f Core scale experiments for CO2-water- rock interaction in well cement and caprock

The injection of CO2 into CH4 hydrate bearing sediments may enable integration of CO2 storage with production from CH4 hydrates. In this study both liquid and gaseous CO2 was injected into the CH4 hydrate bearing sediments. Interaction of gaseous CO2 and CH4 hydrate was observed within the unconsolidated sand pack system that includes 30% CH4 hydrate saturation at free CH4 excess conditions. After the CO2 injection, cyclic behaviors at the pressure gauges were observed for approximately 6 hours that may indicate CH4-CO2 swap within hydrate cages. Swap process was confirmed by estimating the gas compositions at the instant of CO2 injection and by measuring gas concentration via gas chromatograph after the swap process. As a result of the swap process, it is estimated that %86.3 of the CO2 went into the hydrate phase. After stabilization, system was left to dissociate for several days and samples taken from the cell at different time intervals were analyzed via gas chromatograph in order to gain an insight on hydrate distribution in porous media after the swap process. Furthermore, interaction of liquid CO2 and CH4 hydrate was investigated within the unconsolidated sand pack system which includes certain amount of CH4 hydrate at water excess conditions. After the CO2 injection, cyclic behaviors at the pressure gauges were observed for approximately 3 days that may indicate CH4-CO2 swap within hydrate cages. In addition, swap process was verified via gas chromatography tests. At the instant of CO2 injection the mole fraction of CO2 in the system was 1 since all the CH4 was assumed to be converted to hydrate phase. After the swap process and stabilization of the system, sample taken from the cell was analyzed and result showed that mole fraction of CO2 in the cell is about 0.66 that suggests swap within hydrate cages. Then, system was left to dissociate for several hours and samples taken from the cell at different time intervals were analyzed via gas chromatograph in order to gain an insight on hydrate distribution in porous media after the swap process. The results obtained from these experiments propose that the injected CO2 causes dissociation of CH4 hydrate.