Open AccessMethane hydrate stability in pore water: A simple theoretical approach for geophysical applications
Author(s) -
Dickens Gerald R.,
QuinbyHunt Mary S.
Publication year - 1997
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/96jb02941
Subject(s) - hydrate , clathrate hydrate , methane , pore water pressure , electrolyte , dissociation (chemistry) , thermodynamics , salinity , geology , chemistry , geotechnical engineering , physics , organic chemistry , oceanography , electrode
Geophysicists have recently expressed an interest in understanding how pore water composition affects CH 4 hydrate stability conditions in the marine environment. It has previously been shown in the chemical engineering literature that CH 4 hydrate stability conditions in electrolyte solutions are related to the activity of water ( a w ). Here we present additional experimental data in support of this relationship and then use the relationship to address issues relevant to geophysicists. Pressure and temperature conditions of CH 4 hydrate dissociation were determined for 10 solutions containing variable concentrations of Cl − , SO 4 2− Br − , Na + , K + , Mg 2+ , NH 4 + , and Cu 2+ . The reciprocal temperature offset of CH 4 hydrate dissociation between the CH 4 ‐pure water system and each of these solutions (and for other electrolyte solutions in literature) is directly related to the logarithm of the activity of water (ln a w ). Stability conditions for CH 4 hydrate in any pore water system therefore can be predicted simply and accurately by calculating ln a w . The effect of salinity variation and chemical diagenesis on CH 4 hydrate stability conditions in the marine environment can be evaluated by determining how these processes affect ln a w of pore water.