Pore Pressure Predictions in Ultra-Deepwaters of Sergipe Sub-Basin, NE Brazil

Abstract

Prediction of pore pressures in large parts of a basin is very important to assure advancement of exploration, within safety limits, and to avoid risks related to anomalous pressures found in deep water frontiers. In Brazil, the Sergipe Sub-basin is located in the northeast of the country, corresponds to an Atlantic-type rifted basin with deep grabens controlled by large distensive rotational faults. The sub-basin represents one of pioneer and important areas of oil and gas production in this country with a renewed interest in the last decade for deep and ultra-deepwater opportunities. Despite that, the pore pressure in that area still little known. Thus, in these research we estimate the pore pressures throughout the stratigraphic units drilled by the P978-11 well, hoping in that way to contribute for future models of pore pressure in the basins of NE Brazil. For that, we applied on the sonic log of the P978-11 well the traditional Gardner and Eaton equations, but with own parameters values for the area, and then smoothed and calibrated the final results by loess regression. Four pore pressures zones were found ranging from 28 MPa to 89.4, suggesting an overpressure behavior in the Zonas 3 and 4.