Obiettivo By tapping the latera geothermal field to produce electricity for a 5 Mw generator. Two exploratory boreholes (L1-L2) proved the existence of a productive reservoir:- steam at 60 t/h - 150 deg C and water at 250 m3/h at 100 deg C. Stage 1 covers the drilling and testing of two production wells between 1,500 and 2,000 m.The wells are located in the central part of a carbonaceous formation uplifted (Tuscan series). The expected geothermal gradient is 2,7 deg C/10 m.- Stage II: if the results are positive, two injection wells will be drilled.- Stage III: this will include the installation and testing of the 5 Mw power plant.The total annual projected energy saving at the end of the project is 15,000 TOE.Drilling of wells L3 and L3D verified data obtained from wells L1 and L2 regarding the temperature regime of the caldera and trend of the buried carbonate structure.Highest temperature gradient value for all Latera zones was recorded at 2,95 deg C/10 m.Due to lack of permeability in the mesozoic carbonate of the folded structure, well L3 is unproductive. Well L3D (side tracked hole in L3) is highly productive due to fractured layers between 530 and 1,370 m. The proved flow-rate of 600 t/h at 13 Bar and 185 deg C was sufficient to justify initiating the second stage of the project.The first production well, (L3) was drilled between April and August 1980 to a final depth of 2,485 m. Partly modified limestone and marl (Lias-Trias) was encountered beneath a cover of volcanic strata between 510 and 1,560 m. Rock clays and marls were encountered between 1,560 and 2,300 m, followed by metamorphic formation below 2,300 m. Relatively permeable limestones were traversed between 950 and 1,435. Production is limited to 30 m3/h at a 50 kg/cm2 pressure loss. After injecting water and acid, a reinjection flow-rate of 150 m3/h at 37 bars was obtained. An inversion of the geothermal gradient between 1,000 and 1,700 m suggests the presence of a reservoir close by. With the Commission's agreement, the contractor decided to start directional drilling from the same L3D site instead of going ahead with the planned second production well (L4). This was completed between June and September 1981.Structural and tectonic factors suggested drilling in the direction of N60E. A 13 3/8" casing was sunk to 520 m drilling continued down to 1,369 m (12 1/4" open hole) through limestone strata, without returns and with several blowouts occurring. One of these - at the reservoir level of around 1,300 m - was spontaneous. Distance between L3D and L3 at 1,300 is 335 m. Drilling continued down to 1,369 m (12 1/4" open hole) through limestone strata, without returns and with several blowouts occuring. Lithological section similar, i.e. Quaternary volcanic strata down to 520 m; Lias limestone from 520 m to 765 m and Upper Lias Limestone from 765 m to 1,369 m. A series of tests (production and reinjection) has been conducted. Principal characteristics revealed by the most recent at 120 t/h (20 % steam, limited by the separator): well-head temperature and pressure - 198 deg C at 18 bars salinity - 20 g/l; temperature at the bottom of the hole - 225 deg C; enthalpy - 231 kcal/kg (pressure loss: 6 bars). It is reasonable to expect a maximun stabilized flow-rate of approximately 600 t/h at 13 bars and 185 deg C without tubing between 520 and 1,369 m, and with 1,5% CO2/HO2 by weight. Drilling of wells L3 and L3D was completed in September 1981. Programma(i) ENG-ENALT 1C - Programme (EEC) of financial support for projects to exploit alternative energy sources, 1979-1984 Argomento(i) 2.1 - ELECTRICITY GENERATION Invito a presentare proposte Data not available Meccanismo di finanziamento DEM - Demonstration contracts Coordinatore ENEL SPA Contributo UE Nessun dato Indirizzo Viale Regina Margherita, 137 00198 ROMA Italia Mostra sulla mappa Costo totale Nessun dato
