AbstractThe extraction of oil from oil reservoirs beneath the North Sea has stimulated an immense popular interest in oil exploration and production. The mass media cover many of the sensational aspects of the industry but the mechanisms of the production of oil from the reservoir are not often mentioned. This is partly because the reservoir is a huge heterogeneous volume hidden underground, but also because some background in science is required. The mechanisms of oil recovery depend to a great extent on what happens at the interface between the displaced and displacing fluids at the pore scale (μm) and the reservoir scale (km). Oil is left unrecovered in areas of the reservoir where the displacing fluid has not passed (by‐passed zones–sweep efficiency) and as droplets trapped in the pores in areas where displacement has occurred (microscopic residual oil–pore displacement efficiency). The physics at the interfaces, including the interplay between capillary, (interfacial tension, wettability), viscous and gravity forces is fundamental to an understanding of the retention of this residual oil (a common reservoir average estimate is over 60%) trapped by the capillary forces or by‐passed by the displacing gas or liquid due to inhomogeneity of the reservoir. The alteration of the balance of these forces is the key to enhancing the oil recovery, either by sweeping new areas of the reservoir or recovering some of the microscopically trapped oil.This article is written to provide some of the background to oil production in the context of enhanced oil recovery (EOR). It firstly covers oil recovery that is normally practised, then describes the EOR techniques currently under active development and finally discusses some of the problems that research must overcome before EOR can be successfully implemented with confidence.