The existence of fumaroles and hot springs, active volcanism and historic hydrothermal craters have made Nisyros one of the prime targets for hydrothermal research conducted in the 1970s by IGME – Institute of Geology and Mineral Exploration (initially) and PPC – Public Power Corporation (at a subsequent stage).
All research projects indicated the presence of a geothermal reservoir developing high temperature at a relatively moderate depth. In the 1981-1982 period, PPC performed two deep boreholes for exploration – exploitation purposes, at the Lakki site, inside the Nisyros caldera. The first (Ν1 – 1810m maximum depth) found a hydrothermal reservoir of very high temperature (> 450 oC), extreme pressures and fluids of very high salinity after 1400 meters. September 1981 demonstrated the current dynamic status of the Nisyros volcano with the ‘adventure’ of the first production test at Ν1 borehole. The geothermal fluid produced took barely a few minutes to surpass 45 atmospheres pressure, exceed the temperature limit of the present equipment (400°C) and it took the introduction of 40,000 liters of seawater in half an hour under 75 atmospheres pressure to regulate the situation. During the 6-hr period when the borehole was in operation, the geothermal fluid deposited over 120 tons of sulphuric and chlorine salts. Thus, Nisyros is demonstrably the most dynamic and hottest explored geothermal field of the world in a plate collision environment, due to the presence of an extremely hot magma chamber at shallow depths.
The second deep borehole (Ν2 –1543m maximum depth) encountered the high-temperature hydrothermal reservoir at a shallower depth (1000-1400m). Fluids and pressures were less problematic. Production tests permitted the assessment that the field can produce electric power at a 2 Mwe capacity.
The local population resisted the further utilization of geothermal power, their attitude mainly owed to miscalculated decisions and poor management of the Milos geothermal field by PPC. Hence, research & development work ceased for the Nisyros field. The available data indicate that this field could easily produce around 20 ΜWe.
In addition to high – temperature fluids, the site is abundant in low – temperature fluids (45-75 centigrade, perhaps even higher at 95 οC). These pose minimal or no problems with respect to tracking, extraction, utilization and disposal, and they can cover a multitude of applications (desalination, health tourism, all kinds of farming, cooling & heating etc). Furthermore, medium – temperature fluids (120-140 degrees) present in relatively shallow reservoirs (<1200 m.) encumbered with significantly less problems than high – temperature reservoirs,can be exploited for electrical power generation purposes by limited size, low – disturbance plants.
