Scholarly record

THE EFFECT OF USING A DIFFERENT POROUS MEDIUM FOR GAS HYDRATE PRODUCTION: A COMPARISON BETWEEN PURE QUARTZ SAND AND A NATURAL PRODUCT COMING FROM THE MEDITERRANEAN SEABED.

Albert Gambelli, Federico Rossi

Abstract

The gas hydrate formation is a non-stoichiometric process, which may be affected by a great number of variables, rather than thermodynamic conditions. Several chemical additives were found to act as inhibitors or promoters (or both together under specific situations) for gas hydrate. The most known chemical inhibitor is sodium chloride, whose effects needs to be widely investigated, due to its presence in about 97% of discovered hydrate reservoirs. However, other elements may intervene on the formation process and cause a delay or an acceleration of its occurrence. The present work focused on effect associated to the use of different porous medium to host gas hydrate formation. Gas hydrate are widespread in world oceans and are also present in the Mediterranean Sea. While thermodynamic conditions are often similar, seabed characteristics strongly vary among all reservoirs. The way in which a specific sand affects the hydrate formation might be extremely useful to forecast the feasibility of a CO2/CH4 exchange process into natural gas hydrate reservoirs. Here two different typologies of sand were tested: a classical quartz sand, which is often used for its neutrality as concerns the formation process and a silica-based sand containing several compounds known as potential inhibitors or promoters. This second product comes from the Tunisian costs (Mediterranean Sea) and its characteristics (composition, granulometry, porosity and so on) were not thought to favour hydrate formation. Two different guests were tested: methane and carbon dioxide. For both compounds three tests were made in quartz sand and three others in the other medium. Results in terms of hydrate formation and time duration of the process were finally compared.

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