Basin modelling and source rock evaluation in the Guyana Basin

The Guyana Basin contains a world-class source rock of Late Cretaceous age, but no hydrocarbon fields have yet been discovered offshore. In order to evaluate source rock maturity, we used basin modelling software to model a grid of interpreted 2D seismic sections and combined the 2D modelling results to build a basin-wide model. The burial depth, temperature, and transformation ratio of the Cretaceous source rocks were calculated from the end of the Cretaceous to the present, and mapped over the entire basin. The modelling results show that regional uplift during Late Cretaceous–middle Miocene time slowed the maturation of the Cretaceous source rock in the basin except in the south-eastern depocentre. In this depocentre, the oil window was reached during the Palaeogene, by which time few reservoir and seal rocks had been deposited. For the rest of the basin, uplift of the Waini arch and the middle Miocene regional uplift slowed maturation of the source rock. Possible reservoirs that could have received hydrocarbons from the south-eastern depocentre include Cretaceous-middle Miocene clastic rocks that pinch out against the southern flank of the Waini arch and stratigraphic traps along the shelf.