Chemical Species Prediction for Development of Phase Behaviors of Natural Gas in Dry Gas Reservoir

Natural gas in a Natural Gas Field, a dry gas reservoir, northeast region of Thailand was investigated to determine the relationship of chemical species in order to predict phase behaviors using the thermodynamic simulation. Phase diagrams related to temperature (T) and pressure (P) dominate the phase behaviors of natural gas in the subsurface. The sub-chemical reactions were assumed by chemical relationships of their components which were similar to the chemical compositions of natural gas. Diagrams were generated from the thermodynamics simulation based on Peng-Robinson model combined with the Prode Properties program. Critical points as a function of mole fraction of methane were obtained by the phase envelope. Pressures at these critical points are mostly proportional to the increasing mole fraction of methane. The pseudocritical properties of temperature and pressure are related to the specific mole fraction of methane. Equilibrium conditions at this point are equivalent to methane mass. Pressures have more influence on methane (in reactant) at all chemical reactions. At approximately 0.75 mol fraction of methane, the P and T are limited with less than 22 MPa.a and 350 K, respectively. These associations are beneficial for predicting and controlling the phase behaviors in the petroleum reservoir.