DUSEL CO2: A deep underground laboratory for geologic carbon sequestration studies

The objective of geologic sequestration of carbon dioxide as a greenhouse gas mitigation strategy is the long-term containment of CO2 in deep underground formations. To develop a sound understanding of geologic carbon sequestration, we will build a deep underground laboratory to study the processes of storing and trapping CO2, including the risks of unintended leakage. The laboratory will be part of the new DUSEL facility at the Homestake mine in South Dakota. In this presentation, we will highlight the features and capabilities of the planned facility, to be called “DUSEL CO2”. The experimental design exploits the nearly half-kilometer vertical extent of existing “sandline” borings at Homestake. Pipes will be installed within the sandlines to serve as long flow columns. These columns will contain the CO2 and allow experimentation at the same pressure and temperature conditions as in deep subsurface reservoirs. Fill materials will mimic sedimentary layering, as well as cements in plugged wells. Instrumentation will enable detailed monitoring of flow, pressure, temperature, brine composition, geomechanics, and microbial activity. As part of the initial suite of experiments, we plan to simulate a leak in which CO2 changes from a supercritical fluid to a subcritical gas as the pressure drops during upflow over tens to hundreds of meters. We will test for possible acceleration in CO2 flow due to increasing buoyancy. Also, we will examine the interactions of CO2 with caprocks and well cements, and determine whether CO2 will enlarge flow pathways or cause self-sealing. Finally, we will investigate the effects of anaerobic, thermophilic bacteria on CO2 conversion to methane and carbonate. The findings from these unique experiments will advance carbon management technology worldwide and help reduce global greenhouse gas emissions.