Dynamics of CO2 release from below the seafloor, mixing and environmental impacts - Annual report VISTA 2009

Annual report VISTA 2010

Dynamics of CO2 release from below the seafloor, mixing and environmental impact

Project director: Alendal, Guttorm, UoB

Post-doc/ scholar: Enstad, Lars Inge

Project duration: 01.04.2009 – 31.07.2011

Technical contact person in Statoil: Last name, First name

Division head: Mostad, Helle Britt

Project number: 6152

Object:

The main objective of this project is to clarify how CO₂ enters oceanic waters and subsequently dissolve and spread in the water column. This is to be done by comparing model data with existing data from observed natural analogues. Such natural analogues are until now only observed at the seafloor in volcanic areas where temperature and salinity gradients are high. To serve as a natural analogue the geological conditions are also quite different from what one would expect to find in an area with a potential to be used as a geological storage site for CO₂. Another known and observed form of gas leakage at the seafloor are hydrocarbons, mainly CH₄, seeping out in areas with pockmarks. These are found in hydrocarbon rich areas where the geological conditions are more similar to what one would expect to find at a storage site. Unfortunately the chemical properties of CH₄ is quite different from that of CO₂ in seawater. To be able to use natural occurrences of gas seepage as analogues it is important to identify the most suitable seepage sites and to use the appropriate model tools.

Status:

During the last six months the candidate has been on a sick leave for a period and has also been working on other projects. Due to this the current progress beyond the previous biannual report is limited. In October Nikolaus Bigalke and Gregor Rehder visited Bergen, and the final manuscript on rise velocity for droplets and bubbles was prepared for submission in connection with their visit. The code containing the coupling of a single droplet/bubble model and a the MIT general circulation model has been prepared for numerical testing. Also the single droplet/bubble model has been improved with additional solubility parametrizations based on published lab experiments. The single droplet/bubble model was tested against in situ experimental values. Further literature survey on occurrences of natural leakage of gases and liquids at the seafloor has also been performed.

Publications:

Conferences:

TCCS-4, Trondheim, October 2007, “Comparison of methane and carbon dioxide behavior in seawater: Lessons relevant to CO₂ leakage”, Oral presentation

Ocean in a high CO₂ world, Monaco, October 2008, “A numerical study of transport and spreading of gases from gas-seepage through the seafloor”, Poster presentation

GHGT9, Washington, November 2008, “A numerical study of transport and spreading from natural gas-seepage analogues through the seafloor”, Poster presentation

Publications:

«Natural seabed seeps, preparations for numerical studies», Enstad, L. I. , BCCS Technical Report Series, NO-22

“Dissolution of CO₂ from a CO₂ lake modeled using advanced vertical turbulence mixing scheme”, L. I. Enstad, K. Rygg, P. M. Haugan, G. Alendal, Greenhouse Gas Control, 2008

«Dissolution from a CO₂ lake», Enstad, L. I., Haugan, P. M. & Alendal G., Geochimica et Cosmochimica Acta 71 (15): A257-A257 Suppl. S, AUG 2007

“Terminal velocities of pure and hydrate coated CO₂ droplets and CH₄ bubbles rising in a simulated oceanic environment”, N. Bigalke, L. I. Enstad, G. Rehder & G. Alendal, to be submitted

“Simulating CO₂ transport into the ocean from a CO₂ lake at the seafloor using z- and σ- coordinate model”, K. Rygg, L. I. Enstad & G. Alendal, Ocean Dynamics, 2009