New correlations for density of methane-free sodium chloride brine and solubility of methane in sodium chloride brines, valid over wide ranges of pressure, temperature, and salinity, are presented. Both correlations agree with the best available measurements within experimental error over most of the range of validity. These new correlations are combined with published correlations for methane partial molar volume to provide accurate and internally consistent estimates of brine density, specific volume, formation volume factor, and coefficient of isothermal compressibility at pressures above or below the bubble point pressure. The brine density correlation is valid for temperatures from 0 to 275° C (32 to 527° F), pressures from 0.1 to 200 MPa (14.5 to 29,000 psi), and sodium chloride content from 0 to 6 moles/kg H 2 O (0 to 26% by weight). The methane solubility correlation is valid for temperatures from 20 to 360° C (68 to 680° F), pressures from 0.9 to 200 MPa (130 to 29,000 psia), and sodium chloride content from 0 to 6 moles/kg H 2 O (0 to 26% by weight). A modification of an existing correlation for brine viscosity is also presented, extending its range of applicability to temperatures between 20 and 300° C (68 to 572° F), pressures between 0.1 and 200 MPa, and salinity between 0 and 5.4 moles NaCl/kg H 2 O (0 to 25% NaCI by weight).