Print this pageFrench Guiana Margin: Geological History and Petroleum Plays
VIALLY, ROLAND, and 
ALAIN
MASCLE
The French Guiana Margin is located between 4 and 60 degrees N, between Brazil and Surinam, on the western side of the Equatorial Atlantic Ocean. In Jurassic and early Cretaceous times, the NW part of the margin (Demerara Rise) is believed to have represented the southern extremity of the Central Atlantic Rift and Ocean. Sedimentation at that time on the Demerara Rise occurred mainly in an inner shelf environment, with significant continental influxes and pulses of volcanism. As early as middle Albian times, shallow marine to open marine environments of deposition prevailed in response to the opening of the E-W trending equatorial ocean along a dextral shear zone between South America and Africa.
Exploration on the Demerara Rise was active in the 1960s and 1970s, with only two wells drilled in French waters. The first well reached the basement at depth of 2104 m below early Cretaceous sandstones and younger sediments. The second one bottomed out in basaltic lava flows of Barremien-early Aptian age. According to the available geophysical, geochemical and well data, numerical modelling has been performed to describe the maturation history of different potential source rocks of Late Jurassic to late Cretaceous ages. Accordingly, two petroleum plays can be proposed, either within the deep pre-Albian rift basin, or either within post-Albian strata related to the present continental margin.