Assessment of Geothermal Resources of South America - A New Look

Abstract

The present work provides a new look into the nature and distribution of geothermal resources of South America, on the basis of recent advances in data analysis and regional assessments. Notable in this context is the progress achieved in the use of a procedure termed as magmatic heat budget (MHB) that allow estimation of heat flux in areas of recent volcanic activity. In addition, an updated compilation of temperature gradients and heat flux have been completed. Such advances have allowed new resource assessments for 6526 sites. These span over more than 100 crustal blocks, distributed in thirteen countries of the continent. Following this, a 2ox2ogrid system with homogenized data sets were employed for calculating the in-situ heat content. Determinations of resource base based on observational data are now available for 253 out of a total of 418 cells in this grid system. Values of resource base based on estimated heat flow were calculated for the remaining 165 grid elements. The data and model results on temperatures of subsurface strata at depths less than three kilometers have been employed in classifying the resources, into three general categories: hot dry rock (HDR), hot wet rock (HWR) and low enthalpy (LE). HDR type resources, classified as those with temperatures higher than 150oC, occur in 318 localities mainly in the Andean regions. Similarly, HWR type resources, classified as those with temperatures in the range of 90 to 150oC, occur in 352 localities. Low enthalpy (LE) resources, with temperatures < 90oC, are numerous mainly in the eastern parts of the continent. The total resource base (RB) of HDR systems is estimated to be 1329x1021J and the corresponding resource base per unit area (RBUA) is 513GJ/m2. The HWR systems have a total resource base of 586x1021J, while the corresponding value for RBUA is 409GJ/m2. The low enthalpy systems, with temperatures in the range of 60 to 90oC, have a total resource base of 240GJ/m2, while those with temperatures less than 60oCis estimated to be 210GJ/m2. There are indications that HDR resources, with temperatures higher than 150oC at depths less than three kilometers, occur in 318 localities of the Andean regions. The total resource base (RB) of HDR systems is estimated to be 1329x1021J, while the corresponding weighted mean resource base per unit area (RBUA) is estimated to be 513GJ/m2. The new results have also been useful in regional scale identification of resources with notable pore fluid circulation, classified as HWR systems. Such systems with temperatures in the range of 90 to 150oC, are inferred to occur at depths less than three kilometers, in 352 localities of the Andean region. The total resource base of HWR systems is estimated to be 586x1021J, while the corresponding value for RBUA is estimated to be 409GJ/m2. Low enthalpy (LE) resources, with temperatures in the range of < 90oC, are numerous in the remaining parts of Andean regions and also in the eastern parts of the continent. The resource base per unit area of low enthalpy systems with temperatures in the range of 60 to 90oC is estimated to be 240GJ/m2, while that for systems with temperatures less than 60oCis estimated to be 210GJ/m2.