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 CO2 / CH4 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 C2 H6 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.