Characterization and structural restoration of a Pre-salt area of the Santos Basinand the impact of paleogeography on the control of facies deposition in the reservoir

Abstract

The strong structural control exerted on the deposition of carbonates from the Barra Velha Formation (Aptian), pre-salt of the Santos Basin, during the rift and sag phases conditioned the stratigraphic and sedimentological processes that controlled the distribution and quality of these reservoirs. The understanding of how and with what intensity the structural evolution impacted the distribution of carbonate facies is crucial to carry out a predictive mapping of the reservoirs. The present study was conducted in the Iracema area, Tupi field, where 5 seismic horizons and 74 faults were mapped with the objective of characterizing and restoring the structural framework and reconstructing the paleogeography of the reservoirs during the deposition of the Barra Velha Formation. The study focuses on the interval deposited during the sag phase of the basin. A paleobathymetry surface was constructed for the restored horizons referring to the basal limits of the lower and upper sag intervals, considering the carbonate deposition depths based on recent analogous deposits and in accordance with previous studies carried out in the basin. To exemplify the application of this paleobathymetric analysis, a stratigraphic-sedimentological forward modeling was executed in the upper interval of the sag phase, allowing to reproduce scenarios of the internal architecture of the carbonate platform. The results demonstrate that the restored surface presents a better and predictive faciological characterization of the reservoir, which will condition the definition of the porosity and permeability distribution in 3D reservoir characterization works.