The present thesis consists in a real complex case study of halotectonic deformation in the central portion of the Santos Basin passive margin, investigating the complex interactions between deformation and sedimentation and evaluating its impacts on the petroleum systems.Seismic data set and exploration wells were input to the study, which cover an area where halokinetics affect the active petroleum systems. The thickest depocenter of the Santos basin is partially in the study area. The sedimentary infilling history is associated with the Cabo Frio Fault development, linked with a gap of tens of kilometers in the Albian sediments occurrence. Minibasins are under halotectonic compression towards deep waters. The challenges of this work consists in find methods to build and then to restore the structural model in an effective way.Fifteen interpreted horizons were used to build a surface model. Five geological cross-sections were restored and interpolated to get salt and overburden volumes. The restoration successively removes the uppermost layer and decompacts the remaining layers through sedimentary unloading. Restoration also considers the unloading isostatic compensation by flexure of an elastic weak layered lithosphere. The isostasy plays an important role in the tectono-sedimentary control. Its interaction with bathymetry, faults geometry and deposition surface profile constrains the local and regional subsidence. Biostratigraphic data and seismic pattern defined trough time the absolute paleobathymetry.The cross-section restoration has differentiated the major rift phase sequence deformation from three other drift phase sequences above the sal layer.Several 1D geo-histories were reconstructed for different points along the main direction of transport, to control the thickness variations in the 2D sections. 1D and 2D restorations clearly show that salt moves out of the study area and that there is strong coupling between the halotectonic dynamic and the change in the accommodation space.The extrapolation of the restoration results to 3D allows a better compartmentalization between the hemigrabens in the rift phase; highlights the role of structural high in the center of the investigated area and confirms the relation between structural evolution and sedimentation. Two major depocenters were amalgamated by salt deposition over the accentuated relief inherited from the larger vertical tectonic subsidence of the rift phase. The sedimentary infilling reveals the temporal relations of NE-SW and NNW-SSE oriented structures within the higher subsidence compartment in the western sector of the area. Two different ways to restore the sections allowed the uncertainty estimation of the bathymetry and isostatic relationships.The salt layer material conservation assumption, an operational tool, was consistent with the results. The salt volume balance over time showed a good correlation to lateral extension of the continental drift stage.The implications of the restoration scenario on the petroleum systems were only qualitatively interpreted and then compared to the classical backstripping approach. Three main sectors appear: the proximal shelf, the slope and the deepwater sector of the continental rise. The relatively early halotectonics of the proximal sector induces a more fast and short generation whereas, beyond the continental slope region, the petroleum systems is distally more heterogeneous, develops slower, dissipated and differentiated by the halokinesis, with longer refills fronts. The direct impact of salt restoration on the maturity evaluation is actually relatively small, because about 90% of ductile deformation occurred before 65 Ma and a significant part of the generation is ongoing after 65 Ma. On the other hand, the halotectonic restoration is fundamental regarding its impact on the petroleum systems.
| Identifer | oai:union.ndltd.org:CCSD/oai:tel.archives-ouvertes.fr:tel-00800158 |
| Date | 14 September 2012 |
| Creators | De melo Garcia, Savio Francis |
| Publisher | Université de Cergy Pontoise |
| Source Sets | CCSD theses-EN-ligne, France |
| Language | French |
| Detected Language | English |
| Type | PhD thesis |
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