Results of regional-scale geothermal studies are presented, providing new insights into the characteristics of fluid flows within deep sedimentary layers of the Campos basin. The study is based on bottom-hole temperature data sets for 76 oil wells, the depths of which vary from 2000 to 4000 m. The techniques employed in data analysis have allowed identification of upflow of fluids in both shallow and deep sedimentary layers. Specifically, temperature profiles of 15 wells are found to have non-linear features indicative of upflow. The geographic distributions of these wells indicate presence of two distinct groups of flow systems that operate in shallow and deep depositional environments. According to the results obtained vertical velocities of fluid flows are found to fall in the range 10 -10 to 10 -9 m/s, while the horizontal velocities are considerably higher, of the order 10 -8 m/s.