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The Sleipner CO 2 storage operation has been injecting CO 2 since 1996, and the growth of the plume has been intensively monitored using time-lapse seismic techniques. Detailed history-matching of the topmost CO 2 layer has proven challenging. This paper summarizes results from a series of flow simulations examining two key parameters affecting CO 2 mobility: permeability heterogeneity and fluid temperatures within the plume. The best match to the observed distribution of CO 2 was achieved by including high permeability channels in the reservoir flow model, as observed on seismic data. Thermal models suggests that CO 2 enters the top sand layer 7 °C warmer than the ambient reservoir. The resulting reduction in the density and viscosity of CO 2 does not significantly improve the fit between seismic and simulation.

Geological storage of CO2 that has been captured at large, point source emitters represents a key potential method for reduction of anthropogenic greenhouse gas emissions. However, this technology will only be viable if it can be guaranteed that injected CO2 will remain trapped in the subsurface for thousands of years or more. A significant issue for storage security is the geomechanical response of the reservoir. Concerns have been raised that geomechanical deformation induced by CO2 injection will create or reactivate fracture networks in the sealing caprocks, providing a pathway for CO2 leakage. In this paper, we examine three large-scale sites where CO2 is injected at rates of ~1 megatonne/y or more: Sleipner, Weyburn, and In Salah. We compare and contrast the observed geomechanical behavior of each site, with particular focus on the risks to storage security posed by geomechanical deformation. At Sleipner, the large, high-permeability storage aquifer has experienced little pore pressure increase over 15 y of injection, implying little possibility of geomechanical deformation. At Weyburn, 45 y of oil production has depleted pore pressures before increases associated with CO2 injection. The long history of the field has led to complicated, sometimes nonintuitive geomechanical deformation. At In Salah, injection into the water leg of a gas reservoir has increased pore pressures, leading to uplift and substantial microseismic activity. The differences in the geomechanical responses of these sites emphasize the need for systematic geomechanical appraisal before injection in any potential storage site.