Cruise Report RRS James Cook 152 - JC152: CHIMNEY – Characterisation of major overburden pathways above sub-seafloor CO2 storage reservoirs in the North Sea. Scanner and Challenger Pockmark Complexes

Cruise JC152 collected the major data sets for the CHIMNEY (Characterisation of major overburden leakage pathways above sub-seafloor CO2 storage reservoirs in the North Sea) NERC highlight topics research programme. The cruise investigated the Scanner and Challenger pock marks in the northern North Sea, which were previously known to be the locations of vigorous Methane venting. The cruise objectives were to collect data that could be used to constrain the geometry and internal structures of fluid flow, “Chimney” structures, with the eventual aim of determining the current permeability of the sub-surface. The cruise successfully completed two anisotropy experiments over the Scanner and Challenger pock marks by shooting various seismic sources into a grid of 25 and 7 ocean bottom seismometers respectively. Five different seismic sources (Bolt airguns, GI guns, Squid surface sparker, Duraspark surface sparker, and Deep Tow Sparker) were recorded by the ocean bottom seismometers, and an acoustic recorder deployed c. 25 m above the seabed. Multichannel seismic reflection profiles were collected with GI guns and both surface sparker sources, and single channel seismic reflection profiles were collected with the Deep Tow Sparker source. Single and multibeam echo sounder data were collected along all seismic profiles