Uranium release surrounding a single fracture in a uranium-rich reservoir under geologic carbon storage conditions
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ORIGINAL PAPER
Uranium release surrounding a single fracture in a uranium-rich reservoir under geologic carbon storage conditions Liwei Zhang 1,2 & Xiuxiu Miao 1,2 & Bin Wang 1,2 & Hejuan Liu 1,2 & Yan Wang 1 & Manguang Gan 1,2 & Xiaochun Li 1,2 Received: 24 June 2019 / Accepted: 6 May 2020 # Springer Nature Switzerland AG 2020
Abstract Though geologic carbon storage (GCS) is widely recognized as a promising strategy to reduce emissions of greenhouse gas (GHG), the potential for mobilization of radioactive uranium (U) from U-bearing minerals in deep subsurface due to CO2 injection remains a concern. In this study, supercritical CO2 and brine flowing through a fracture surrounded by reservoir rock containing uranium is simulated so as to study the potential of uranium release as a result of CO2 injection and the impact of various factors on total uranium release rate. Mineral compositions of the reservoir rock are from previously published literature, which mimics typical sandstone mineral compositions. The reservoir rock is assumed to have 2 × 10−4 vol% UO2 in solid phase. Simulation results show that CO2 injection induces UO2 dissolution, and both CO2 and mobilized uranium are able to migrate in both the fracture and the rock matrix surrounding the fracture. However, the released uranium concentration is quite low in a 60day simulation period. Mineral dissolution causes a very small porosity increase surrounding the fracture in the simulation period. Sensitivity analysis shows that an increase of UO2 specific surface area and UO2 content in reservoir rock causes a significant increase in released uranium concentration. In other words, total uranium release rate is positively correlated with the specific surface area of UO2 and UO2 content in reservoir rock because the increase of specific surface area and UO2 content increases the total area of UO2 in contact with HCO3− and O2, which raises total uranium release rate. In summary, uranium release in and surrounding the fracture is mainly controlled by uranium supply of the reservoir rock, and the risk of environmental contamination by CO2-induced uranium release is quite low in the scenario reported. Keywords Uranium . Fracture . CO2 storage . Porosity . Water contamination
1 Introduction Carbon capture and storage (CCS) is the separation and capture of carbon dioxide (CO2) from the emissions of industrial processes prior to release into the atmosphere and storage of captured CO2 in deep underground geologic formations [1]. CCS is considered one of a suite of technology alternatives recognized by the United Nations Intergovernmental Panel on Climate Change (IPCC) and other organizations as a technically viable approach to reduce anthropogenic CO2 emissions
* Bin Wang [email protected] 1
State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics (IRSM), Chinese Academy of Sciences, Beijing 430071, China
2
University of Chinese Academy of Sciences, Beijing 100001, China
[2–4]. The IPCC, in its fifth assessment repo
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