Pioneering insights into deep groundwater movements in the Paraná Basin: Comparison with subsurface flows in the Amazon Region

We present results of a pioneering study that provide new insights into the characteristics of deep groundwater flow systems of the Parana basin. The technique employed, based on geothermal methods, is capable of providing simultaneous estimates of both vertical and horizontal components of groundwater flows. The analysis makes use of bottom-hole temperature data from oil wells. Vertical velocities of subsurface flows are found to fall in the range of 10 -10 to 10 -9 m/s while the horizontal components are generally an order of magnitude higher, falling in the range of 10 -9 to 10 -8 m/s. The results obtained have allowed identification of three different regions of up flows and five different regions of down flows, at depths ranging from 1000 to 4000 meters. The geographic distribution of such flow pattern points to complex interplays of subsurface recharge and discharge systems of groundwater in the Parana basin. This system is unlike that found in the basins in the Amazon region, where systematic lateral flows in the west – east direction is ubiquitous.