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Book Chapter

Structural Framework of Lower Cretaceous Half Grabens in the Presalt Section of the Southeastern Continental Margin of Brazil

By
Oscar López-Gamundi
Oscar López-Gamundi
C&C Energy, Carrera 4 72-35, Bogota, Columbia (e-mail: olopezgamundi@ccenergy.com.co)
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Roberto Barragan
Roberto Barragan
Hess Exploration Malaysia, 207Jalan Tun Razak, 5400, Kuala Lumpur, Malaysia (e-mail:rbarragan@hess.com)
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Published:
January 01, 2013

Abstract

Recently acquired and processed prestack depth-migrated seismic data have helped to identify the key elements of the asymmetric Lower Cretaceous half grabens in the presalt, synrift-to-postrift transitional (sag) section of the Greater Campos Basin (Santos, Campos, and Espirito Santo basins), offshore Brazil. Evidence of such a structural configuration is provided by seismic reflection geometries, such as fanning (strongly divergent internal configuration) on fault borders, thinning (convergent internal configuration), and onlap onto flexural margins. Moreover, compaction synclines over basement footwall cutoff points have been identified. In poorly imaged areas, the termination of the divergent seismic configuration can be used to place the master fault of the half graben. Differential compaction at half-graben border fault margins caused by the contrasting nature of rift-fills and adjacent basement highs is postulated to have been a critical factor for the creation of counterregional dips necessary to form structural four-way closures at the sag level. Although the sag sequence extends beyond the underlying rift fill, commonly onlapping or draping over the basement, the key risk in these types of traps is the possibility that the overlying salt layer may rest directly on the basement. Fault-plane reflections indicate the predominance of planar fault-plane geometries. This is consistent with the absence of rollover anticlines or hanging-wall antiforms, which are a direct function of nonplanar listric faults. The final configuration of the traps may also be modified by important basin-scale factors (i.e., uplift resulting from magmatic underplating in the Santos Basin).

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Contents

AAPG Memoir

Tectonics and Sedimentation: Implications for Petroleum Systems

Dengliang Gao
Dengliang Gao
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American Association of Petroleum Geologists
Volume
100
ISBN electronic:
9781629810010
Publication date:
January 01, 2013

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