Abstract

This study reports injectivity data for the different flow zones present during a Water-Alternating-Gas (WAG) flood. The experiments were carried out on four rock types sampled from the Grayburg dolomite formation in West Texas. We used liquid CO-water, toluene-liquid CO-water and crude oil-liquid CO-water systems to isolate mechanisms and to address wettability concerns.

We found that the injectivity of the chase water zone was comparable to the initial waterflood injectivity, and increased as the trapped CO dissolved. The injectivity of the CO-rich zone was significantly higher than the initial waterflood injectivity. Ambient condition toluene tests and reservoir condition crude tests gave similar results for the water and CO zones. However the crude oil, even prior to any CO injection, exhibited a strong tendency to plug the core samples. We were unable to restore permeability in the plugged up core samples by continuous flushing of different solvents.

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