Enhanced oil recovery (EOR)
Enhanced oil recovery methods (EOR) target oil that cannot be displaced using conventional water and/or gas injection.
Several fields on the Norwegian continental shelf have produced for so long that water and gas injection no longer yield sufficient oil production for economical operation, even if considerable oil resources are remaining.
The reason for this is that the residual oil cannot be recovered from the rock by injecting more water or gas. This residual oil is called immobile. Other recovery methods will be needed to re-mobilise and produce this oil.
Methods used to increase oil recovery beyond the previously mentioned IOR methods are called EOR (Enhanced Oil Recovery). Which EOR method will provide the best recovery factor depends on the specific reservoir properties in question.
The Norwegian Petroleum Directorate sees a potential for significant value creation through EOR methods for fields on the Norwegian continental shelf.
What does it mean?
Mobile residual oil
Mobile residual oil is mobile oil that has not been displaced to production wells with the aid of water or gas. In principle, this oil can be recovered with the aid of infill wells and more long-term use of water and/or gas injection.
Immobile oil is oil that cannot be displaced from the pores of the reservoir using a given displacement mechanism like water or gas injection. Enhanced methods (EOR) are needed in order to mobilise parts of this immobile oil. The immobile oil could occupy a considerable percentage of the pore volume in a reservoir – the immobile oil is also called residual oil.