EXPERIMENTAL VERIFICATION OF OIL SATURATION AND LOSSES DURING SECONDARY MIGRATION

Accurate estimates of losses occurring during secondary petroleum migration are of vital importance for valid petroleum systems assessments. In this paper, we discuss the development of migration pathways and the corresponding hydrocarbon losses using data from laboratory experiments based on diphasic immiscible draining processes. These experiments permitted us to study the formation of migration pathways, the distribution of non-wetting oil along these pathways, and the re-utilization of existing pathways by later pulses of migrating oil. The configuration of a migration pathway can be characterized by a phase diagram whose coordinates are two dimensionless numbers: the capillary number and the Bond number (a measure of the buoyancy force). NMR imaging was used to measure the saturation of residual oil within the pathways. It was found that, after migration, the average residual oil saturation within a pathway was generally less than 40% at a resolution of 0.4mm. Hydrocarbon losses during migration were estimated as the product of the volumetric proportion of the migrating cluster structure, defined using this spatial resolution, multiplied by the average residual oil saturation in the pathway.