Мethodology for calculation of phase behavior of a natural hydrocarbon system with account of formation water mineralization

The development of gas condensate fields requires the prediction of phase behavior. The existing models do not consider the presence of several roots of material balance equation and water mineralization. Therefore, the aim of the work is to develop the methodology for calculation of phase state of a gas condensate mixture, considering the determination of all the roots of the material balance equation and mineralization of reservoir water. For the first time, the number of roots of the material balance equation is determined using Sturm’s theorem. The object of the study is a reservoir containing a gas condensate mixture. The paper develops the methodology for calculation of phase behavior of a multicomponent hydrocarbon system. Unlike the traditional algorithm, this methodology involves the Sechenov equation. The molar fraction of the gas phase is found using Sturm’s theorem and the algorithm of sequential division of Euclidean polynomials. The calculation results for the model object indicate that the molar fraction of the gas phase is more than 32 %. The distribution of the components over the phases is obtained. The effect of temperature, pressure, and salinity of water on the molar fraction of the gas phase has been researched. Based on calculations for the model object, it was found that the region of the two-phase state corresponds to a narrow range of reservoir pressures. As the pressure increases, the molar fraction of the gas phase decreases due to the transition of the system to a liquid state.