A study of CO2 storage capacity estimation in sedimentary rocks

The steady increase of human activities over the years has led to high atmospheric concentrations of greenhouse gases such as CO2 resulting in a steady rise of temperature levels, particularly over the last two decades. Therefore, the appropriate long-term storage of CO2 offers an attractive solution to reduce CO2 concentration in the atmosphere, especially in terms of storage of CO2 in abandoned coal seams with the potential of CH4 recovery (ECBM). However, previous studies on CO2 storage estimation methodologies in various sedimentary rocks are not adequate. Therefore, this study is focused on understanding and improving CO2 storage capacity estimation in sedimentary rocks. This thesis is a comprehensive summary of many aspects of my research, outlines the technical aspects of the research. CO2 storage estimation in sedimentary rocks has been studied comprehensively in numerical, empirical and experimental studies using a novel experimental set-up for coal and saline aquifers. This research aimed to understand and evaluate CO2 storage capacity in underground sedimentary rocks. Consequently, it is hoped that this research make a major contribution to climate warming studies as it focuses on CO2 storage estimation methodologies in coal and saline aquifers empirically, numerically and experimentally. Advanced experimental equipment has been developed with advanced features to observe pressure development along the sample. This equipment has the ability to regulate pressure and temperature. This apparatus was used to conduct permeability tests and storage estimations for Victorian brown coal specimens to investigate the effects of sub-critical and super-critical CO2 injections. The reconstituted coal samples were developed in the apparatus by compacting crushed coal using axial pressure loads. CO2 was then injected into the coal core while monitoring the injected CO2 under controlled pressure and temperature. Due to CO2 injection, coal swells as CO2 is adsorbed to the coal matrix. However, at increased pressures coal swelling increases,leading to increased storage capacity. Importantly, N2 has the potential to reverse CO2-induced swelling, recovering the lost permeability due to CO2 injection. Uniaxial compressive strength (UCS) testing was conducted on a reconstituted coal sample to observe compression load monitoring with an ARAMIS camera system. In this way, a compression load of 1.12 MPa was observed, which is consistent with the compression load observed for previous UCS compaction of Victorian brown coal specimens. Numerical modelling was carried out using field-scale data as well as laboratory data using the COMET3 numerical simulator. The calibrated models showed good agreement with the field-scale model and the laboratory data. Then a sensitivity study was conducted to investigate the effects with respect to different coal parameters. Adsorption models were reviewed to investigate the accuracy of previous adsorption models, and adsorption models have been developed based on coal properties for bituminous coal types.