Datapages, Inc.Print this page

Supra-Regional Comparison of Major Controlling Factors on Hydrocarbon Generation in South Atlantic Conjugate Margins

Marcano, Gabriela *1; Anka, Zahie 1; Di Primio, Rolando 1; Hartwig1, Alexander 1
(1) Section 4.3 Organic Geochemistry, GFZ German Research Centre for Geosciences, Potsdam, Germany.

This work presents a regional comparative approach carried out in two pairs of conjugate passive margins in eastern and western South Atlantic: (1) Brazil (Campos Basin)-Angola (Lower Congo Basin), northern non-volcanic affected by salt-tectonics and (2) Argentina (Colorado Basin)-South Africa (Orange Basin), southern volcanic, not affected by salt-tectonics. After a comprehensive compilation seismostratigraphy, tectonics, subsidence and heat flow data, we evaluate the major internal and external factors controlling the hydrocarbon generation and leakage in these basins. Our analysis is not only focused in an E-W comparison, but also a N-S comparison along the South Atlantic.

In each case petroleum system modelling, from shelf to deep basin, provided timing of petroleum generation from syn-rift and post-rift source rocks (SRs), which compared with sedimentary rates, change of depositional-mode (progradation to aggradation), occurrence of mass transport deposits (MTD), sea-level fluctuations, and major geologic events (uplift/erosion), reveals these preliminary observations:

(1) Syn-rift SRs are currently mature to over-mature, and reach complete kerogen conversion (TR=100%) since Cretaceous times. The southern margin reaches the oil window during syn-rift subsidence, whilst in the northern margins maturity seems controlled by salt tectonics during early post-rift subsidence.

(2) Post-rift SRs show nowadays high-variable extents of kerogen conversion (TR from 20 to 100%). Hydrocarbon generation (Ro>0.5) occur due to high sedimentation rates during Late K-Paleocene (southern pair) and Oligo-Miocene (Angola margin) times. Interesting is the fact that deposition of slope MTDs, linked to margin instability, predates the timing of maximum TR in the Colorado Basin, whilst it follows timing of maximum TR in the Orange and Lower Congo Basins.


AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California