EOR and CO2 disposal — Economic and capacity potential in the North Sea

Abstract

To estimate the total CO2 EOR (enhanced oil recovery) potential in the UK and Norwegian sector of the North Sea a techno-economical model for CO2 injection into oil reservoirs and aquifers has been used in a scenario were many of the most feasible prospective water flooded fields are included. The fields are connected to a common CO2 pipeline system to supply the optimal amount of CO2 at any time during the CO2 flood cycle. The technoeconomical model consists of a CO2 transportation module and an EOR module that is integrated with an economic model that calculates investment costs and running costs both for injection into oil reservoirs and aquifers. By use of the techno-economical model a CO2 injection scenario that includes 18 Norwegian and 30 UK oil fields in the North Sea and unspecified aquifers has been studied. The project lifetime in the scenario is 40 years where CO2 is deposited at a constant rate of 178 million tonnes/year. The CO2 is delivered through a main pipeline infrastructure that transports CO2 from industrial sources in EU. In the early phases of the injection period most of the CO2 is delivered to oil reservoirs, but throughout the period more and more CO2 is injected into aquifers. Breakthrough CO2 from the oil reservoirs is re-circulated. Sensitivity analyses have been made for the scenario where the oil price and the price of CO2 for enhanced oil recovery have been varied. The potential for incremental oil production varies between 658 and 696 million Sm3, or between 8.5 and 9.0 % of the original hydrocarbon pore volume, for the various cases studied. The amount of CO2 stored in the oil reservoirs was 2284 mill tonnes for the 40 years injection period which is 31% of the total amount stored. The purchase price for CO2 from the sources (e.g. power industries) delivered at export terminals in Emden and Aberdeen varies between -23 and 94 USD/tonne when the oil price varies between 20 and 160 USD/bbl. For oil prices in the range 90 to 100 USD/bbl the CO2 price is close to the cost for CO2 capture (50 USD per tonne). An EOR module for miscible CO2-WAG (water alternating gas) injection has been developed. Preliminary calculations using this module indicate that the oil recovery potential for CO2-WAG is comparable to continuous CO2 injection. More water and less CO2 are produced during WAG injection, however.