Post by Marco Panebianco

Geothermal energy for Galliate (NO), Italy and surrounding municipalities from Eni depleated wells The first from the left is the scheme that can be applied to use the Eni depleated wells in Galliate (NO), Italy and surrounding municipalities to recover thermal energy for electricity production and district heating. According to a recent public meeting well-organized by the municipal administration in Galliate (NO), there would be the opportunity of using Eni's depleated oil wells, now exhausted in terms of oil content, but not hot water production with 98-99% water cut, to produce electricity and hot water for district heating. The first official proposal we can outline, having previously worked on this project for Eni, dates back to a presentation given at the World Geothermal Congress in Melbourne, Australia in April 2015 by Elena Soldo and Claudio Alimonti of La Sapienza University of Rome. The project has been revisited and abandoned several times due to various problems that we have analyzed and attempted to mitigate, but it remains essentially feasible, with the necessary recalculation of the return on investment to be verified again. Oil extraction wells, now in very small percentages compared to the content of the produced water (98-99% water cut) already exist, including also those for reinjecting the produced water, because the extraction principle was based on bringing the oil to the surface, separating the water, and reinjecting the separated water to sustain the reservoir pressure. The principle can be continued according to the scheme, as already mentioned above. The produced water, along with the small amount of oil, reaches the surface at an average temperature of 160°C, which would evaporate a special fluid, usually a diathermic oil such as cyclopentane. It is then expanded in a turbine connected to a power generator, similar to a steam cycle. It is then cooled by an exchanger connected to a district heating circuit, before returning to a closed cycle and evaporating again. We call this system ORC Organic Rankine Cycle wellknow in the energy recovery industry. With a significant number of wells available—three only in Galliate—with appropriate workover of the various levels of production, this heat recovery activity could be optimized for the purposes mentioned. The potential for this type of geothermal energy in Italy is estimated at 20-40 GW not only from depleated wells, but include dedicated new wells.