A model to predict phase equilibrium of CH4 and CO2 clathrate hydrate in aqueous electrolyte solutions

Abstract A thermodynamic model to predict phase equilibrium of methane and carbon dioxide hydrate in aqueous electrolyte solutions is presented. Using the Pitzer model to account for the variation of water activity due to electrolytes and dissolved gas in aqueous solutions, we extended the model based on ab initio molecular potential developed recently by us for the CH4-H2O and CO2-H2O binary systems to the CH4 (or CO2)-H2O-salts system. Comparison of the model with extensive experimental data indicates that this model can accurately predict the phase equilibrium of CH4 hydrate and CO2 hydrate in various electrolyte solutions (such as aqueous NaCl, KCl, CaCl2, NaCl + KCl, NaCl + CaCl2 solutions, and seawater) from zero to high ionic strength (about 6 m) and from low to high pressures.

[1]  N. Møller,et al.  The prediction of mineral solubilities in natural waters: The Na-K-Mg-Ca-H-Cl-SO4-OH-HCO3-CO3-CO2-H2O system to high ionic strengths at 25°C , 1984 .

[2]  M. Kharrat,et al.  Experimental determination of stability conditions of methane hydrate in aqueous calcium chloride solutions using high pressure differential scanning calorimetry , 2003 .

[3]  G. Dickens,et al.  Methane hydrate stability in pore water: A simple theoretical approach for geophysical applications , 1997 .

[4]  John H. Weare,et al.  The prediction of methane solubility in natural waters to high ionic strength from 0 to 250°C and from 0 to 1600 bar , 1992 .

[5]  Kenneth S. Pitzer,et al.  Thermodynamics of electrolytes. IV. Activity and osmotic coefficients for mixed electrolytes , 1974 .

[6]  Carolyn A. Koh,et al.  Clathrate hydrates of natural gases , 1990 .

[7]  J. Vlahakis.  The Growth Rate of Ice Crystals : The Properties of carbon dioxide hydrate ; a review of properties of 51 gas hydrates , 1972 .

[8]  Gerald D. Holder,et al.  Thermodynamic and Molecular Properties of Gas Hydrates from Mixtures Containing Methane, Argon, and Krypton , 1980 .

[9]  B. Herzhaft,et al.  The stability of methane hydrates in highly concentrated electrolyte solutions by differential scanning calorimetry and theoretical computation , 2004 .

[10]  T. Maekawa.  Equilibrium conditions for gas hydrates of methane and ethane mixtures in pure water and sodium chloride solution , 2001 .

[11]  Kenneth S. Pitzer,et al.  Thermodynamics of electrolytes. III. Activity and osmotic coefficients for 2–2 electrolytes , 1974 .

[12]  Yigang Zhang,et al.  Experimental determination of the compositional limits of immiscibility in the system CaCl2H2OCO2 at high temperatures and pressures using synthetic fluid inclusions , 1989 .

[13]  Donald B. Robinson,et al.  The Measurement and Prediction of Hydrate Formation in Liquid Hydrocarbon-Water Systems , 1976 .

[14]  P. Englezos.  Computation of the Incipient Equilibrium Carbon Dioxide Hydrate Formation Conditions in Aqueous Electrolyte Solutions , 1992 .

[15]  Cor J. Peters,et al.  Occurrence of methane hydrate in saturated and unsaturated solutions of sodium chloride and water in dependence of temperature and pressure , 1983 .

[16]  John H. Weare,et al.  The prediction of borate mineral equilibria in natural waters: Application to Searles Lake, California , 1986 .

[17]  P. Englezos,et al.  Prediction of gas hydrate formation conditions in aqueous electrolyte solutions , 1988 .

[18]  Gerald D. Holder,et al.  Model for gas hydrate equilibria using a variable reference chemical potential: Part 1 , 2002 .

[19]  G. Dickens,et al.  Methane hydrate stability in seawater , 1994 .

[20]  B. Tohidi,et al.  Hydrate-free zone for synthetic and real reservoir fluids in the presence of saline water , 1997 .

[21]  H. D. Holland.  The chemistry of the atmosphere and oceans , 1978 .

[22]  T. Guo,et al.  Extension of the Patel—Teja equation of state to the prediction of the solubility of natural gas in formation water , 1991 .

[23]  J. Dubessy,et al.  Modelling of phase equilibria involving mixed gas clathrates; application to the determination of molar volume of the vapour phase and salinity of the aqueous solution in fluid inclusions , 1992 .

[24]  John H. Weare,et al.  An equation of state for the CH4-CO2-H2O system: I. Pure systems from 0 to 1000°C and 0 to 8000 bar , 1992 .

[25]  B. Tohidi,et al.  Modelling single and mixed electrolyte solutions and its applications to gas hydrates , 1995 .

