Portugal
Mainland
Azores
In
Portugal geohydrological studies have increased considerably in the last two decades.
Some of the projects have already passed the feasibility phase.
In the Portuguese mainland, there are about fifty natural low enthalpy geothermal
occurrences spread all over the country. Temperatures range from 20°C to 76°C,
however, most of these occurrences have temperatures between 20°C and 40°C. Their
geographical distribution is not uniform throughout the country. The most important
geothermal occurrences are located in the northern part of Portuguese mainland.
Most of the thermal waters flow in the Pre-Mesozoic Hesperic
Massif associated with granitic and schistose rocks and are related to local and
regional fault systems. The thermal occurrences issuing in the Western and Southern
Sedimentary Borders display lower temperatures but have higher water flows and
total dissolved solids than those from the Hesperic Massif (Carvalho, 1998).
In
the Azores islands a large number of active volcanic manifestations are well known,
justifying the considerable rise in geothermal investigations. The program on
São Miguel Island has resulted in a pilot geothermal generator plant producing
20-25% of the island requirement (Bicudo da Ponte, 1998).
Average temperature
of the reservoir is 240ºC at 1200 m and the well-head temperature is about 200ºC
(Carvalho, 1998).
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