Traveltime and attenuation tomography of CO2 plume at Sleipner

Within the European project CO2ReMoVe traveltime and attenuation tomography have been applied on one of the high resolution seismic line acquired in 2006 on the Sleipner CO2 geological storage site. The aim is to gain an accurate model in depth, of both velocities and attenuation, to constrain better the quantification studies. The results obtained from the tomographyc inversion of traveltimes and spectral-centroid frequency shift, respectively, confirm the cumulation of CO2 in the uppermost layer of the reservoir, whereas within the plume, lateral variations of both velocity and quality factor values are observed. The presence of fine shale lenses, and their impact on the CO2 distribution within the plume may be the reason for these lateral variations. Through the comparison of the velocity and Q tomographic values with the theoretical curves from petrophysics studies, it will be possible to interpretate them in terms of effective variations in CO2 saturation and heterogeneities within the plume.