CO2 Sequestration through Mineral Carbonation
Date
2022-10-18
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Abstract
Anthropogenic greenhouse gas emissions have become a subject of increasing concern because of their association with global climate change. Carbon dioxide (CO2) is the most prevalent anthropogenic greenhouse gas, and hence reduction of CO2 concentration in the atmosphere has become an important area of research. Subsurface (geologic) storage has been proposed as a target for CO2 storage; physical, residual and solubility trapping are possible storage mechanisms. An additional promising mechanism for geologic CO2 storage is permanent fixation by means of mineral trapping. This thesis explores the use of unconventional reservoirs such as shales and siltstones as a target for mineral trapping of CO2. Although some studies of CO2 storage in shales and low-permeability (tight) reservoirs exist, most previous studies of shales related to CO2 storage have primarily focused on the evaluation of shale as a caprock to contain CO2 within more conventional reservoirs. Such studies have concentrated on caprock mechanical integrity as it pertains to leakage instead of reactivity or geochemical modification in the shale. In this research, CO2 storage in shales and siltstones is evaluated with a focus on the potential for mineral trapping. An innovative workflow and custom reactor were designed to evaluate this potential for low-permeability Montney siltstone and Duvernay shale samples, and specifically their interaction with CO2-charged brine at simulated reservoir conditions. Prior to analysis of the Montney and Duvernay samples, olivine samples were studied with the new workflow/reactor as a proof of concept. Olivine is well-known to generate carbonate at high CO2 pressures (PCO2) and high temperature in alkaline solutions. San Carlos Olivine was therefore used as a control group and tested at 150°C/150bar in a 1M NaCl + 0.64M NaHCO3 solution. Extensive conversion of the olivine to magnesite and amorphous silica was observed, confirming the viability of the new workflow and functionality of the designed reactor. Montney and Duvernay samples were then tested at 150°C/150bar in synthetic reservoir brine. Both samples underwent extensive dissolution with minor precipitation of secondary phases. Most of the precipitation occurred as an artifact of depressurization post experiment, where the Montney precipitated hematite and the Duvernay precipitated calcite. A second Montney test was conducted at 150°C/150bar in a 1M NaCl + 0.64M NaHCO3 solution to promote precipitation. In this test, precipitation of siderite occurred, but dissolution still dominated. As a result of these experiments, there appears to be limited potential for CO2 storage in the form of mineral trapping in the Montney and Duvernay reservoirs. However, the observed CO2 interactions have important implications for enhanced oil recovery in tight oil reservoirs hosted in the Montney and Duvernay formations.
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Keywords
CO2 Sequestration, Carbon Capture
Citation
Bader, A. (2022). CO2 Sequestration through mineral carbonation (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.