POTENCIAL GEOTÉRMICO DA BACIA SEDIMENTAR DE TAUBATÉ BASEADO EM DADOS DE PERFILAGEM GEOFÍSICA EM POÇOS – REGIÃO LESTE DO ESTADO DE SÃO PAULO

Abstract

Geothermal fields were studied in the Taubaté sedimentary basin, situated in the eastern portion of the state of São Paulo. Geophysical log data of thirty-seven supply wells were analyzed allowing determination of crys- talline basement depths, descriptions of lithological profiles (percentage of sandstones, siltstones and shales), and temperature values. Results indicated deeper sediment filled areas in Pindamonhangaba and Taubaté regions. The most dominant types of lithology are: sandstones occurring in areas between Jacarei and São José dos Campos and between Lorena and Cachoeira Paulista; siltstone in Taubaté, Pindamonhangaba and Lorena, and shale occurring in areas between Pindamonhangaba and Guaratinguetá. Analysis of geophysical profiles indicated low values of ther- mal gradients in areas of sandstones, relative to those in shale areas, attributed to differences in thermal conductivi- ties of these lithologies. The region extending from Taubaté to Guaratinguetá is found to have geothermal gradients of 70º C/km, considered anomalous. The average geothermal gradient of Taubaté basin is estimated to be 57º C/ km, which is also considered high for stable tectono-thermal regions of Brazil. It is possible that the relatively high val- ues of geothermal gradient in this basin are due to the residual heat of intrusive alkaline rocks.