STANDARD PARTIAL MOLAL PROPERTIES OF AQUEOUS ALKYLPHENOLS AT HIGH PRESSURES AND TEMPERATURES

Abstract

Potential influences on the distribution of alkylphenols in oilfield waters include simple partitioning between oil, water, and solid phases, generation of alkylphenols during kerogen maturation in source rocks, and reactions at the oil-water interface in the oil reservoir. Assessment of whether reactions at the oil-water interface influence phenol distributions in basinal aqueous waters requires thermodynamic properties of the aqueous alkylphenols. In this study we have calculated standard partial molal thermodynamic properties of aqueous phenol and cresols at 25°C and estimated standard partial molal thermodynamic properties of aqueous xylenols at 25°C. These thermodynamic properties (Gibbs free energy, enthalpy, entropy, heat capacity, and volume) together with estimated coefficients for the revised Helgeson-Kirkham-Flowers (HKF) equations of state allow prediction of thermodynamic properties of reactions involving these species at high temperatures and pressures. Computed logarithmic equilibrium constants (log K) for hydration reactions involving alkylphenol are in close agreement with log K values calculated from published experimental data (Dohnal and Fenclova, 1995). Resulting thermodynamic properties may be used together with analytical results, to assess whether metastable equilibrium is a major influence on the abundance and distribution of alkylphenols in petroleum and associated water.