Basin and petroleum systems modelling is a powerful tool in petroleum exploration, but uncertainties remain in terms of the evaluation of a petroleum accumulation's size and quality, even when the petroleum system is well known and the latest modelling technology is applied. In order to interpret the results of a modelling exercise, it is necessary to understand the advantages and disadvantages of the various possible approaches used to assess petroleum migration and accumulation. This paper attempts to compare the influence of different migration modelling techniques – the flowpath, Darcy “hybrid” and invasion percolation approaches – on basin-wide mass balance calculations for a temperature- and pressure-calibrated, numerical four-dimensional basin model. The study was performed using PetroMod® software.
The study area is the well-known Jeanne d'Arc Basin located offshore Newfoundland, eastern Canada. Model predictions were verified against pre-existing data including the quantity and quality of discovered hydrocarbons in the basin. Modelling results showed that the Darcy method produced substantially different results compared to the other migration techniques and this was due to the high accumulation efficiency. The flowpath method, and a combination of flowpath and Darcy methods (referred to as the “hybrid” method) yielded similar results; furthermore, the hybrid method predicted the petroleum composition quite accurately. The invasion percolation method gave similar results to the hybrid approach, but little or no variation in API and GOR across the basin was predicted.
The adsorption model initially applied did not adequately reproduce the natural behaviour of source rocks with respect to petroleum expulsion efficiency. Therefore a revised model was implemented in which the adsorption capacity was reduced with increasing maturity. This revised adsorption model led to more realistic volumes of hydrocarbons being retained within the source rock. The application of this approach had only a minor impact on the volume and quality of the petroleum present in the reservoir units.