Determination and prediction of reservoir oil physical parameters by semigraphical method for the Inner zone of Carpathian Foredeep

Abstract

The prediction of the phase state of hydrocarbons at great depths in the area of high temperatures and pressures is of particular relevance today. The peculiarity of the current forecasts is that the pressure-and-temperature conditions of the occurrence and the physical parameters of the reservoir oils are considered as combined average values in a single, integral Inner Zone of the Pre-Carpathian Depression. The specificity of changing each of them is also the same and is forced to extend to the entire territory of the zone. The article considers an important issue of substantiation of a new, more detailed forecast. It is necessary to be able to pre-dict the basic characteristics and phase state of reservoir oils depending on the depth of occurrence in different parts of the Inner Zone. The article considers the possibility of determining the physical parameters of formation hydrocarbon fluids by grapho-analytical method only when there are results of the research of wells at steady and unstable regimes. The developed method allows to quickly determine the set of physical parameters of reservoir oils: saturation pressure, overpressure value, gas content, average gas solubility coefficient, reservoir density, volume factor and oil shrinkage, conversion shrinkage factor, compressibility and thermal expansion factor, the distribution of fluid mass into liquid and gas phases under standard surface conditions and under the condition of fluid evaporation. The calculated equations are based on the use of universal thermodynamic quantity – the molecular weight of the hydrocarbon system. Being the function of only this component composition of the system, the molecular weight does not depend on pressure and temperature. This method allows to estimate the opera-tional stocks of fluids immediately after receiving industrial inflows in the first well, i.e. before the complex of laboratory studies.