Chemical thermodynamics of hydrocarbon compositions in natural gas field, northeast of Thailand

Abstract

The phase envelope of hydrocarbon species in natural gas can be predicted by using thermodynamic simulation. Conceptual thermodynamics depends on physical and chemical characteristics in equilibrium condition. The API gravity of condensate is expressed in a range of 55–63°. Its average density is similar to the specific gravity of 0.74. Pressures in each gas processing process are decreased from the gas well (74.754 bar g) to the condensate tank (0.02 bar g). Mostly methane is discovered approximately 96 mol%. Due to physical and chemical properties, this petroleum reservoir indicates the dry gas reservoir. Chemical reactions depending on hydrocarbon compositions can be valuable for evaluating phase equilibrium. These chemical reactions based on hydrocarbon species are fabricated by chemical species as reactants and products. For creating them, all compositions related to the genesis of petroleum in the same environment are combined as a reactant. They are possibly defined as phase related to Gibbs free energy. Carbon dioxide, hydrogen, and nitrogen gas in petroleum reservoir are 10, 8, and 2 mol%, respectively. The chemical thermodynamics is simulated by using Prode Properties, a computer software program, in which Peng–Robinson equation of state is used as the chemical thermodynamic model. Characteristics of phase envelope consist of the critical temperature and pressure at phase transformation between liquid and gas. Two types of conceptual schemes are varying the invariable and variable mole fraction to evaluate the phase envelope. For their invariable mole fraction, the carbon ratio is defined at 60:20 percentages. Temperatures of natural gas from the phase envelope are inversely proportional to equilibrium constant. High temperature at low equilibrium constant specifies the forward chemical reaction. For their variable mole fraction, the increased carbon atoms affect to gradually intensify the temperature and pressure. Hydrocarbon types and mole fraction of these components concern to the possibility of phase envelope at suitable phase.