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Zawartość zarchiwizowana w dniu 2022-12-27

DRILLING OF FOUR GEOTHERMAL WELLS IN S MIGUEL ISLAND (AZORES) FOR ELECTRICITY GENERATION

Cel

The global aim of the Geothermal Project of S. Miguel is the production of electricity, using the geothermal resources of the island.
With this project (drilling of one geothermal well) it will be available at least 1/4 of the geothermal fluids necessary to justify a power plant with 13 MW gross.
According to the long-term test performed under the supervision of CFG-Compagnie Francaise pour le Developpement de la Geothermie et des Energies Nouvelles, the main results achieved with the well CL2 are as follows :
Well CL2 produces about 150 tons/hr maximum through a 6" lip-pipe. The enthalpy is 1000 kJ/kg which corresponds to a reservoir temperature of 232 deg. C. It produces from two zones, the upper one between 700 m and 800 m depths, and the lower one below 1150 m depth. It is not certain that the upper zone is two phases as it is the case for well CL1, but it is not impossible since the lower zone is colder and could cool the produced mixture.
The calculated permeability thickness is 8.6 Dm which is considerable higher than for well CL1. Only one pressure transient test was performed in CL2 and the well stabilizes very quickly. This one test could therefore be misleading, but is is likely that CL2 has a higher value than CL1. It was not possible to calculate the skin fromthe data obtained.
The chemical measurements performed on CL2 brine and steam during the test show that well CL2 is very similar to well CL1 on a chemical point of view.
The collaboration between CFG and The University of the Azores regarding the chemistry of the geothermal fluid allows to conclude:
- The total dissolved salts are slightly higher than in CL1 but the main cations and anions are the same.
- The evolution of the parameters monitored during the deliverability test allows us to assume that the CL2 is producing from two zones as mentioned before. The lower aquifer which is colder and may be more mineralized seems to contribute in higher proportions to the T.D. for higher flow rate. The silica evolution agrees with this model.
- A better knowledge of the chemical composition of each aquifer and of the mixing model could only be obtain through down hole sampling that could not be performed during this test because of a material failure. Unfortunately gas analysis resultsare not available yet but we can presume that CL2 gas fraction is very close to CL1 gas with CO2 dominant phase (at least 99%).
- For equilibrium and scaling risk calculations we assumed that the total fluid (brine with gas) was in equilibrium in down hole conditions with calcite.
- The geothermometers calculations applied to silica and alcali ions are in good agreement with down hole measurements (232 deg. C in average).
On average a classic condensate steam turbines uses 8-10 tons/hr per produced MWe. For WHP of 10 bar the steam production from well CL2 should be around 30 tons/hr which gives maximum 3 MWe single well production.
The global project consists of drilling of four geothermal wells, with the correspondent geophysical logging and reservoir engineering, and the building of the power plants for 13 MW gross.
This particular project consists of drilling one well (one has already been drilled, successfully) with a depth of 1400 meters approximately; 9 mts of surface casing with 30", 111,63 mts of anchor casing with 20", 297,1 mts of conductor casing with 13" 3/8, 577,4 mts of production casing with 9" 5/8, and 816,05 mts of slotted liner with 7".

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Koordynator

SOCIEDADE GEOTERMICA DOS ACORES (SOGEO)
Wkład UE
Brak danych
Adres
AV. INFANTE D. HENRIQUE 33, 3 DTO
9500 Ponta Delgada
Portugalia

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