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SCCS Winter Seminar - Dr. Qingyun Li

Date(s):March 01, 2017
Time:3:30 PM
Location: Green Earth Sciences Building Room 365

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Contact: Anshul Agarwal
Description:

Nanoscale Mechanisms and Macroscale Observations in CO2-deteriorated Wellbore Cement

 Analyzing reactive transport in porous media at multiscale
has been a challenge for geochemists. It has been questioned whether nanoscale
geochemistry is important for field applications such as geologic CO
2
sequestration. This presentation will answer this question with solid data from
experiments and modeling. Wellbore cement was used as a model porous medium for
investigation. It is an important medium to study also because cement
deterioration could lead to CO
2 leakage and impair sequestration
efficiency.  Experimental results show
that after CO
2 attack on cement, mechanical deterioration was as
significant as 80%. Several reaction zones observed at microscale in the cement
matrix were critical for this deterioration. To understand the cement
deterioration process at nanoscale, we built a continuum reactive transport
model using CrunchFlow. The model can reproduce experimental trend only if the
modeling code incorporates nanoscale mechanisms. These mechanisms include pore-size-dependent
precipitation, mineral nucleation, and impurity incorporation during mineral
precipitation. Additional experiments proved validity of the nanoscale
mechanisms incorporated in our numerical simulation. These experiments also revealed
surprising effects of ion adsorption on macroscale mitigation of cement
deterioration. Implications for industry will also be discussed. This
presentation is expected to bridge understanding across scales, improve
communication between experimental and modeling communities, and provide
industrial implications obtained at basic science level.