| Abstract |
Ecuador is located on the active convergent plate margin of equatorial South America, which is characterized by a broad continental arc on top of thickened crust, comprising the Andes Cordillera. The area shows extensive and persistent Quaternary volcanism together with intense seismicity and is currently under a compressive stress regime. Orthogonal subduction of Nazca plate under SOAM plate includes the aseismic Carnegie ridge generated in the Galapagos Hot Spot, about 600 km W of the coastline. Both the continental arc and the hotspot host high heat flow anomalies, evidenced by a high density of active volcanoes. Utilization of geothermal energy is still restricted to direct use in swimming pools (5.16 MWt and 102.4 TJ/yr for annual utilization). Nevertheless, government policies aim to develop renewable energy resources including hydro, wind, solar, biomass and geothermal. Profound changes in both energy and production matrixes are underway to be completed in the next three years, mostly based on substantial increases of hydropower generation to lessen or even eliminate the use of fossil fuels. The leading agencies for geothermal energy are MICSE (Ministry for the Coordination of Strategic Resources), MEER (Ministry of Electricity and Renewable Energy), CONELEC (National Council for Electricity – Regulatory issues); CELEC EP (Public Corporation for Electricity Generation) and INER (National Institute for Energy Efficiency and Renewable Energy). Important public funding has been allocated through MEER for geothermal exploration of both high and low temperature resources. In accordance to the Constitution (2008), which dictates that no energy concessions can be granted, joint ventures are favored in government to government agreements where the State of Ecuador owns at least 51 % interest. The current energy mix is dominated by fossil fuels (51 %), hydro (47 %) and other (2%), with a total installed generation capacity of 4716.3 MWe, this results in a gross electricity production of 21838.73 GWh/yr (as of 2011), where 11 414.69 GWh are from renewable sources and 10 424.04 GWh from fossil fuels; the remainder of 1294.57 GWh corresponds to imported energy from Colombia and Peru. The 2010/2011 increase in gross energy production was 7.14%. Electricity production from renewable energy sources other than hydro increased in the last years to about 70 MWe. In this period the geothermal situation has improved substantially compared with the previous decade, although no deep drilling has taken place yet. Earlier geothermal exploration , carried out by government institutions between the late 70s to early 90s with the aid of foreign technical assistance programs, defined a combined theoretical potential (volumetric heat-in-place method) of about 500 MWe for the three most promising prospects: Tufiño-Chiles, Chalupas and Chachimbiro, located in the highlands of central-north Ecuador. Reassessment of this potential in the last years, based on surface studies including comprehensive MT surveys, multiple hypothesis conceptual models (power density method) and well siting, indicates a combined 200 MWe for the optimistic models of Chachimbiro, Chacana-Jamanco and Chacana-Cachiyacu prospects, which await deep exploratory drilling to confirm temperature. A dozen other geothermal prospects related to silicic calderas, evolved stratovolcanoes and basaltic shields should substantially increase the inferred potential. Low- to medium- temperature resources are abundant along the volcanic arc and are mainly related to NNE strike-slip faulting and local pull-apart structures; these geothermal resources are not confined to the volcanic highlands, but are also present in the fore arc plains as well as in back-arc areas, mostly related to deep cutting basement faults. The geothermal masterplan launched by MEER in 2010 for electricity generation, based on surface data only, ranked 11 prospects for prefeasibility stage studies. Three of them, operated by CELEC EP, completed geological, geochemical, and geophysical surveys integrated into multi-hypothesis conceptual models, including risk assessment, likely generating capacity, and location of deep exploration drill sites. These are: Chachimbiro, Chacana-Cachiyacu and Chacana-Jamanco, totaling 200 MWe for the most optimistic alternative, although the exploration risk is still high. Proposed deep exploration slim holes are planned to be drilled in 2014-2015 under CELEC EP, mainly to test temperature, in order to proceed into appraisal drilling if results are positive. A fourth studied prospect, Chalpatán, completed prefeasibility surface surveys and results indicate potential direct uses of the resource instead of electricity generation. A 1.85 km3 fault-controlled hot water reservoir (70-120 ºC) at 1500 meters depth is likely to exist inside of the Chalpatán caldera. A fifth geothermal prospect, Tufiño-Chiles, is a Bi-National Project located on the Ecuador-Colombia border and is subject to final prefeasibility scrutiny with complementary surface studies, mainly rock age dating, gas geochemistry and a comprehensive MT survey, to produce a geothermal model and target locations for deep exploration holes. Exploration activities are jointly funded and managed by CELEC EP (ECUADOR) and ISAGEN (Colombia), with ISAGEN being the operator. The final aim at this stage is to drill a first deep exploration hole before 2015 to test the resource model and temperature, and give way to appraisal drilling if results are positive. Three other prospects, namely Chalupas, Guapán and Baños de Cuenca, await MEER funding to complete prefeasibility stage studies, mainly geochemistry and geophysics, in order to elaborate conceptual models and site deep drill holes. A more detailed geochemical survey, funded by INER, is underway at Baños de Cuenca to evaluate the origin of fluids and possibly deep temperatures and potential uses. The last three prospects of the MEER masterplan are Chacana-Oyacachi, Chimborazo and Alcedo, which are at the reconnaissance stage and await MEER funds for prefeasibility studies. From the resource point of view, Alcedo is the most promising geothermal prospect in the country (about 150MWe), although its location in the core of Galapagos National Park renders any future exploitation impossible according to current environmental laws. These and several other |