Abstract: The Petroleum Systems of the Ogooue Delta, Offshore Gabon
B. J. Katz, William C. Dawson, L. M. Liro, V. D. Robison, J. D. Stonebraker
An analysis of the petroleum geology of the Ogooue Delta region reveals the presence of two independent petroleum systems. The first system appears to have been generated from a pre-Cenomanian restricted marine source. These oils are largely reservoired in Batanga Formation sandstones (Maastrichtian) and are deposited principally along the southern margin of the delta. The second system appears to have been generated from the Azile and Anguille Formations (Senonian). These Upper Cretaceous oils are reservoired principally within Anguille reservoirs. These accumulations appear geographically less restricted, but appear most concentrated within the northern portion of the delta.
The geographic distribution of the two systems appears to be controlled by several factors including the distribution of the oil-prone source, the nature of migration network, and the level of thermal maturity. The pre-Cenomanian system appears to have a more effective mechanism for vertical migration than the Azile-Anguille sourced system. It is unclear as to why differences in the migration network should exist within a single delta complex. Although the two systems have different source rocks they both share one major controlling factor. In both cases the areal limit of the petroleum system is constrained by thermal maturation. The overburden associated with the delta complex provided for the appropriate levels of thermal maturation. Modeling results suggest that the pre-Cenomanian system began generating liquid hydrocarbons during the Oligocene. The Senonian system began generating hydrocarbons during the Miocene. Both systems are still actively generating hydrocarbons.
AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela