Xuqiang Guo

Equation of state analog correlations for the viscosity and thermal conductivity of hydrocarbons and reservoir fluids

Abstract Based on the geometric similarity of P–V–T, T–μ–P and T–λ–P diagrams, viscosity (μ) and thermal conductivity (λ) data of hydrocarbons and their mixtures have been successfully correlated using a cubic equation of state (EOS) type equation. The advantages of using EOS-analog expressions are simple in form, applicable to both gas/liquid, high-pressure/low-pressure, and smooth phase transition of μ and λ in the near-critical region could be achieved. First, a modified viscosity correlation based on PR (Peng–Robinson) EOS type expression is presented, which improves the prediction of the viscosity of reservoir fluids (including CO2-injected enhanced oil recovery systems). Then, the development of EOS type expression for fluid thermal conductivity is described. The results of extensive tests with data indicate the superiority of the proposed EOS-analog viscosity and thermal conductivity correlations over typical empirical and semi-empirical correlations used in the petroleum industry.

Viscosity model based on equations of state for hydrocarbon liquids and gases

Based on the similarity between P-v-T and T-μ-P relationships, viscosity (μ) models for pure hydrocarbons (mainly for n -alkanes) have been developed from the three-parameter Patel-Teja (PT) and two-parameter Peng-Robinson (PR) cubic equations of state. The EOS-based viscosity models are applicable to both liquid and gas phases, and have been successfully extended to hydrocarbon mixtures containing defined components as well as undefined C 7 + -fraction. Compared to the typical viscosity correlations widely used in the petroleum industry, significant improvement in prediction accuracy was achieved. Since the P-v-T , V-L-E and viscosity calculations can be performed by using a single equation of state, the thermodynamic consistency of reservoir simulation and process simulation calculations is improved.

EXPERIMENTAL DETERMINATION OF METHANE HYDRATE FORMATION IN THE PRESENCE OF AMMONIA

Formation condition data for methane hydrate in ammonia + water and ammonia + water + tetrahydrofunan (THF) systems are very important for the process development and the determination of operation condition for recycling the vent gas of ammonia synthesis using hydrates. This paper focused on the formation conditions of methane hydrate in the presence of NH3 + H2O and NH3 + H2O + THF system. Equilibrium data of methane hydrate in the temperature, pressure and concentration ranges from 277 to 291 K, 0 to 8 MPa, 1 to 5 % ammonia, were obtained. The experimental results indicate that ammonia has an inhibitive effect on hydrate formation. The higher the concentration of ammonia is, the higher the formation pressure for methane hydrate will be.