No abstract

CO2 has been injected into the saline aquifer Utsira Fm at the Sleipner field since 1996. In order to monitor the movement of the CO2 in the sub‐surface, the seventh seismic monitor survey was acquired in 2010, with dual sensor streamers which enabled optimal towing depths compared to previous surveys. We here report both on the time‐lapse observations and on the improved resolution compared to the conventional streamer surveys. This study shows that the CO2 is still contained in the subsurface, with no indications of leakage. The time‐lapse repeatability of the dual sensor streamer data versus conventional data is sufficient for interpreting the time‐lapse effects of the CO2 at Sleipner, and the higher resolution of the 2010 survey has enabled a refinement of the interpretation of nine CO2 saturated layers with improved thickness estimates of the layers. In particular we have estimated the thickness of the uppermost CO2 layer based on an analysis of amplitude strength together with time‐separation of top and base of this layer and found the maximum thickness to be 11 m. This refined interpretation gives a good base line for future time‐lapse surveys at the Sleipner CO2 injection site.

Since 1996, [Formula: see text] has been injected into the Utsira Formation above the Sleipner Øst field in the North Sea. During the injection period, the [Formula: see text] distribution in the reservoir has been monitored using eight repeated time-lapse seismic surveys. This seismic monitoring has shown that the [Formula: see text] is visible as thin bright reflectors within the Utsira Formation, interpreted to represent [Formula: see text] flooded layers. We show a detailed analysis of the thin [Formula: see text] layers, with respect to amplitude and time shift development. For a fixed location that becomes [Formula: see text] flooded, the amplitude first increased strongly and a small pull-up of the trough amplitude timing was observed. This response is attributed to interference between top and base of the layer, as long as layer thickness is beneath tuning thickness. This pull-up is an effect induced by wavelet distortion and not related to [Formula: see text] in overlying layers. With time the amplitude decreases and the pull-up is reduced to zero. This is attributed to the layer being thick enough for top and base to be separately resolved. Using our time-lapse observations we have estimated this wavelet distortion effect as a function of time of first flood, which has enabled us to correct for it, and estimate time shifts caused by [Formula: see text] in overlying layers. Thickness estimates derived from these time shifts complement previous amplitude derived estimates of [Formula: see text] thickness.

No abstract

CO2 storage in saline aquifers offers a realistic means of achieving globally significant reductions in greenhouse gas emissions at the scale of billions of tonnes per year. We review insights into the processes involved using well-documented industrial-scale projects, supported by a range of laboratory analyses, field studies, and flow simulations. The main topics we address are ( a) the significant physicochemical processes, ( b) the factors limiting CO2 storage capacity, and ( c) the requirements for global scale-up. Although CO2 capture and storage (CCS) technology can be considered mature and proven, it requires significant and rapid scale-up to meet the objectives of the Paris Climate Agreement. The projected growth in the number of CO2 injection wells required is significantly lower than the historic petroleum industry drill rates, indicating that decarbonization via CCS is a highly credible and affordable ambition for modern human society. Several technology developments are needed to reduce deployment costs and to stimulate widespread adoption of this technology, and these should focus on demonstration of long-term retention and safety of CO2 storage and development of smart ways of handling injection wells and pressure, cost-effective monitoring solutions, and deployment of CCS hubs with associated infrastructure. Expected final online publication date for the Annual Review of Chemical and Biomolecular Engineering, Volume 12 is June 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.