As part of the Natural Environment Research Council (NERC) Characterisation of major overburden leakage pathways above sub-seafloor CO2 storage reservoirs in the North Sea (CHIMNEY) project, a broadband seismic anisotropy experiment was undertaken during RRS James Cook cruise JC152, over a subsea chimney structure in the northern North Sea around Scanner Pockmark, August to September 2017. The chimney structure was also drilled for core samples, which were subsequently analysed alongside synthetic rock samples in various on-shore laboratory experiments. Seismic data were acquired using sources including Bolt and GI airguns, and various sparkers. Data were recorded using multi-channel streamers and by a series of ocean bottom seismometers. The drilled rock samples were analysed at the National Oceanography Centre, Southampton (NOCS) Rock Physics Laboratory, and were compared with synthetic rock samples with aligned fractures. Data were quality controlled and processed by the JC152 Science Party. In conjunction with multi-beam bathymetry data acquired on the same cruise, these data enabled scientists to understand the surface and internal structure and origin of the chimney structure. This facilitated estimation of the permeability of the chimney and its surroundings, and enabled leakage pathways to be determined. The potential for past oil and gas reservoirs and saline aquifers to be used as Carbon Capture and Storage (CCS) reservoirs of atmospheric CO2 were subsequently explored. The safety of storing CO2 in such reservoirs is dependent on fully exploring the risks of any leakage from such chimney structures. CHIMNEY was funded by the Natural Environment Research Council (NERC) under grant reference NE/N016130/1, and involved scientists from the National Oceanography Centre, Southampton and the University of Edinburgh. Investigators worked closely with project partners at GEOMAR, Lawrence Berkley National Laboratory, CGG SA and Applied Acoustics Engineering Technologies Ltd . The project was complementary to the EU-funded Horizon 2020 project: Strategies for Environmental Monitoring of Marine Carbon Capture and Storage (STEMM-CCS).