[26]  Jerry P. Greenberg,et al.  The prediction of mineral solubilities in natural waters: A chemical equilibrium model for the Na-K-Ca-Cl-SO4-H2O system to high concentration from 0 to 250°C , 1989 .

[27]  Kenneth S. Pitzer,et al.  Thermodynamics of electrolytes. V. effects of higher-order electrostatic terms , 1975 .

[28]  N. Kalogerakis,et al.  EQUILIBRIUM CONDITIONS FOR METHANE HYDRATE FORMATION IN AQUEOUS MIXED ELECTROLYTE SOLUTIONS , 1991 .

[29]  Kenneth S. Pitzer,et al.  Thermodynamics of electrolytes. I. Theoretical basis and general equations , 1973 .

[30]  John H. Weare,et al.  The prediction of mineral solubilities in natural waters: A chemical equilibrium model for the NaKCaMgClSO4H2O system at temperatures below 25°C , 1990 .

[31]  Gerald D. Holder,et al.  A generalized model for predicting equilibrium conditions for gas hydrates , 1985 .

[32]  Kenneth S. Pitzer,et al.  A thermodynamic model for aqueous solutions of liquid-like density , 1987 .

[33]  E. D. Sloan,et al.  The effect of pressure on methane hydration in pure water and sodium chloride solutions , 2001 .

[34]  L. Diamond.  Salinity of multivolatile fluid inclusions determined from clathrate hydrate stability , 1994 .

[35]  Nicolas Kalogerakis,et al.  Equilibrium conditions for carbon dioxide hydrate formation in aqueous electrolyte solutions , 1993 .

[36]  Kenneth S. Pitzer,et al.  Thermodynamic Properties of Aqueous Sodium Chloride Solutions , 1984 .

[37]  Chen Hsiao-Sheng,et al.  The properties of the hydrates of chlorine and carbon dioxide , 1975 .

[38]  K. Pitzer,et al.  Thermodynamics of electrolytes. II. Activity and osmotic coefficients for strong electrolytes with one or both ions univalent , 1973 .

[39]  C. Monnin,et al.  The influence of pressure on the activity coefficients of the solutes and on the solubility of minerals in the system Na-Ca-Cl-SO4-H2O to 200°C and 1 kbar and to high NaCl concentration , 1990 .

[40]  P. Bishnoi,et al.  Prediction of carbon dioxide gas hydrate formation conditions in aqueous electrolyte solutions , 1994 .

[41]  N. Møller,et al.  The prediction of mineral solubilities in natural waters: A chemical equilibrium model for the Na-Ca-Cl-SO4-H2O system, to high temperature and concentration , 1988 .

[42]  R. Kobayashi.  Gas hydrate formation with brine and ethanol solutions , 1951 .

[43]  P. Collins.  Gas hydrates in CO 2 -bearing fluid inclusions and the use of freezing data for estimation of salinity , 1979 .

[44]  Lawrence B. Evans,et al.  A local composition model for the excess Gibbs energy of aqueous electrolyte systems , 1986 .

[45]  M. Cathelineau,et al.  Improvements in clathrate modelling: I. The H2O-CO2 system with various salts , 1996 .

[46]  Peter Englezos,et al.  Phase equilibrium data on carbon dioxide hydrate in the presence of electrolytes, water soluble polymers and montmorillonite , 1994 .

[47]  J. M. Prausnitz,et al.  Dissociation Pressures of Gas Hydrates Formed by Gas Mixtures , 1972 .

[48]  Zhenhao Duan,et al.  An improved model calculating CO2 solubility in pure water and aqueous NaCl solutions from 273 to 533 K and from 0 to 2000 bar , 2003 .

[49]  R. Spencer.  The prediction of mineral solubilities in natural waters : A chemical equilibrium model for the Na-KCa-Mg-ClS 04-Hz 0 system at temperatures below 25 OC * , 2022 .

[50]  Allen J. Barduhn,et al.  The properties of some new gas hydrates and their use in demineralizing sea water , 1962 .

[51]  L. Diamond.  Stability of CO2 clathrate hydrate + CO2 liquid + CO2 vapour + aqueous KCl-NaCl solutions: Experimental determination and application to salinity estimates of fluid inclusions ∗ , 1992 .

[52]  Kenneth S. Pitzer,et al.  Thermodynamics of concentrated electrolyte mixtures and the prediction of mineral solubilities to high temperatures for mixtures in the system Na-K-Mg-Cl-SO4-OH-H2O , 1987 .

[53]  Zhenhao Duan,et al.  Prediction of CH4 and CO2 hydrate phase equilibrium and cage occupancy from ab initio intermolecular potentials , 2005 .

[54]  E. Stenby,et al.  Prediction of high-pressure gas solubilities in aqueous mixtures of electrolytes , 1991 .

[55]  K. Pitzer,et al.  Thermodynamics of electrolytes. VI. Weak electrolytes including H3PO4 , 1976 .