Definedīelow, it is a function of the fluid composition and the pressure/temperature Is used to convert surface measured volumes to reservoir conditions, assuming the fluid is in a single gas phase despite temperature and pressure changes. Reservoir conditions divided by gas volume at standard conditions. The gas formation volume factor is the gas volume at Where B o is the oil formation volume factor, R s is the solution gas ratio, and R v is the vaporized oil ratio. When the gas is saturated (i.e., pressure is less than the dew point pressure), it is expressed as: Thus, the magnitude of gas compressibility is Where p is the specified pressure, B gd is the dry gas formation volume factor, and Z is the gas compressibilityįactor at that pressure. When the gas is undersaturated (i.e., the pressure is greater than the dew point pressure), mathematically it can be expressed as: Gas compressibility, when plotted versus pressure, shows a Is a very strong function of pressure and increases as the pressure decreases. Not be confused with the gas compressibility factor. Volume per unit change in pressure. The gas compressibility should Gas compressibility is the relative change in The gas compressibility factor directlyĪffects the gas compressibility. It is sometimes called the super-compressibility factor, and is oftenĬonfused with the term ‘compressibility’ (which is the change in volume In the calculation of gas pseudo-pressures, and in converting gas volumesĪnd rates from standard conditions to reservoir conditions (and vice-versa). The gas compressibility factor is usually between 0.8Īnd 1.2, but it can be as low as 0.3 and as high as 2.0. Pressure and temperature if it behaved like an ideal gas. Pressure and temperature to the volume the gas would occupy at the same The gas compressibilityįactor is the ratio of the volume actually occupied by a gas at a given Measure of its deviation from ideal gas behaviour. The gas compressibility factor of a natural gas is a The gas gravity affects the calculations of gas viscosity,Ĭompressibility, compressibility factor, and solution gas-oil-ratio. Petroleum gases typically have a gravity of about 0.65. Ranges from 0.55 for dry sweet gas to approximately 1.5 for wet sour gas. The natural gas divided by the molar mass of air (28.94 kg/kmol). It Gas gravity is the molar mass (molecular weight) of The correction factor is called the gas compressibility factor theĭeviation from ideal gas behaviour. The ideal gas equation, real gas behaviour can be accurately predicted. By inserting a correction factor (Z) into The behaviours of most real gases do not deviate drastically from the behaviour Most real gases at low pressures and it serves as a starting point toĭevelop equations of states for real gases at elevated pressures.

However, this equation does describe the behaviour of This equation has limited practical value since no known gas behavesĪs an ideal gas. The properties of gases differįrom liquids mainly because the molecules in gases are much further apart Which has neither independent shape nor volume. It expands to completelyįill the vessel in which it is contained. A gas can be defined as a homogenous fluid of low density and low viscosity,

Definition of viscosity in oil and gas