Geophysical characterization of the Devonian Nisku Formation for the Wabamun Area CO₂ sequestration project (WASP), Alberta, Canada

Geophysical characterization of the Devonian Nisku Formation in the Wabamun area, Alberta, Canada for large-scale CO₂ sequestration project has been successful in revealing two primary groups of anomalies. The first group is interpreted to be due to contrasts in lithology of the Nisku Formation. This interpretation is supported by constraints provided by well control, seismic modeling and petrophysical data. The second group is interpreted to be footprints of geological discontinuities which are induced by dissolution and karsting in a geologic formation shallower in the stratigraphy. Even though there is no evidence to indicate that the integrity of the Nisku Formation or the overlying caprock has been compromised, such geologic discontinuities should be taken into consideration if supercritical CO₂ were to be injected into the Nisku Formation. The analysis has identified favorable low-impedance high-porosity locations that could be developed for a CO₂ injection site. Those locations exhibit a good correlation with relatively high porosity-permeability zones of the Nisku Formation on maps derived from wireline data and core analysis using petrophysical analysis. Finally, fluid replacement modelling was undertaken to predict the feasibility of time-lapse seismic monitoring for detecting an injected CO₂ plume. The results suggest that changes in seismic response will most likely be subtle and that the plume will probably be at the lower threshold of seismic detectability.