Evaluating Impacts of CO₂ Intrusion into an Unconsolidated Aquifer: II. Modeling Results

Journal Article · Tue Aug 04 04:00:00 EDT 2015 · International Journal of Greenhouse Gas Control

DOI:https://doi.org/10.1016/j.ijggc.2015.07.001· OSTI ID:1233485

Zheng, Liange ^[1]; Qafoku, Nikolla ^[2]; Lawter, Amanda R. ^[2]; Wang, Guohui ^[2]; Shao, Hongbo ^[2]; Brown, Christopher F. ^[2]

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1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Large scale deployment of CO₂ geological sequestration requires the assessment of the risks. One of the potential risks is the impact of CO₂ leakage on shallow groundwater overlying the sequestration site.The understanding of the key chemical processes and parameters are critical for building numerical models for risk assessment. Model interpretation of laboratory and field tests is an effective way to enhance such understanding. Column experiments in which CO₂ charged synthetic groundwater flowed through a column packed with material from High Plains aquifer was conducted and concentration of several constituents in the effluent water was analyzed. In this paper, reactive transport model was developed to interpret the observed concentration changes, attempting to shed light on the chemical reactions and key parameters that control the concentration changes of these constituents. The reactive transport model catches the concentration changes of pH, Ca, Mg, Ba, Sr, Cs, As and Pb fairly well. Calcite dissolution and Ca-driven cation exchange reactions are the major drivers for the concentration changes of Ca, Ba, Sr, and Cs. The pH-driven adsorption/desorption reactions lead to a concentration increase of As and Pb. The volume fraction and reactive surface area of calcite, CEC and sorption capacity are key parameters in determining the magnitude of concentration increase. Model results also show that the dissolution of calcite with Ba impurity could be an alternative explanation of the increase in Ba concentration.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1233485
• Report Number(s): PNNL-SA--106872; AA9010200
• Journal Information: International Journal of Greenhouse Gas Control, Journal Name: International Journal of Greenhouse Gas Control Vol. 44; ISSN 1750-5836
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

CO2 sequestration
High Plains aquifer
geologic sequestration
reactive transport model