Objetivo The aim of the project is to demonstrate the use of geothermal water to provide 50% of the heating requirements for the equivalent of 1600 offices and domestic dwellings in the ENI urban district south of Milan, using both direct thermal exchange and heat pumps. Expected savings of 1,500 TOE/y are predicted.The reservoir - a clastic Miocene formation - is to be exploited by use of two deviated wells to obtain a 1000 m spacing between the production and injection well at the top of the reservoir.At a depth of 1,900-2,000 m flow is estimated at 180 m3/h, salinity 20-70 g/l and the well head temperature 65 deg C.Untreated water will be injected at 50 deg C.Geothermal water production is less than expected, due to low reservoir permeability in relation to the heterogenous lithology and clay content of upper Miocene clastic deposits. Notwithstanding the complex geometrical features of the reservoir, injection was successfully carried out.Total exploitable flow is 50 m3/h at 62 deg C and 70 g/l salinity. Required power to flow and inject is 250 kW. Annual energy saving will be 800 TOE, inclusive of gas contribution.Operation payback is too long from economical point of view but this doublet represents an experimental project to gather information on production/injection in thin multi-pay sandy formations and overcome injection problems.From a number of technical aspects the system behaved satisfactorily whilst some problems have been encountered.On the positive side the reservoir behaved as expected; no substantial corrosion was encountered; seismic monitoring detected no events connected to injection; however there were some problems relative to scaling and fine particles in the well and the surface equipment, even if the filters behaved satisfactorily.The first well (M1) was drilled to a final depth of a 2,505 m in 1979 and the second (M2) in 1981 to a final vertical depth of 2,276 m (directional depth : 2,717 m). The wells were completed with 9 5/8" and 7" casing which were cemented and then perforated. The following target formations (Miocene) were encountered : Colombacci (1,968-2,229m) comprising gravels, sands and marls; Sergnano (2,299-2,250) comprising conglomerates with clays and sands; Gallare (2,250-2,505) comprising marls, silts and clays. The characteristics of well M1 are : productive levels between 2,423 and 1,967 m; bottom hole temperature 69 deg C; salinity 70 g/l and methane gas 2 Nm3/m3 H2O.Characteristics after acidizing are : transmissivity 1,84 D x m; net pay 10-19 m and possible flowrate, assisted by submerged pump, 50 m3/h for a drawdown of 400 m. The skin (estimated at -1 to -2) seems to prove that the aquifer is undamaged.Characteristics of well M2 (horizontal spacing in the aquifer : 1.100 m from M1)are : productive levels between 1,922 and 2,259 m (vertical); bottom hole temperature 68,5 deg C; possible flowrate (with submerged pump) 60 m3/h, after acidizing. Lithology similar to M1 but 50 m higher. As M2 was better situated from the structural point of view, it was decided to use this well for production. A Reda pump was installed at 935 m with a cross-over valve at 945 m, this being necessary because of the large quantity of gas present. Well M1 was equipped for injection by installing a 5" tubing with a paker anchored to the 7" casing at the 2,020 m mark, thereby permitting reinjection at a rate of 30 m3/h through the anulus at the upper levels (1967-2,010 m) and at a rate of 20 m3/h through the 5" tubing between 2,034 m and the bottom of the well. Long term tests were carried out in June 1982 at the operating flowrate of 50 m3/h and at 62 deg C well head temperature with M2 as the production well and M1 for reinjection. The fluid was reinjected at around 25 deg C and 80kg/cm2; 100 Nm3/h of a natural gas were separated from the water. Programa(s) ENG-ENALT 1C - Programme (EEC) of financial support for projects to exploit alternative energy sources, 1979-1984 Tema(s) 2.2 - HEATING Convocatoria de propuestas Data not available Régimen de financiación DEM - Demonstration contracts Coordinador ENI SpA- AGIP Aportación de la UE Sin datos Dirección VIA EMILIA 1 20097 S. Donato Milanese (MILANO) Italia Ver en el mapa Coste total Sin datos
