Petroleum Systems of the Ogooué Delta, Offshore Gabon
B.J. Katz, W.C. Dawson, L.M. Liro, V.D. Robison, J.D. Stonebraker (Retired), 2000. "Petroleum Systems of the Ogooué Delta, Offshore Gabon", Petroleum Systems of South Atlantic Margins, Marcio Rocha Mello, Barry J. Katz
Download citation file:
An analysis of the petroleum geology of the Ogooué Delta region reveals the presence of two independent petroleum systems: the Madiela/Cap Lopez–Batanaga(.) and the Azile/Anguille–Anguille(!) systems. An independent system is defined as a suite of hydrocarbon accumulations that share a common source and reservoir couplet. The oils in the first system appear to have been generated from a pre-Cenomanian restricted (elevated salinity) marine source. These oils occur largely in Batanga Formation sandstones (Maestrichtian) and are limited mainly to the southern parts of the delta. The petroleum in the second system appears to have been generated from the Azile and Anguille Formations (Senonian) and thus developed under more normal marine conditions. This second group of oils is mainly found in Anguille reservoirs, which were deposited in submarine fans during lowstand events. This second system is geographically less restricted, being present in both the northern and southern parts of the delta.
The geographic distribution of the two systems is controlled by several factors, including the distribution of the source, the nature of the migration network, and the level of thermal maturity. Both systems share one major controlling factor: the areal limit of the two systems is in part constrained by thermal maturation. The overburden associated with the delta complex provided for appropriate levels of thermal maturation for generation to proceed. Modeling results suggest that the pre-Cenomanian marine shales and marls began generating liquid hydrocarbons during the Oligocene. The Senonian system began generating hydrocarbons during the Miocene. Both systems are still actively generating as subsidence and loading continues. The pre-Cenomanian system appears to have a more effective mechanism for vertical migration than the Azile–Anguille sourced system. This greater efficiency explains the younger age for the dominant reservoir of the pre-Cenomanian (older) system. It appears that the southward shift in the delta's depocenter may be a partial explanation for this greater efficiency.
Figures & Tables
Petroleum Systems of South Atlantic Margins
“Giant oil and gas fields have been discovered through recent exploration in the deep and ultra-deep water regions of Angola, Brazil, and Nigeria. This volume includes 1. Descriptions of the petroleum geology of more than 12 basins along the two margins 2. Discussion of various components of the petroleum systems within these basins 3. Discussion on the use of the petroleum systems concept in the South Atlantic marginal basins to classify and characterize the diversity of the systems 4. Methodologies used in the assessment of petroleum system components 5. Overviews of the different components of the region's petroleum systems. Petroleum explorationists and researchers working in the South Atlantic will welcome this addition to their libraries.
The printed version of Memoir 73 was the Winner of the 2000 Dott Award for best AAPG Special Publication.”