The impact of CO2-enhanced oil recovery on oil production and lifespan of old oil pools: A Canadian example

Abstract

Analyses of oil production data from the Weyburn Midale oil pool reveal that CO2 injection substantially reduced the decline trend of annual oil outputs in an exponential way with an average decline rate of 2.5%, which is two times lower than that of the worldwide total giant oil fields (5.5% or 6.5%). Based on its production data, it is projected that without CO2 injection the pool would have ended its life by 2016 with an ultimate cumulative oil output of 448.1 million bbl (71.2 million m3) and a recovery factor of only 24.4%. However, with continuous CO2 injection, by 2055 when the pool will be celebrating its 100th birthday, it can still produce 4 million bbl (0.6 million m3) of oil annually with a cumulative output of 801.8 million bbl (127.5 million m3) of oil and a recovery factor of 43.7%, whereas an additional 9.2 TCF (259.9 billion m3) of CO2 will be poured into the pool. By 2100, after 100 yr of CO2 injection, the pool’s annual oil output could be near 1.5 million bbl (0.2 million m3) and its cumulative oil output would reach 914.0 million bbl (145.3 million m3) representing a recovery factor of 49.8%, whereas 21.3 TCF (604 billion m3) of more CO2 could be injected into and permanently stored in the pool. The CO2-enhanced oil recovery could extend the pool’s lifespan to 39 or even 84 more years.