Time-lapse imaging of CO2 migration within near-surface sediments during a controlled sub-seabed release experiment

The ability to detect and monitor any escape of carbon dioxide (CO2) from sub-seafloor CO2 storage reservoirs is essential for public acceptance capture (CCS) as a climate change mitigation strategy. Here, we use repeated high-resolution seismic reflection surveys acquired using chirp profiler mounted on an autonomous underwater vehicle (AUV), image gas released into shallow sub-surface sediments above potential CCS site at 120 m water depth in the North Sea. Observations temporal changes reflectivity, attenuation, unit thickness bulk permeability sediment were used develop four-stage model evolution migration marine sediments: Proto-migration, Immature Migration, Mature Pathway Closure. Bubble flow was initially enabled through propagation stable fractures but, over time, transitioned dynamic with associated step permeability. Once injection rate exceeded which could coarser overlying point, began pool along grain size boundary. This enhanced understanding free near-surface will help improve methods detection quantification subsurface sediments.