Interpretation and dating of Paralic and Non-Marine Environments

Lacustrine basins provide some of the richest source rocks known and the understanding of their development within a lake-basin has to be based on an interpretation of a lake's depositional environments, variations in water chemistry, faunal & floral changes and, ultimately, geochemical analysis of its sediments. From this, the stratigraphic and areal distribution of source, reservoir rock and seal can be determined.

The maturity of source sediments can be assessed or supported through biostratigraphic methods whereby ostracod (CAI) and palynology (TAI) colour plots can be used to interpret both vertical and horizontal maturity changes. This approach is valuable when vitrinite is absent and supportive where vitrinite is present.

The production of quality source rocks within paralic to restricted marine environments is related to restricted water movement and associated anoxia following continental break-up. The continental margins of what was Gondwanaland provide prime examples of these oil-rich environments. GES' non-marine and paralic worldwide experience extends from the Permian, Cretaceous and Tertiary Basins of China and Mongolia, the Cretaceous Rifts of the South Atlantic to the Cretaceous and Tertiary paralic basins of Venezuela, Eastern Europe and the Caspian.

Sequence Stratigraphy of lake basins

Changes in faunal make-up, diversity and morphological variation identify the lake's changing depositional environments. A lake will pass through several sequences of development separated by periods of non-deposition and erosion. Deep lake basins frequently contain uninterrupted sedimentary sequences that serve to provide the complete history of accommodation space infill.

Regional Stratigraphic Reports

Regional stratigraphic reports have been produced to assist in the understanding of a region's prospectivity. For West Africa: The Kwanza Basin, Angola; The Rio Muni Basin, Equatorial Guinea; and four reports on Senegal and Guinea Bissau. For East Africa: Northern Tanzania - the Tanga Block; for the Far East: The Philippines Sulu Sea.