Reconcavo Basin, Brazil

The Reconcavo Basin of Brazil is a structurally complex failed rift surrounded and floored by Precambrian basement rocks. During the Early Cretaceous lithospheric stretching associated to the break-up of Gondwana led to the formation a rift basin with extensive lacustrine deposition. The opening of the Atlantic Ocean to the east of the Reconcavo basin terminated its development at this early stage. The main source rock sequence is the lacustrine freshwater shale of the lowermost Cretaceous Gomo Member of the Candeias Formation (Rudkiewicz et al., 2000). Reservoir rocks are found within the Late Jurassic pre-rift Aliana and Sergi Formations (eolian and fluvial sandstones) as well as in the syn-rift Candeiras and Marfim Formations (turbiditic sands). While the pre-rift reservoirs are predominantly structural traps formed during the rifting, the syn-rift reservoirs consist mainly of stratigraphic traps (Mello et al., 1994). Geochemical and basin modelling of the Reconcavo Basin (Mello et al., 1994; Rudkiewicz et al., 2000) indicates that petroleum generation and migration started during the Aptian and continue up to the present in certain parts of the system.

Basin modelling of the Reconcavo Basin was performed following the results of the 2D model of Penteado (1999), discussed in Rudkiewicz et al. (2000). Model geometry and erosion history were identical, only the heat flow had to be adapted due to the use of a different basin modelling software package (Petromod V.8, IES, Germany). The fit to calibration data was, however, as good as reported in Penteado (1999) and Rudkiewicz et al. (2000). The fluid produced from the field marked in Figure 20 consists of an undersaturated black oil, with a GOR of 110 Sm3/Sm3 and a Psat of 18 MPa. We implemented the compositional kinetic model developed for the organic facies 5a (BH005) as representative of the lacustrine source rock sequence of the Gomo Member. Model predictions using the calibrated basin model indicate a field GOR of 145 Sm3/Sm3 and a saturation pressure of 16.5 MPa.