliminary Assessment of Offshore Geothermal Resource Potential of Portugal - The Case of Azorean Deep-Sea Hydrothermal Vents

摘要

Hydrothermal vents are submarine hot springs and geysers that originate in volcanically active areas often at mid-ocean ridges, where the planet tectonic plates are spreading apart and magma wells up to or close to the surface of the seafloor. Hydrothermal circulation at the deep ocean ridges is an essential complex process regulating mass and energy transfer from the interior of the Earth through the oceanic lithosphere, to the hydrosphere and the atmosphere. Hydrothermal venting has long been recognised to provide significant fluxes of both heat and chemicals to the deep ocean. Hydrothermal fluids are generally with high heat flows and dissolved minerals, making them an excellent target for exploitation of hydrothermal energy and mineral resources. The energy extraction from the hydrothermal vents could provide a carbon-free and sustainable source of energy for the future generations. A substantial number of hydrothermal fields are located in the vicinity of the Azorean archipelago (Portugal) comprising high-temperature fluids under supercritical conditions. The hydrothermal vents of the Azores are a chain of vents that are fragments of the Mid-Atlantic Ridge. These geological structures, developed from masses of basalt, are of a geomorphological interest, in addition to being a rich ecosystem of diverse subaquatic plant and animal life. Although challenges and barriers exist in exploring mid-ocean ridge hydrothermal vents, these resources remain to be one of the most potential and stable sources of renewable energy. The study at hand presents a preliminary assessment of geothermal resource potential of the Azorean hydrothermal vents using a modified version of the volumetric stored-heat assessment method developed by the United States Geological Society (USGS) (1979) and the energy balance method presented by G.Hiriart (2010). The further part of the study aims at using the obtained data to assess the technological and economic potential of energy extraction from the hydrothermal vents.