Carbon geological storage --- Underlying phenomena and implications

This thesis explores fundamental concepts related to carbon geological storage, including the possibility of CO2-CH4 replacement in hydrate-bearing sediments. CO2 and CH4 have pressure-temperature dependent physical properties and interaction with water. These complex interactions in the pore space of natural formations call for specific experimental and analytical research methods to study ensuing chemo-hydro-mechanical couplings in geological systems. This research is based on experimental methods, and is complemented with numerical and analytical techniques to gain a fundamental understanding of the following phenomena:;Interfacial properties of water, mineral, CO2 and CH4 systems. Interfacial tension and contact angle are needed to define multiphase interactions and fluid flow in enhanced gas recovery operations and in CO2 injection and storage in geological formations. Two sections document interfacial tension and contact angle measurement for CO2-watermineral and CH4-water-mineral systems and their implications.;CO2 sealing capacity of clayey cap rocks. The interaction between clay particles and CO2, and the response of sediment layers to the presence of CO2 affect the sealing efficiency of clayey cap rocks as CO2 trapping structures at injection sites. This study includes a specially designed device to test over-consolidated clay plugs to determine CO2 breakthrough and CO2 permeability in highly compacted fine-grained sediments.;Coupled processes and anticipation of potential implications for CH4-CO2 replacement in hydrate-bearing sediments . The replacement of CH4 by CO2 in methane hydrate requires specific conditions and affects the behavior of the host formation. Results include physical monitoring data gathered for pure CH 4 hydrate and for CH4 hydrate-bearing sediments during and after CO2 injection. These studies investigate the time and space scale of CH4-CO2 hydrate replacement and the hydro-mechanical implications.;Experimental and analytical results highlight the prevailing chemical, hydrological, and mechanical processes, their couplings, and emergent phenomena that are critical in defining the response of geological formations to long term CO2 sequestration.