●  GOALS

The goal of the Carbon Capture and Storage Division is to develop scientific understanding, tools, and technology to enable design, analysis, and risk assessment of approaches to geologic storage of CO₂, both in onshore and sub-seabed locations. The work includes experimental, computational, observational, and analytical components, as well as educational and public outreach. We develop techniques and instrumentation to monitor CO₂ storage in onshore and sub-seabed reservoirs, to understand fundamental mechanisms of CO₂ behavior in porous geological formations, and to assess safety.

●  RESEARCH HIGHLIGHTS AND ACCOMPLISHMENTS

At Kyushu University (KU), a high-pressure system for measurement of relevant properties under conditions of supercritical CO₂ storage has been built. Numerical studies of CO₂ behavior in porous heterogeneous Tako sandstone show that behavior is strongly influenced by small-scale porosity. Instrumentation continues to be developed for monitoring liquid, gaseous, and dissolved CO₂ in the ocean and in rock under high pressure. Collaboration has been initiated with the Illinois State Geological Survey, the Midwest Geological Sequestration Consortium (MSGC), and other foreign and Japanese partners in the area of rock physics, as well as fusion research to develop instrumentation to quantify relevant metal ions in brine. Planning has been completed for additional observational campaigns to study CO₂ drops and bubbles rising from natural vents in the Western Pacific, Kagoshima Bay, and near the Italian island of Panarea. The dynamics of CO₂ in saline aquifers is being studied in a Refractive Index Matched (RIM) facility by flowing surrogate fluids through a permeable bed, allowing high-resolution optical measurements in geometrically complex domains. In addition, an optically-accessible flow facility was built to probe the fundamental physics and three-dimensional interactions of a bubble plume with surrounding liquid, with application to CO₂ leakage into the ocean from sub-seabed storage. Computational work has developed an initial model for the case of axisymmetric flow driven by a density difference between the CO₂ drop and the aqueous phase, with a “clean” interface.

A significant element involves field studies of CO₂ drops and bubbles rising from natural vents in the Western Pacific and Japanese coastal waters. Experimental and computational approaches are used to understand multiphase flow relevant to risk assessment of CO₂ storage. Experiments focus on dynamics of supercritical CO₂ in porous media, fault formation due to over-pressurization, and behavior of gaseous and liquid CO₂ inadvertently released into the ocean from sub-seabed storage. Computations focus on predicting motion and dissolution of escaped liquid drops in the ocean. Collaborative efforts include use of KU field data to validate and refine computational models developed at Illinois, joint development of hydrate film models, and the use of Illinois experimental data and computational results in risk-assessment modeling at KU.

●  FUTURE DIRECTIONS

Future work will use high-pressure facilities to measure elastic wave velocities, relative permeability, and resistivity of various rock types from MGSC and other cores, and will provide estimates of CO₂ saturation. We will also study the geochemical evolution of rocks, develop a reservoir model using geophysical and geological data, and perform reservoir-scale simulations of long-term CO₂ storage. We will continue field observation of naturally-vented CO₂ bubbles and drops, develop a 3,000 m class virtual mooring system and towed vehicle system, and participate in UK-based experimental and field work directed to monitor and assess marine impacts of geological storage of CO₂. Future experimental work on CO₂ migration through porous media will introduce an immiscible fluid to simulate CO₂, allowing study of fluid-fluid interactions. We will also develop microscale pore-space models to study interactions between infiltrating and pore-saturating fluids. Two-phase plume measurements will consider dispersion of drops rising into the surrounding liquid. On the computational side, we will complete axisymmetric computations for rising CO₂ drops, absent dissolution, pressure dependencies and the presence of a hydrate film, and accounting for variation of density and viscosity with pressure/depth. We will formulate detailed models for the hydrate film, with emphasis on its mechanics and mechanisms by which CO₂ diffuses through it.