The mast successful empirical method for predicting hydrate-phase equilibrium in water-hydrocarbon system is based upon vapor-solid equilibrium ratio (K-vs values) correlations. Equilibrium ratio charts for known hydrate formers, with n-butane as the heaviest compound, are available in the literature. With the discovery of heavier hydrate-forming compounds, their equilibrium ratio charts are required for reliable prediction of the hydrate-free zone of hydrocarbon mixtures, particularly reservoir fluids. In this work, an in-house thermodynamic model, validated against experimental hydrate equilibrium data of four structure-II heavy hydrate formers (HHF), benzene, cyclopentane, cyclohexane, and neopentane, has been used for generating their K-vs value charts. The resulting K-vs values have been used in predicting a hydrate-free zone of binary and ternary mixtures of HHF with methane and/or nitrogen, demonstrating success when compared with experimental data.