Use of CO2 to increase oil recovery

The Norwegian Petroleum Directorate has estimated that there is a significant technical potential for improved oil recovery through the use of CO2 in oil fields on the Norwegian continental shelf.

As oil fields enter into a mature phase, the pressure in the reservoir diminishes and additional pressure support is needed to maintain production levels. Water or natural gas is used as pressure support to maintain production levels on quite a few oil fields on the Norwegian continental shelf. Injection of CO2 can be an alternative or supplement to use of water or natural gas as pressure support. In some cases, CO2 is miscible with the reservoir oil, and can thus contribute to enhancing production beyond what can be achieved through water or gas injection.

Significant challenges are associated with using CO2 to increase oil production from
fields on the Norwegian continental shelf. Particularly costly are modifications of existing installations and equipment for injection and treatment of reproduced CO2. Several of the relevant candidates for CO2 injection contain large volumes of gas, and reproduced CO2 must be separated from the gas in accordance with sales gas specifications. These processes require considerable space, and in many cases a new installation will have to be built in order to make room for the equipment. An oil field needs CO2 deliveries for a much shorter period of time than the anticipated lifetime of a gas fired power plant. In addition, the need for added CO2 will diminish as more and more CO2 is produced with the process stream. There is not necessarily concurrence between access to CO2 from a gas fired power plant and the CO2 needed by an oil field. Therefore an infrastructure for CO2 transport must be developed that makes it possible to store CO2 as the need for CO2 to improve oil recovery on a field is reduced and oil production is shut down. Larger volumes of CO2 are needed when CO2 is to be used to increase oil recovery. CO2 from a single point source will not provide sufficient volumes for optimal injection into an oil field. It may therefore be necessary to obtain CO2 from other sources in Norway or from abroad.

(Revised 15 August 2008)