Long-term evolution of the Argentinean Continental margin: implications for hydrocarbon generation, migration, leakage and climate feedback

Scope
Passive continental margins are dynamic environments and are characterised by shallow shelf areas containing thick sedimentary packages derived from onshore erosion. At the same time, continental shelf regions host a large proportion of the worlds hydrocarbon accumulations and are consequently of high economic relevance. Natural hydrocarbon seepage is a process recognised to occur, in varying intensities, along passive continental margins of the Earth, where intense carbon release into the hydrosphere and atmosphere, or sequestration within the sediments, take place. Such exhalations, containing methane and carbon dioxide, contribute to atmospheric greenhouse gas contents and have a high potential to force climate change. Nevertheless quantification of these emissions and their variability through geologic time have so far not been carried out on the western South Atlantic. The Colorado, Salado and Austral Basins (Fig. 1) are ideal locations to study basin development together with the occurrence of natural gas leakage through the sediments to the seafloor. This project contributes to understand the potential effect of thermogenic gas emissions on paleo- and present-day climate. The project belongs to the DFG priority program “SAMPLE”: South Atlantic Margin Processes and Links with onshore Evolution”. Results from this project will be integrated into the Methane on the Move (MOM) project.
 

Fig. 1: Location of conjugated basins in the south segment off-shore the Argentine margin and off-shore the African margin. Inlet shows the 2D seismic grid of the Colorado Basin.

Fig. 2: The Colorado Basin in NE-SW direction across the slope area.

Goals  

• Generate a 3D Geo-Model of the Colorado, Salado, and Austral Basins evolution through time.
• Identify indications of active petroleum systems, using well data, seismic data, and geochemical data.
• Reconstruct and quantify hydrocarbon generation, migration, accumulation, and leakage history.
• Model thermogenic methane emissions to the hydro- and atmosphere through geologic time.

Methods  

• Seismo-stratigraphic interpretation, 2D seismic reflection data and integration/correlation of borehole data (Petrel TM software).
• Identification, classification and mapping of the paleo and present-day gas presence/ leakage indicators (i.e. pockmarks, mounds, gas chimneys or flat/ bright spots).
• Construction of a 3D basin-scale geomodel as input for 3D petroleum system modelling (Petromod TM software).

 

Fig. 3: Schematic diagram of fluid flow illustrating the migration pathways at the continental shelf and slope of the Colorado Basin.

Preliminary results on the Colorado Basin
We identified and mapped the major seismic sequences, and their bounding surfaces such as unconformities and regional seismic markers. Seismic-to-well log correlations, as well as the integration with biostratigraphy were carried out in order to provide a chrono-stratigraphic framework for the interpreted surfaces, as well as a detailed seismo-stratigraphic interpretation and tectono-stratigraphic analysis of the basin (Fig. 2). In addition to the seismic horizons, the major bounding fault systems and gas seepage indications were mapped on the 2D seismic sections (Fig. 3).
 

Contact  

• Markus Loegering (markus.loegering@gfz-potsdam.de)
• Zahie Anka (zahie@gfz-potsdam.de)
• Rolando di Primio (dipri@gfz-potsdam.de)

Partners  

• Petrobras Energia S.A. (PESA), Buenos Aires, Argentina
• Federal Institute of Georesources Germany (BGR)

Funding bodies  

• Deutsche Forschungsgemeinschaft (DFG) (Priority Program "SAMPLE")