Petroleum System Modeling of the Orange Basin, South Africa

Seismic coverage of the study area in the Orange Basin, South Africa, and wells used to construct the petroleum system model

Basin modeling is a powerful tool for determining hydrocarbon generation and migration within a confined area. The basin modeling techniques can also be applied to study the controlling factors of thermogenic methane seepage from hydrocarbon bearing sedimentary basins.  The seismic indicators for vertical gas migration in a sediment column are gas chimneys, which are often related to pockmarks, mud volcanoes, and carbonate mounds. An active petroleum system and also gas hydrate dissociation are thought to be the source for the observed seepage features. Gas chimneys, their surface expressions, and features of buried, as well as paleo gas seepage and possibly gas hydrates have been observed on seismic data sets of the Orange Basin. Therefore the study area represents an ideal region for investigating the controls on the location, initiation and evolution of natural hydrocarbon seepage and their potential significance for hydrocarbon exploration.

This PhD-research project is financed by the Forest Oil Corporation and carried out in the framework of the MOM project (Methane on the Move).

Goals
The petroleum system model will be used to reconstruct the thermal and burial history of the Orange Basin and to simulate hydrocarbon generation, migration, sequestration, and leakage. An additional aim is to constrain thermogenic methane contribution to the hydro- and atmosphere as a function of geologic time, and thus its influence on global climate change.

 

Activation energies and transformation curve of an organic-rich sample from the Orange Basin (left), 3D view of seismic surfaces along an E-W transect through the basin center (right).

Seismic interpretation and mapping of gas seepage features on an extensive 2D seismic data set covering the entire South African part of the Orange Basin will serve as a the basis for a 3D geomodel. State of the art analysis and interpretation of 3D seismic surveys will help to understand gas and fluid migration mechanisms in relation to their geologic and structural setting.
Immature source rock samples will be analyzed for bulk-source rock parameters, petroleum type, generation potential, organo-facies variability and compositional kinetics. Up to date, compositional kinetics have not been investigated for the source rocks of the Orange Basin.
Seismic interpretation, bore hole data, compositional kinetics, as well as the results of the organic geochemical analysis will be used to construct and calibrate a 3D petroleum system model of the Orange Basin.
 

Participants
Alexander Hartwig
Zahie Anka
Rolando di Primio

Partners
Forest Oil Corporation
PASA, Petroleum Agency South Africa
Petro SA

Funding bodies
Forest Exploration International (South Africa) (PTY) Ltd.