Geopressure, Reservoir Properties and Advanced Geochemistry Analyses Along Pre-Salt in Santos and Campos Basins: From Oil Fields to Frontier Areas

Abstract

Summary A wide-range analysis of subsurface data along the Pre-Salt Province of Santos and Campos basins revealed that the whole area shares strong similarities of key characteristics, such as, reservoir-pod and pressure compartmentalization, migration pathways and thermal evolution of the petroleum system. This investigation covers formation pressure data, petroleum system modelling and reservoir characterization aiming to understand the relationship among different basin domains, structural compartments, oil cracking signature, CO2 content and GOR distributions along the study area. One of the main objectives of this work is to support a risk assessment of the remaining exploration potential of the pre-salt open acreage, helping the technical evaluation of the new concession areas for future bid-rounds with factual elements that were obtained from existing oil fields. This approach may also be useful to support the drilling planning, to expect well testing productivity, and to forecast the geopressured settings, which can be important for future field development, principally if Gas and/or CO2 are present in quantities that can impact the production. The pressure compartments were characterized from wireline information obtained in key wells along Santos and Campos Basin, in which the well-to-well analysis is exemplified in Figure 1 and the comparison among wells in different compartments is illustrated in Figure 2 . The MDT pressure points were evaluated in the wells, aiming to establish the hydrocarbon and water formation gradients, as well as to characterize the average subsurface pressure at reservoir level. The results show a clear distinction of pressure compartments along the basins, as defined in Figure 2 , although what controls the geopressured environment is not completely understood. Commonly, as reported in the literature (e.g. Bradley & Powley, 1994 ), the pressure compartments are explained by the effectivity of the seal that prevents pressure equilibration to normal hydrostatic pressure. Nevertheless, zones of high and low pressures in Santos and Campos basins are not always directly related to the salt withdrawal, suggesting that other factors as disequilibrium compaction and thermal history might be very important in the dynamics of petroleum system and preserving conditions for the accumulations.