Four-Dimensional Imaging of Carbon Sequestration
Four-Dimensional Imaging of Carbon Sequestration High-resolution subsurface imaging provides models of 3D structures at depth, which include fluids, impermeable rock layers, and subsurface geologic structures. Repeated imaging detects time-dependent changes in the subsurface conditions, including those resulting from fluid extraction, fluid injection, and reservoir compaction. In carbon sequestration, where CO2 is injected into deep rock layers to isolate it from the atmosphere, it is critical to assess where the gas goes and how effectively it is contained. Seismology offers key information for identifying viable structures for sequestration, and for 4D monitoring of injection and migration. A practical example of this is shown above for the CO2 injection at Statoil’s Sleipner field in the Norwegian North Sea, which has had more than 8 Mt of CO2 injected into the reservoir. Time-varying reflection images are differenced to determine how the CO2 has distributed in plumes throughout the medium. This method ensures the integrity and maximal utilization of the sequestration reservoir. (Image from R.A. Chadwick, R. Arts, and O. Eiken, 2005. 4D seismic quantification of a growing CO2 plume at Sleipner North Sea, Pp. 1385–1399 in Petroleum Geology: North-West Europe and Global Perspectives: Proceedings of the 6th Petroleum Geology Conference, A.G. Dore and B.A. Vining, eds., Geological Society, London.)