Présentations Colloques

Oral Presentation
Session 8.08: Mineral and Thermal water: an indicator of deep processes and source of economically valuable minerals
Porowski Adam
Origin of Methane in Edge Oil-field Mineral Waters of the Iwonicz ZdrÓj Spa, Central Carpathian Synclinorium, SE Poland.
Mineral edge oil-field waters are extracted for curative and drinking purposes by several wells and springs within the Iwonicz anticline, which is one the several fold structures of the Central Carpathian Synclinorium, SE Poland. The waters extracted in the Iwonicz Zdrój spa are mainly Cl-HCO3-Na type, with total mineralization from 7 to 19 g L, rich in Br and I, and first of all in CH4 and CO2 in gas phase. Differentiation of CH4 sources is based on isotopic techniques which involves measurement isotopic ratio of both carbon and hydrogen within methane and related compounds such as higher hydrocarbons (if present), isotopic composition of associated carbon dioxide and water. For this study samples of gas phase (CH4 and CO2) and water have been collected from 8 wells used by spa. The isotopic composition of methane ranged from -67‰ to -47‰ and -249‰ to -202‰, for carbon and hydrogen respectively. This suggests that CH4 is associated with early maturation processes or originate from mixed source, both thermogenic and or bacterial processes. Positive correlation of +13CCH4 with depth strongly suggest that thermogenic methane is a major fraction of gas phase and the bacterial contribution may increase in shallow wells. Obtained isotopic composition of CH4 may also be a result of pure bacterial activities which produce methane combined with succeeding isotopic alterations via CH4 oxidation and other reaction during methane degassing. Calculated fractionation factor α+13C between coexisting CH4 and CO2 in water in the range of 1.06 – 1.09 indicates that CO2 reduction is the dominant methanogenic pathway.