Novel techniques for seabed monitoring of CO2 leakage and monitoring campaigns based on reservoir, cap rock and overburden migration models

Prokaryotic communities rapidly respond to changes in the environment by altered abundances, changed community composition as well as shifted metabolic potential. Leakages from CO2 stored in deep sub surface geological formation under the seafloor can bring about changes in overlaying marine sediments that will affect residing prokaryotic communities. The COVERALL project aimed to develop and verify high resolution gene-based monitoring techniques for CO2 leakage based on molecular signatures of prokaryotic communities and to develop three conceptual leakage models to estimate possible CO2 leakage from reservoirs to the seafloor. The project has used and generated data from a combination of temporal and spatial gradients of in-situ and ex-situ CO2 release experiments of marine sediments, simulating leakages from sub seafloor CO2 storage sites. One of the main aims with the ex-situ experiment was to identify where the CO2 ends up after a leakage and how this affects oxygen and pH in overlying marine sediments. Preliminary results show that sediment properties change quickly after a leakage. The prokaryotic communities in marine sediments have been studied using high throughput sequencing of amplicons (16S rRNA), metagenomic and metatranscriptomic data. A bioinformatic gene detector workflow have been developed and utilized to detect CO2 anomaly signatures from the prokaryotic communities. We have generated vast amounts of data of 16S rRNA, metagenome and metatranscriptome from the experiments and successfully developed a gene-detector to identify genes that responds to increased amounts of CO2 in the sediment. The results show that the prokaryotic communities in the investigated marine sediments are complex and that a range of factors in addition to CO2 seem to strongly contribute to observed structure of the communities. So far, we have not been able to identify potential candidate-taxa or genes for CO2 monitoring in our data, and have also not been able to verify taxa previously described as candidate-taxa for CO2 monitoring in the literature. Modelling of CO2 migration through the sediments has helped us understand characteristics during CO2 leakages. An opinion paper written by the consortium on using prokaryotes for CO2 monitoring and CCU have been published in Trends in Biotechnology, and four papers with results from the in-situ and ex-situ CO2 release experiment are currently in preparation. In addition, we have one paper and one report currently being written up for the modelling-part. Althogether, we expect six scientific papers in international peer-rewieved journals and one report from this project.

The project team with partners from United Kingdom (UK), Greece (G) and Norway (N) proposes to use the Next Generation Technology of metagenomics and bioinformatic, for offshore post injection and long-term monitoring of CO2 storage sites. DNA extracted f rom seafloor sediments exposed to in situ CO2 release at the Scottish west coast will be analysed and compared to our existing CO2 anomaly signatures from the North Sea. An automatic workflow for fast finding and precise detection of genes associated with prokaryotic CO2 assimilation will be generated. Correlation analysis of geochemical parameters and genetic anomalies in in situ and ex situ CO2 exposed sediments will be made. To be able to estimate the resolution and sampling frequency required for safe long term monitoring of CO2 storage sites, we will calculate the theoretical migration of CO2 to the seabed from a conceptual storage site model with cap rock leakage. Based on this approach we will suggest monitoring campaigns and recommendations for th e conceptual storage site model and estimate the monitoring costs. The CCS community needs a technique able to detect deviations from baseline conditions in the seafloor in good time before CO2 migrates from the seafloor into the sea water where pelagic o rganisms such as fish can be affected.