Global Opportunities for Offshore CCS on Continental Shelves

One of the successful strategies for matching anthropogenic CO₂ sources with regionally extensive geologic sinks is to develop storage sites in the offshore sediments beneath continental shelves. Conditions favoring this match include 1) concentrations of CO₂ sources near coasts and 2) accumulation of thick, geologically young sediments forming the adjacent continual shelves which contain favorable storage volumes. This strategy has been assessed and exploited for the well-known and successful ongoing as well as planned projects in the North Sea and is under consideration in Australia, China, Korea, Japan, the US, Brazil, Malaysia, and South Africa. Reconnaissance evaluation of continental shelves globally shows extensive potential in many other areas, including areas of Africa, India, South America, and Asia.

Storage resource in continental shelf settings is needed because in many regions the flat and arable land typical of onshore sedimentary basins hosts dense populations, elevating risk and decreasing public acceptance of geologic storage. These same areas are where current and developing CO₂ sources are sited.

The storage potential is related to geologic setting and evolution and therefore can be extrapolated globally. Continental shelf sediments typically form wedges, with thick, sand-rich accumulations in favorable locations near the shore. Shelf sediments are geologically young, which is favorable in that 1) original porosity is likely to be preserved (high injectivity) 2) thick aerially extensive shale beds are still ductile, (can self-heal), and 3) structural history is brief (fewer or more predictable fractures and faults than old basins).

Technical issues that are under initial exploration include:

1. Variability/ similarity of continental shelf geologic settings globally with respect to storage capacity assessment, infrastructure development and monitoring. How readily can knowledge gained in one area, for example the North Sea, be applied globally?

2. What information do stakeholders need about this resource, and when do they need it? Is this resource needed far in the future or is confidence in its availability needed soon? Do stakeholders need additional expertise with geologic storage technology to build confidence?

The results of reconnaissance evaluations of global storage potential in sediments that form continental shelves and options for next steps will be discussed.