Carbon Dioxide Emission Intensity:
Steam versus Air Injection EOR


This article is intended to address a pervasive inaccuracy concerning the relative amounts of carbon dioxide generated by steam versus air injection projects. The prevailing perception is that air injection EOR has a significantly higher CO2 emission intensity than steam injection. Let us examine typical operating conditions of both types of processes.


Steam Injection


Approximately 75 standard m3 of natural gas is required to generate 1 m3 of 100% quality steam (cold water equivalent). If we assume that the natural gas is essentially methane, then burning 1 m3 of gas will produce 1 m3 of CO2.
Assuming different steam-oil ratios (SOR) allows us to calculate the amount of CO2 generated per m3 of oil produced, the CO2 intensity. 

The table shows CO2 intensities for SOR’s from 2 to 6. The best SAGD projects have SOR’s from 2.0-2.5 and average projects are in the 4.0-6.0 range. For typical projects we can therefore expect a CO2 intensity of around 400 ST m3 / m3 oil. 


Air Injection


If we assume that during underground combustion there is equimolar replacement of the oxygen in the injected air to form CO2, then 1 m3 of oxygen will burn hydrocarbons to produce 1 m3 of CO2

The most efficient air injection projects make use of gravity and have lower air-oil ratios (AOR), in the range 800 to 1,000 standard m3 per m3 of oil. On average, however, the AOR’s are around 2,000. For typical projects we can therefore expect a CO2 intensity of around 400 ST m3 / m3 oil. 


Conclusion


While individual projects may have superior or inferior performance, on average, air and steam injection projects will have essentially the same CO2 emission intensity.


October 2010 


Previous PageNext Page