CO2 EOR and storage in heavy oil reservoirs underlying permafrost

Injection of the captured CO2 from industrial sources in oil reservoirs can alleviate negative environmental impacts of CO2 emission into the atmosphere and at the same time provides economic rationale for CCS by improving oil recovery. Compared to light oil, heavy oils have a much larger carbon footprint and hence, from environmental point of view, are more attractive targets for CCS. Heavy oil reservoirs are usually produced by thermal recovery techniques which only exacerbates adverse environmental effects of oil production from these reservoirs. Heavy oil reservoirs can therefore be good candidates for combining CCS and EOR. Examples of such reservoirs are found on North Slope, Alaska, where huge heavy oil resources exist in shallow reservoirs at exceptionally low reservoir temperature because of permafrost. This paper presents the results of a series of coreflood studies using a heavy crude sample from a permafrost region. The experiments compare CO2 storage capacity of the rock sample at reservoir conditions under different injection strategies and determine the additional recovery as a result of CO2 injection. The results show that CO2 injection doubled the heavy oil recovery by plain waterflood however the storage capacity of the rock was not significantly affected by the injection strategy.