• Peer-Reviewed
AIChE Journal · 2007

Scaling behavior of convective mixing, with application to geological storage of CO₂

Hassan Hassanzadeh, Mehran Pooladi-Darvish, and David W. Keith

CO₂ storage in deep saline aquifers is considered a possible option for mitigation of greenhouse gas emissions from anthropogenic sources. Understanding of the underlying mechanisms, such as convective mixing, that affect the long-term fate of the injected CO₂ in deep saline aquifers, is of prime importance. We present scaling analysis of the convective mixing of CO₂ in saline aquifers based on direct numerical simulations. The convective mixing of CO₂ in aquifers is studied, and three mixing periods are identified. It is found that, for Rayleigh numbers less than 600, mixing can be approximated by a scaling relationship for the Sherwood number, which is proportional to Ra½. Furthermore, it is shown that the onset of natural convection follows tDc~Ra⁻² and the wavelengths of the initial convective instabilities are proportional to Ra. Such findings give insight into understanding the mixing mechanisms and long term fate of the injected CO₂ for large scale geological sequestration in deep saline aquifers. In addition, a criterion is developed that provides the appropriate numerical mesh resolution required for accurate modeling of convective mixing of CO₂ in deep saline aquifers.

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