MEASURE OF THE HYDRATE-LIQUID-GAS PHASE BOUNDARY THERMODYNAMIC CONDITIONS FOR ETHANE WITHIN A PURE QUARTZ POROUS SAND: DIFFERENCES FROM THE IDEAL EQUILIBRIUM ASSOCIATED TO THE SEDIMENT

Small-chain hydrocarbons commonly included in natural gas mixtures, as ethane, may significantly intervene during the capture/release of methane and carbon dioxide in marine gas hydrate reservoirs. To establish the feasibility of CO<sub>2</sub>/CH<sub>4</sub> replacement in natural hydrate reservoirs, the role of those species needs to be carefully explored. This study preliminary deepened the production of pure ethane hydrates within porous quartz sediments, within a lab-scale equipment suitable for then carrying out replacement experiments. The production of C<sub>2</sub>H<sub>6</sub> hydrates was described in terms of induction time, pressure-temperature range of production, and moles of hydrates formed. The results obtained during dissociation were exploited to define the hydrate-liquid-gas boundary conditions of the system and compare them with the effective equilibrium conditions, in order to detect how the sediment intervened during the process. The self-preservation effect was quantified. Finally, the measured phase boundary values were collected and included in this study both numerically and graphically.