In this article, let's study about basic properties of oil and how it is defined.
Solution Gas-Oil Ratio
It is also called as "Solution GOR". It is defined as the amount of gas (in standard condition) that will dissolve in unit volume of oil when both are taken down to the reservoir at the prevailing pressure and temperature; that is,
The "standard condition" is defined as 14.7 psia and 60 degree Fahrenheit. At a given temperature, solution GOR remains constant at pressures above bubble-point pressure. It drops as pressure decreases in the pressure range below the bubble-point pressure.
Solution GOR is measured in PVT laboratories. Empirical corrleations are also available based on data from PVT labs. Usually these data are taken during well testing period of the well.
Density of Oil
It is defined as the mass of oil per unit volume. It is widely used in hydraulics calculations. Density of oil is pressure dependent due to the presence of gas content. The density of oil at standard condition (stock tank oil) is evaluated by API gravity. The relation ship between the density of stock tank oil and API gravity is given through the following relations:
The density of oil at elevated pressure and temperatures can be estimated on empirical correlations developed by a number of investigators. Ahmed (1989) gives a summary of correlations. Engineers should select and validate the correlations carefully with measurements before adopting any correlations.
Formation Volume Factor for Oil
It is defined as the volume occupied in the reservoir at the prevailing pressure and temperature by volume of oil in stock tank, plus its dissolved gas; that is,
Formation volume factor of oil is always greater than unity because oil dissolves more gas in reservoir condition than in stock tank condition. At a given reservoir temperature, oil formation volume factor remains nearly constant at pressures above bubble-point pressure. It drops as pressure decreases in the pressure range below the bubble-point pressure.
Viscosity of Oil
It is empirical parameter used for describing the resistance to flow of fluid. The viscosity of oil is of interest in well-inflow and hydraulics calculations in oil production engineering. While the viscosity of oil can be measured in PVT labs, it is often estimated using empirical correlations by a number of investigators.
Oil Compressibility
It is defined as
Oil compressibility is measured from PVT labs. It is often used in modeling well-inflow performance and reservoir simulation.
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