Behaviors of CO₂ Hydrate Formation in the Presence of Acid-Dissolvable Organic Matters

Abstract

Carbon storage in the form of solid hydrate under seafloor has been considered to be promising for greenhouse gas control. Yet, open issues still remain on the role of the organic matters abundant in marine environments in the kinetics of hydrate formation; of particular interest is the involvement of the acid-dissolvable organic matters accompanying the acidification upon CO₂ injection. In this work, the CO₂ hydrate formation in the presence of the organic matters was <i>in-situ</i> monitored through the low-field nuclear magnetic resonance technique. It was found that the organic matters could kinetically promote the formation of CO₂ hydrate; this effect was further enhanced by the sulfur-containing acid-dissolvable organic matters. Water in the large pores was preferentially consumed; the following water conversion facilitated by the organic matters would result in a fragmentation of the large pores into separated small pores isolated by the hydrate clusters. Consequently, a further enhancement of the gas-water contact is suggested as the existence of substantial hydrate patches could act as a mass transfer barrier. Our findings expand our understandings on the kinetics of CO₂ hydrate formation in the presence of the organic matters and indicate the stability zone of gas hydrate a kinetically favorable geological setting for CO₂ sequestration.