Effect of Impurities on Subsurface CO 2 Storage Processes

This chapter evaluates the potential effect of highly reactive impurities (SO x , NO x ) on two important aspects of large-scale geological storage of CO 2 —well injectivity and enhanced oil recovery processes. The primary influence on well injectivity is expected to be geochemical alteration of the near-well formation. The simulations of a “worst-case” scenario indicate that the net change in mineral volume is likely to be small, even though extensive changes in the type of minerals may occur. Thus, the effect on injectivity is likely to be insignificant. The presence of impurities in their likely concentrations of less than 1 mole% may speed up the reactions, but otherwise should have little incremental effect on the injectivity. The effectiveness of enhanced recovery processes using CO 2 depends on factors such as minimum miscibility pressure (MMP), mobility ratio, and gravity number. Correlations for these factors developed over several decades of field experience in CO 2 flooding indicate that impurities at the levels typical of flue gases are unlikely to affect recovery adversely.