A step-by-step approach to creating and tuning PVT-models of reservoir hydrocarbon systems based on the state equation

The article is considering a new effective step-by-step approach to creating and tuning PVT-models of reservoir oil and reservoir gas condensate mixtures. The method is based on the reproducing of the results of field measurements and basic laboratory studies of representative samples in thermodynamic modeling using cubic three parameters equation of state. Tuning PVT-model is used for reliable modeling of PVT properties of reservoir fluids (reservoir oil and reservoir gas) in the design and monitoring of field development, calculation of multiphase flow in wells and field pipelines, as well as in basin modeling. Proposed approach makes possible to tune the PVT model with high accuracy of both reservoir oil and reservoir gas condensate system to experimental data using a step-by-step procedure, where at each step, by changing one of the parameters of the equation of state, one of the PVT properties of the hydrocarbon system is tuned. Algorithmization and automated application of this approach in specialized software products is possible. Proposed approach allows tune reservoir oil PVT-models on the main PVT-properties such as saturation pressure, FVF, STO density, gas-oil ratio of reservoir oil and dependencies of dynamic viscosity and compressibility on pressure at reservoir temperature as well as STO density. The tuned gas-condensate PVT-model precisely reproduces the key properties such as dew point pressure, initial condensate content in the reservoir gas, z-factor of the reservoir gas, gas-oil ratio, stable condensate density, drop down curve by the result of CVD-test. PVT-models created on the base of the proposed method, provide reliable information on the properties of a reservoir fluid in development of flow simulation both using a reservoir simulation compositional models and using pseudo models “black oil”. The method is illustrated by the example of creation of the adequate PVT-models of various regions of Russia reservoir oil and reservoir gas condensate mixtures.