CO₂ storage Environmental Baseline

A main concern and hazard associated with offshore CO₂ storage is leakage through the overburden sediments reaching the seabed and into the water column. We hypothesize that an early indicator of CO₂ leakage from a CCS reservoir will be increased methane in the surface sediments, with thermogenic/long chain molecular signatures. In the SEEP and SEABAS research studies, we have conducted a multiproxy study involving geophysical data identifying the pathways of possible seepage, microbial and gas data characterizing the present type of seepage and sedimentary data, variations in elements and fauna characterizing the past seepage history at a storage site. Hereby we have tested the possibilities for proxy-based identification and development of toolboxes for identifying both methane and CO₂ seepages in the abandoned reservoirs and at possible CO₂ storage sites in the Danish North Sea. We propose that such a comprehensive seabed baseline analyses based on multiple tools is carried out prior to storage.