The prediction of methane solubility in natural waters to high ionic strength from 0 to 250C and from 0 to 1,600 bar

A model for the solubility of methane in brines (0-6 m) for temperatures from 0 to 250C and for pressures from 0 to 1,600 bar (or slightly above) is presented. The model is based on Pitzer phenomenology for the liquid phase and a highly accurate equation of state recently developed for the vapor phase. Comparison of model predictions with experimental data indicates that they are within experimental uncertainty. Most experimental data sets are consistent within errors of about 7%. Although the parameters were evaluated from binary and ternary data, the model accurately predicts methane solubility in much more complicated systems like seawater and Salton geothermal brines. Application to fluid inclusion analysis is discussed. Minimum trapping pressures are calculated given the composition and homogenization temperature.