• Energy Research

In this work the dynamics and dissolution of a hydrate‐covered CO2 drop were studied, using a numeric model and data from one of very few CO2 experiments performed in the real ocean. A theory including the standard drag curve of rigid spheres was shown not to fit the observed drop rise velocity. However, a drag parameterization supported by numerous laboratory experiments with gas bubbles provides a good match of the observed rise velocity of a liquid CO2 drop covered with hydrate. The results confirm laboratory results showing that shape is a key factor determining the CO2 drop dynamics. We also found that hydrate reduces the mass transfer of the observed drop by a factor of 2, which is compatible with laboratory experiments. Numerical experiments with different drop sizes showed that the choice of drag parameterization has a significant impact on the estimated vertical distribution of dissolved CO2.

In this work the dynamics and dissolution of a hydrate‐covered CO2 drop were studied, using a numeric model and data from one of very few CO2 experiments performed in the real ocean. A theory including the standard drag curve of rigid spheres was shown not to fit the observed drop rise velocity. However, a drag parameterization supported by numerous laboratory experiments with gas bubbles provides a good match of the observed rise velocity of a liquid CO2 drop covered with hydrate. The results confirm laboratory results showing that shape is a key factor determining the CO2 drop dynamics. We also found that hydrate reduces the mass transfer of the observed drop by a factor of 2, which is compatible with laboratory experiments. Numerical experiments with different drop sizes showed that the choice of drag parameterization has a significant impact on the estimated vertical distribution of dissolved CO2.

Abstract Carbon capture and storage is key for mitigating greenhouse gas emissions, and offshore geological formations provide vast CO2 storage potential. Monitoring of sub-seabed CO2 storage sites requires that anomalies signifying a loss of containment be detected, and if attributed to storage, quantified and their impact assessed. However, monitoring at or above the seabed is only useful if one can reliably differentiate abnormal signals from natural variability. Baseline acquisition is the default option for describing the natural state, however we argue that a comprehensive baseline assessment is likely expensive and time-bound, given the multi-decadal nature of CCS operations and the dynamic heterogeneity of the marine environment. We present an outline of the elements comprising an efficient marine environmental baseline to support offshore monitoring. We demonstrate that many of these elements can be derived from pre-existing and ongoing sources, not necessarily related to CCS project development. We argue that a sufficient baseline can be achieved by identifying key emergent properties of the system rather than assembling an extensive description of the physical, chemical and biological states. Further, that contemporary comparisons between impacted and non-impacted sites are likely to be as valuable as before and after comparisons. However, as these emergent properties may be nuanced between sites and seasons and comparative studies need to be validated by the careful choice of reference site, a site-specific understanding of the scales of heterogeneity will be an invaluable component of a baseline.

Abstract Carbon capture and storage is key for mitigating greenhouse gas emissions, and offshore geological formations provide vast CO2 storage potential. Monitoring of sub-seabed CO2 storage sites requires that anomalies signifying a loss of containment be detected, and if attributed to storage, quantified and their impact assessed. However, monitoring at or above the seabed is only useful if one can reliably differentiate abnormal signals from natural variability. Baseline acquisition is the default option for describing the natural state, however we argue that a comprehensive baseline assessment is likely expensive and time-bound, given the multi-decadal nature of CCS operations and the dynamic heterogeneity of the marine environment. We present an outline of the elements comprising an efficient marine environmental baseline to support offshore monitoring. We demonstrate that many of these elements can be derived from pre-existing and ongoing sources, not necessarily related to CCS project development. We argue that a sufficient baseline can be achieved by identifying key emergent properties of the system rather than assembling an extensive description of the physical, chemical and biological states. Further, that contemporary comparisons between impacted and non-impacted sites are likely to be as valuable as before and after comparisons. However, as these emergent properties may be nuanced between sites and seasons and comparative studies need to be validated by the careful choice of reference site, a site-specific understanding of the scales of heterogeneity will be an invaluable component of a baseline.

AbstractNatural leakages of CO2 are reported in the literature at mid ocean ridges and CH4 seepages in hydrocarbon rich ares. These could potentially serve as natural analogues of leakages from CO2 storages. In this study we have developed a model tool for the rise and dissolution of droplets or bubbles of these gases and the subsequent spreading of the compounds. The preliminary results shows some of the same trends as has been reported on observations from natural gas leakages. The model has been setup for an idealized natural CO2 leakage in the deep ocean to illustrate how the model can represent such a leakage.

AbstractNatural leakages of CO2 are reported in the literature at mid ocean ridges and CH4 seepages in hydrocarbon rich ares. These could potentially serve as natural analogues of leakages from CO2 storages. In this study we have developed a model tool for the rise and dissolution of droplets or bubbles of these gases and the subsequent spreading of the compounds. The preliminary results shows some of the same trends as has been reported on observations from natural gas leakages. The model has been setup for an idealized natural CO2 leakage in the deep ocean to illustrate how the model can represent such a leakage.