Characterisation of Major Overburden Leakage Pathways above Sub-sea floor CO2 Storage Reservoirs in the North Sea (CHIMNEY)

Academics from the University of Southampton, the University of Edinburgh, and the National Oceanography Centre (NOC) are working together to understand more about the hazards involved in the storage of CO₂ in depleted oil and gas reservoirs and saline aquifers in the North Sea.

Carbon Capture and Storage (CCS) is recognised as an important way of reducing the amount of CO₂ added to the atmosphere, and oil and gas reservoirs and saline aquifers are the preferred storage location of most European nations. However, the safety of such storage is dependent on fully exploring the risks of any leakage.

The four-year CHIMNEY project is developing better techniques to locate these sub-sea floor structures and determine the permeability of the pathways so that they can be better constrained and quantified.

The team is also working closely with GEOMAR in Germany, the Lawrence Berkeley National Laboratoryin California, CGG in the UK, and Applied Acoustics in the UK. The project is complementary to the EU-funded Horizon 2020 project STEMM-CCS.

Aim

We will test the hypothesis that many chimney and pipe structures imaged on seismic reflection profiles in the North Sea represent
1. a fracture network that has been reactivated by pore fluid pressure which facilitates the migration of fluids upwards; and
2. shallow sub-seafloor lateral migration of fluids along stratigraphic interfaces and near-surface fractures.
We will conduct a novel geophysical experiment (WP1), calibrated and tested by rock physics experiments (WP2) which will provide information on the physical properties of the overburden both within and outside chimney structures. Specifically we will provide information on fracture density, orientation, whether fractures are open or closed, and derive permeability.
We will constrain and understand reactions with any leaking CO₂ by geochemical characterization of cores collected within a chimney structure (WP3) and reactive transport modelling (WP4).
We will model relevant and accurate scenarios of CO₂ leakage associated with likely carbon capture and storage sites in the North Sea by numerical modelling (WP4), which will synthesize information determined from the other work packages.

People

NOC people