COLOMBIA, COUNTRY UPDATE Claudia Alfaro1, Nelson Bernal 2,Gilma Ramírez3, Ricardo Escovar4 1,2,3,4 INGEOMINAS, (The Colombian Geological Survey). Dg. 53 No. 34-53. Santa Fe de Bogotá, Colombia Key words: Colombian geothermal resources, Colombian active volcanoes. Surface manifestations (hot springs, geothermal exploration, geothermal map of Colombia, hydrothermal eruption craters, steam vents, etc.) Azufral volcano geothermal system, Geothermal well suggest that there is a high probably of the occurrence Nereidas 1, Colombian hot springs. of hydrothermal systems related to these potential heat sources. Until now, geothermal resources have been applied in Colombia only for direct use of hot spring ABSTRACT water for swimming and bathing in about 38 spas from 27 localities. A raw estimate of the capacity and energy After more than 30 years of trying to develop the geothermal use is presented in Table 1. potential of Colombia, a major effort is now being made to explore and assess the geothermal resources of the entire [Table 1] country. Since the second quarter of the Nineteen Century, hot Until now, the availability of conventional energy sources in springs occurring in Colombia have attracted the Colombia prevented geothermal exploration from reaching a interest of scientists. In 1829, Boussingault (in Forero, higher level. However, the extreme energy crisis of 1992 – 1993 alerted the authorities and the community to the 1958), described the hot springs from Paipa necessity for exploring alternative energy sources. (Cundinamarca Province) at the Academy of Sciences in Paris. A century later, Navia and Barriga (1929) In 1997, GESA (i.e. Geoenergía Andina S.A.) drilled studied the chemistry of those hot spring waters (23- Colombia’s first geothermal well at the Las Nereidas 74°C). They also studied gases, muds, flaky deposits, geothermal prospect. This well allowed the scientific staff to the geology of the area, and the therapeutic utilisation determine some of the characteristics of the geothermal of the waters. Their more remarkable findings were an system, where permeability seems to be related to faults. Also unusually high salinity of the waters (around 40 g/l) due in 1997, Ingeominas (i.e. The Colombian Geological Survey) mainly to sodium sulphate, and the occurrence of salt undertook geothermal exploration of Azufral volcano, starting with geology, volcanology and geochemistry. These strata (banks). The salt strata, which are presumably preliminary studies indicate the possibility of a reservoir at related to the salinity of the waters, consist of sodium 200-250°C (according to empirical geothermometer sulphate, chloride, and bicarbonate that originate from calculations) in a mature strato-volcano. This project is Cretaceous sea deposits. The volcanic activity of the intended to produce electrical energy for the Nariño province. Pliocene and its sulphur contribution (H2S) are responsible for the sulphate formation. For these waters, In 1999, an evaluation of the existing information collected an important volcanic component was postulated based and processed by Ingeominas on chemical characteristics of on the contents of boron, phosphorous, arsenic, bromide thermal springs and temperature data in oil wells showed the and iodine. The meteoric component was presumably advantage of constructing a Geothermal Map of Colombia. This map will help determine Colombia’s potential for direct due to infiltration from a lake named Laguna de Tota, and indirect utilization of geothermal resources. It will also located 25 km away and 300 m above the level of the help the government and private investors locate suitable springs from Paipa. targets for further exploration. With these projects, Colombia hopes to start exploiting its geothermal resources and decrease Systematic geothermal exploration began about thirty years the serious environmental impact caused by the production of ago. The chronology of the main exploration studies can be fossil combustibles and other conventional sources of energy, summarised as follows. See location of the study areas in such as gas and coal-fired plants. Fig.1. The objectives of this paper are (1) present an overview of the 1.1. 