Determination of Condensate Loss in the Presence of Nonhydrocarbon Components in Reservoir Gas

Introduction. Effective forecasting of development indicators and further exploitation of oil and gas condensate fields require operational data on the composition and properties of fluids. As part of the work, based on experimental PVT studies and analytical diagrams, the influence of non-hydrocarbon components on the thermodynamic processes of the reservoir mixture of the Mastakh field was determined. Different solubilities of heavy fractions of hydrocarbons in nitrogen and helium have been revealed. Materials and research methods The methodology for conducting thermodynamic studies and adjusting fluid dynamic properties using analytical diagrams can be divided into several stages: preparing recombined samples, conducting PVT experiments, processing research results. Using the methodology of Gazprom VNIIGAZ LLC, the influence of non-hydrocarbon components on condensate losses in the deposit was determined for the conditions of development of the Mastakhskoye field.

Research results and their discussion. The Mastakh gas condensate field is confined to the brachyanticlinal structure of the same name. It has a sublatitudinal strike along a closed isohypse. The arch is complicated by dome-shaped uplifts, the most significant of which are the western and eastern ones. The western rise has a fairly flat and extensive arch. The fault has not been opened in any of the wells. However, indirect signs indicate its presence.

The amount of undersaturation of the reservoir system is not high (1.15–1.3), high (up to 1.5) and depends mainly on the abnormally high reservoir pressure. Other reasons for this phenomenon may be the peculiarity of the formation conditions of the deposit or the shift of an already formed deposit. In addition, a significant thermodynamic characteristic is the dissolving ability of hydrocarbon and non-hydrocarbon components in the gas composition. For the initial conditions of the Mastakh field, a difference in reservoir pressures between the roof and the gas-water contact can be traced. There is a change in the content of hydrocarbon and non-hydrocarbon components over the area of the deposit.

Thus, as a result of comparing the experiments performed, it was established that the presence of nitrogen and helium in the mixture has different effects on the process of precipitation and loss of hydrocarbons in the deposit.

Conclusions. Thus, the data obtained made it possible to determine the influence of non-hydrocarbon components on condensate losses in the deposit and on changes in the properties of the gas condensate system during the development of the Mastakh field. The different degrees of solubility of condensate in the presence of nitrogen and helium, as well as their effect on reservoir losses of hydrocarbons at the stages of pressure reduction, were determined.

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