Abstract
Abstract Salt precipitation from the drying-out process has a profound effect on the well injectivity during the storage of carbon dioxide (CO2) in deep saline aquifers. Both gravity and reservoir heterogeneity have a significant impact on CO2-plume behavior and CO2 storage capacities. The collective effect of gravity and heterogeneity on the drying-out process by site-scale numerical simulation based on the Sleipner project had been investigated. Three site-scale permeability heterogeneous models and a fracture model had been built; simulation results showed that the gravity effect significantly increased the solid saturation at the injection well in the homogeneous model; changing the position of the injection well can change the distance that gravity can act and affect the amount of salt precipitation near the injection well. A novel conclusion is gravity and heterogeneity showed a mutual resistance relationship when considering the collective effect of gravity and heterogeneity on solid saturation. Gravity effects reduced the amount of salt deposited in the fracture model; at low CO2 injection rate, gravity force dominated CO2 flow; increased rock heterogeneity suppressed the production of salt precipitates; at high CO2 injection rate, viscous force dominated flow; and increased heterogeneity increased salt precipitation. This research is of important guiding significance for the design of site screening and injection schemes from the perspective of avoiding a large amount of salt precipitation and pressure build-up.
Highlights
It has been reported that unless there are immediate, rapid, and large-scale reductions in greenhouse gas emissions, limiting warming to close to 1.5°C or even 2°C will be beyond reach [1]
The TOUGH2-ECO2N module was used to simulate the value of solid saturation (Ss) in the injection well when CO2 was injected into deep saline aquifers
Compared with the Ss value in the homogeneous model, the heterogeneous model causes a significant increase in Ss at the injection well
Summary
It has been reported that unless there are immediate, rapid, and large-scale reductions in greenhouse gas emissions, limiting warming to close to 1.5°C or even 2°C will be beyond reach [1]. Among all the greenhouse gases, CO2 stands out as the most important GHG due to its excessive amount in the atmosphere compared to others [2]. The effect of controlling the greenhouse effect by shifting the energy mix to less carbonintensive alternative fuels and improving energy efficiency is limited [2]. Carbon Capture and Storage (CCS) is one of the effective technologies to mitigate the global warming effect [6, 7]. CCS is currently the only technology that allows the continued use of fossil fuels while reducing CO2 emissions to the atmosphere [10]
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