Advances in Deep-Ocean CO2 Sequestration Experiments

Abstract

This chapter reports on advances made in carrying out small-scale experiments on the direct injection of CO2 in the deep ocean using ROV technology. A carbon-fiber composite accumulator of 56L internal capacity for safe CO2 containment and delivery has been developed, and has been used for a series of experiments at 3600m ocean depth, thus enabling delivery of sufficient CO2 for biological response studies. A time-lapse camera for recording events associated with the CO2 pool has also been developed. A newly developed laser Raman spectrometer has been used to obtain spectroscopic information in situ, thus enabling detection of the state of the CO2, and the fate of impurities. CO2 dissolution rate of 1.7μmol/cm2/sec was measured by direct insertion of a pH probe into the liquid surface, thereby forming a pocket of water. This technique provides confirmation of the very rapid re-building of the hydrate skin in which surface cracks are quickly annealed. The presence of a hydrate skin exerts a strong effect on CO2 chemical and physical properties, and it has been observed quasi-chaotic instabilities associated with this phenomenon in which a transformation from thin film to massive hydrate formation has occurred within a few hours.