Aquistore Completes First Crosswell Seismic Survey Since CO2 Injection Began

One of the objectives of the Aquistore project – which has seen over 393 kilotonnes of CO₂ injected 3.2 km underground into a deep saline formation – has been to track the growth of the CO₂ plume over time. To date, this has been accomplished by surface-based 4D seismic imaging (4 time-lapse images have been produced since injection began) and PND logging in the observation well.



4D seismic maps the gross-scale outline of the growing CO₂ plume in the sandstone and brine of the Deadwood formation, whereas PND logging in the observation well provides a detailed vertical profile of CO₂ saturation at the wellbore.

In mid-December, PTRC completed a crosswell survey at the Aquistore site, which offers another way of imaging the CO₂ in the reservoir, but with much higher resolution.  There are two wells at Aquistore – an injector and a monitoring well, located about 150 metres away from each other – and a baseline crosswell survey was done prior to the start of injection in March of 2013.

“Crosswell seismic provides the only means of obtaining detailed tomographic images of the CO₂ plume in the 150 m between the injection and observation wells,” notes Dr. Don White from the Geological Survey of Canada and a member of the Aquistore Science and Engineering Research Committee. “A crosswell survey will potentially delineate variations in CO₂ saturation within this zone on the scale of metres.”



A detailed understanding of how CO₂ displaces brine in situ is essential for estimating storage efficiency factors, which ultimately dictate actual storage capacity in the Deadwood formation. Interpreting the data from the survey has just begun, with findings expected this summer.