Propierties of petroleum fluid

Ideal gas propierties:

The volume occupied by the molecules is insignificant with respect to the occupied by the gas

There are no attractive or repulsive forces between the molecules or between the molecules and the walls of the container.

All collisions of molecules are perfectly elastic, that is, there is no loss of internal energy upon collision.

Boyle’s equation

Boyle observed that the volume of an ideal gas is inversely proportional to pressure for a given mass of gas when temperature is maintained constant.

V= 1/p

Charles’ equation

The volume of an ideal gas is directly proportional to temperature for a given mass of gas when pressure is maintained constant.

V/T = constant

Avogadro’s law

Under the same conditions of temperature and pressure, equal volumes of all ideal gases constain the same number of molecules. this is equivalent to the statement that at a given temperature and pressure one molecular weight of any ideal gas occupies the same volume as one molecular weight of any other ideal gas. There are 2.73 x 1026 molecules per pound mole of ideal gas.

Kinetic theory of gases

The molecules of any substance are in a constant state of motion at all temperatures above absolute zero. The molecules of an ideal gas, however, are completely separated from each other and move with an average velocity, v. molecular velocity increases as the temperature of the gas increases.

Dalton’s law of partial pressures.

The total pressure exerted by a mixture of gases is equal to the sum of the pressures exerted by its components. The pressure exerted by each of component gases is known as its partial pressure.

Amagat’s law of partial volumes.

The total volume occupied by a gas mixture is equal to the sum of the volumes that the pure components would occupy at the same pressure and temperature. The volumes occupied by the individual components are known as partial volume.

Apparent molecular weight of a gas mixture.

a gas mixture behaves as if has a definite molecular weight

Specific gravity. It is defined as the ratio of the density to the density of dry air with both measured at the same temperature and pressure.

Compressibility equation of state. one way of writing an equation of state for a real gas is to insert a correction factor into the ideal gas equation. ”z”¸is known as the compressibility factor, it is the ratio os the volume actually occupied by a gas at given pressure and temperature to the volume gas would occupy at the same pressure and temperature if it behaved like an ideal gas.

Law of corresponding states. All pure gases have the same z-factor at the same values of reduced pressure and reduced temperature.

Van der Waals’ equation of state (1873): this equation differs from the ideal gas equation by addition of the term a/VM

2 that represents an attempt to correct pressure for the forces of attraction between the molecules. The constant b is regarded as the correction to the molar volume due to the volume occupied by the molecules. it often is called two-constant equations of state, although there are actually three constants: a, b and R. these equations also are caleed cubir equations of state.

The five reservoirs fluid.

Black oil: GOR: 2000 scf/STB or less. Stock-tank oil: below 45 OAPI. The stock-tank oil is very dark, indicating the presence of heavy hydrocarbons, often black, sometime with a greenish cast, or brown. This type of reservoir fluid has also been called low-shrinkage crude oil or ordinary oil. Initial oil formation factor of 2.0 res bbl/STB or less.

Volatile oils. Also called high-shrinkage clude oils or near-critical oils. GOR: 2000-3000 scf/STB. Stock-tank oil gravity: 40 OAPI. Bo: greater than 2.0 res bbl/STB. The oil is colored (usually brown, orange, or sometimes green)

Retrograde Gas: GOR: 3000 scf/STB. Stock tank liquid graviry: 40-60 OAPI. the liquid can be lightly colored, brown, orange, greenish, or water-white. Retrograde gases are also called retrograde gas-condensates, retrograde condensate gases, gas condensates, or condensates.

Wet gases. Refers to the hydrocarbon liquid which condensates at surface. Reservoir gas is normally saturated with water. Produce stock-tank liquids with the same range of gravities as the liquids from retrograde gases. A wet gas exists solely as a gas in the reservoir throughout the reduction in reservoir pressure.

Dry gas. is primarily methane with some intermediates. The word dry indicates that tha gas does not contain enough of the heavier molecules to form hydrocarbon liquid at the surface.

Gas formation volume factor is defined as the volumen of gas at reservoir conditions required to produce one standard cubic feet per standard cubic foot. The reciprocal of the formation volume factor sometimes is called gas expansion factor.

Coefficient of isothermal compressibility is defined as the fractional change of volume as

pressure is changed at constant temperature.

Heating value. It is the quantity of heat produced when the gas is burned completely to carbon dioxide and water. It usually value usually is expressed as british thermal units per standard cubic foot of gas, BTU/scf. Wet means that the gas is saturated with water vapor, about 1.75 volume percent. And dry means that the gas contains no water vapor. Gross heating value is the heat produced in complete combustion under constant pressure with the combustion products cooled to standard conditions and the water in the combustion products condensed to the liquid state. Net is defined similarly, except the water of combustion remains vapor at standard conditions.

Formation volume factor of oil. It is defined as the volume of reservoir oil required to produce one barrel of oil in the stock tank. The of Bo is called the shrinkage factor.

Solution gas-oil ratio. The quantity of gas dissolved in an oil at reservoir conditions. It is the amount of gas that evolves from the oil as the oil is transported from the reservoir to surface condition.

Coefficient of isothermal compressibility of oil. at pressure above the bubble point, it is defined exactly as the coefficient of isothermal compressibility of a gas. at pressure below the bubble point an additional term must be added to the definition to account for the volume of gas which evolves.

Coefficient of viscosity of oil. an decrease of pressure causes a decrease in viscosity. A decrease in the amount of gas in solution in the liquid causes an increase in viscosity.

Interfacial tension. The force required to prevent destruction of the surface. The units are in terms of the force holding the surface together in dynes acting along one centimeter of length.