Laboratory Testing and Simulation Results for High Pressure Air Injection in a Waterflooded North Sea Oil Reservoir

The Maureen field, a light oil reservoir in the North Sea which has achieved waterflood oil recovery close to 53 percent of the OOIP, is nearing the end of its producing life under waterflooding operations. This field was evaluated as to the feasibility of improved oil recovery through high pressure air injection as an inexpensive substitute for other unavailable or costly gases. Six accelerating rate calorimeter (ARC) tests and five combustion tube tests were conducted to determine the oxidation characteristics of Maureen crude oil while injecting air in the presence of reservoir rock and brine. These tests showed that Maureen oil will reliably autoignite, generate flue gas (85 % N 2 and 15 % CO 2 ) and propagate a stable combustion front. In addition with air enrichment, a first contact miscible displacement process can be maintained. High pressure air injection was then modeled as a miscible process using the history matched Maureen waterflood model; the results showed incremental oil recovery due to air injection would range from 17.8 to 26.3 MM STB (4.5 to 6.6 % OOIP) depending on the relative location of the air injection wells (flank or crestal).