Purpose. Finding the connection between the thermodynamic conditions of hydrocarbon mixtures synthesis and zones of oil and gas accumulation. Methodology. The thermodynamic eguilibrium depths of gas and gas-condensate deposits were fixed by the method of eguilibrium constants of independent reactions based on the chemical composition of hydrocarbons re-counted on chemical elements. The investigations of formation waters, natural gases and water-dissolved gases were based on the methods of chemical, elementary spectral, atomic absorption and gas chromatographic analysis. Results.