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Installed geothermal generating capacity (December 2004) in MW

 

The only operational field in Costa Rica is Miravalles, a water dominated reservoir of approximately 20 km² at a depth of 1,000-2,000 m and 240°C (Mainieri et al., 1995). The first unit started its operative life on 1994 (single flash, 55 MW) followed by a small 5 MW well-head back-pressure unit and a second single flash 55 unit (Miravalles II) in 1998. In 2000 Miravalles III (single flash 29.5 MW) and in 2003 the binary unit Miravalles V (18 MW) completed the total installed generating capacity in the field up to a total of 162.5 MW. The total electricity generated in 2003 was 1,145 GWh/yr (Mainieri, 2005; Mainieri, 2003). The field uses 52 deep wells (32 production, the remainder for gravity reinjection).

 

At present the geothermal installed power contributes 8.4% of the country’s total electrical capacity and 15.1% of the produced electricity. The total number of wells drilled in the country is 131, with a total depth of 124 km.

 

A further eastward expansion of the field is foreseen: the recent well PGM-55 at 1.5 km from the exploited field identified a new high permeability area, hydraulically connected with the present reservoir and with a potential of 4 MW. Future exploitation of this area will require directional drilling for environmental protection, since it is located near a protected natural area (virgin rain forest). It will be the first experience in the country of multiple wells from the same drilling pad.

 

Geothermal energy is the second most important contribution to electricity generation: its economic relevance is highly strategic in the country, due to the great dependence of thermal plant on imported oil: despite of the installed capacity of 17%, their contribution to electricity production is only 2%. Due to the presence of such important geothermal resources, it is possible to operate fossil fired plants as reserve units.

 

In the northern part of the country, near the Nicaraguan border, the second geothermal area of the country (Rincón de la Vieja Volcano) will be exploited in the coming years. On the southern slope of the volcano, the Las Pailas field has been explored with 5 wells in 2001-2002. 18 MW has been proved from a 250°C reservoir, with a possible expansion up to 35 MW. On the northwestern slope, in the Borinquen field, the first of four planned exploratory wells is under construction. Preliminary results confirm the presence of an important thermal anomaly.

 

Taken from Ruggero Bertani’s paper, " World Geothermal Generation 2001-2005: State of the Art", published in Proceedings of the World Geothermal Congress 2005, Antalya, Turkey, 24-29 April 2005.