1968. Geothermal regional reconnaissance study at geothermal resources and exploration studies in Colombia, the Ruiz Volcanic Complex. This study represents the and (2) summarize the studies being developed in Colombia starting point of geothermal research in Colombia. It was that focus on a new stage of exploration. commended by the Central Hidroelectrica de Caldas to the Ente Nazionale per L’Energia Elettrica in order to assess the 1. INTRODUCTION geological situation of the region, to determine if there are favourable conditions for deep fluids that can be used for As determined from the first exploration stages, the electrical energy production, to determine preferential areas, Colombian range of volcanic mountains contains a and to formulate a plan for the exploration. remarkable regional thermal anomaly. Evidence of this anomaly are the extended periods of magmatic activity From the geology, an extensive thermal anomaly on a regional scale was indicated along with local anomalies on and the existence of numerous active and recently 45 Alfaro et al. SW-NE and NW-SE orthogonals; these were recommended as The intense volcanic activity supports a regeional thermal priorities areas. A few hot springs were sampled and analysed. anomaly. A restricted area at the SW of Nevado del Ruiz was A meteoric origin was established for the thermal waters, identified as the most promising area from a geothermal point which have isotopic compositions that change as a function of of view due to the concentration of active or recent volcanoes elevation. Oxygen-18 enrichment was determined for hot (Cerro España, Santa Isabel, El Cisne and El Ruiz, although springs in the Botero Londoño Zone (West flank at Nevado they do not show a complete magmatic evolution), the del Ruiz), suggesting deeper circulation. Two separate existence of fumaroles discharging gases at 83-85°C (Laguna circulation systems were proposed, matching the two types of del Otún and Las Nereidas) and high temperature neutral waters, sulphate above 3000-3500 m and chloride and chloride hot springs (93°C) with high geochemical bicarbonate at lower elevations. temperatures (>200°C). The geological formations consist of the pre-eruptive basement and tertiary and quaternary A plan for further studies including geology, geochemistry volcanics with low primary permeability. However, the and geophysics was recommended substrate of the current volcanoes consists of a lava sequence with intermediate to high secondary permeability according to 1.2. 1982. Reconnaissance study of the Geothermal vertical fractures. An aquifer could be formed in the contact Resources of Colombia. This study carried out by OLADE et between the lavas and the basement rocks. The drilling targets al., excluded the Nevado del Ruiz Volcano Complex. Based were recently fractured areas presumably related to the rise of mainly on geological and geochemical studies, nine (9) areas hot fluids. This requirement was found in the zones known as were identified as potential geothermal systems. They were San Vicente-Botero Londoño, Laguna del Otún and Las preliminarily classified as high, middle and low priority Nereidas. The volcanic cover exhibits the greatest thickness at geothermal exploration targets. The high priority systems, Laguna del Otún and Nereidas, meaning that the probability Chiles-Cerro Negro and Azufral volcanoes, are recent of finding deep aquifers increases in these areas where high stratovolcanoes with a complete magmatic evolution (SiO2 temperature steam leaks occur. 59-69% and 60-71.5%, respectively); their substrate consists of thick Tertiary pyroclastic deposits and both exhibit thermal To the South of the study area, Machín volcano stands out as manifestations such as phreatic eruption craters and hot a priority due to its recent age, the existence of a caldera, the springs with high boron that could be related to the rise of relatively advanced degree of magmatic evolution (dacites) geothermal brines. Additionally, the characterisation of and the geochemistry of surface manifestations including 87- xenolytes from Azufral volcano showed hydrothermal 94°C fumaroles (steam vents) with high H2/CH4. This zonation typical of high temperature systems. The Paipa and indicates high temperature gases and hot springs with Iza area was classified as high-middle priority. Although this evidence of geothermal steam leaks (high CO2 discharge). Its system occurs in sedimentary rocks (Cretaceous formation) substrate consists of the same type of rocks as the rest of the where the permeability should not represent a problem, the volcanic complex, and has a large number of fractures and heat source presumably corresponds to ancient volcanism micro-fractures that could increase the permeability, as the (lava of 2.5 million years) with rhyolite deposits (71.5% thermal manifestations on basement rocks suggest. SiO2). Many hot springs occur in these towns with the highest temperature close to 60°C. The Cumbal and Galeras At the conclusion of this study, the areas of Nereidas, Laguna volcanoes were classified as middle priorities basically for del Otún and Machín volcano were chosen as drillling targets. their hydrological conditions. These are active stratovolcanoes with a moderate to limited magmatic evolution (60-64% SiO2 1.4. 1987. Geothermal prefeasibility