Author: haroonkhan

The gas formation volume factor (Bg) relates the volume of gas in the reservoir to the volume on the surface (i.e., at standard conditions psc and Tsc). It is generally expressed in either cubic feet or barrels of reservoir volume per standard cubic foot of gas. Assuming a gas deviation factor of unity for the standard conditions, the reservoir volume…

Everything up to this point applies to a perfect or ideal gas. Actually there are no perfect gases; however, many gases near atmospheric temperature and pressure approach ideal behavior. All molecules of real gases have two tendencies: (1) to fly apart from each other because of their constant kinetic motion and (2) to come together…

Because the density of a substance is defined as mass per unit volume, the density of gas, ρg, at a given temperature and pressure can be derived as follows: where Mw = molecular weight Because it is more convenient to measure the specific gravity of gases than the gas density, specific gravity is more commonly used. Specific gravity is defined as…

Ideal Gas Law Relationships that describe the pressure-volume-temperature (PVT) behavior of gases are called equations of state. The simplest equation of state is called the ideal gas law and is given by where p = absolute pressure V = total volume that the gas occupies n = moles of gas T = absolute temperature R′ = gas constant When R′ = 10.73, p must be…

The ratio of the volume that a fluid occupies to the pore volume is called the saturation of that fluid. The symbol for oil saturation is So, where S refers to saturation and the subscript o refers to oil. Saturation is expressed as either a fraction or a percentage, but it is used as a fraction in equations. The saturations of all…

The isothermal compressibility for a substance is given by the following equation: where c = isothermal compressibility V = volume p = pressure The equation describes the change in volume that a substance undergoes during a change in pressure while the temperature is held constant. The units are in reciprocal pressure units. When the internal fluid pressure within…

The porosity of a porous medium is given the symbol of φ and is defined as the ratio of void space, or pore volume, to the total bulk volume of the rock. This ratio is expressed as either a fraction or a percentage. When using a value of porosity in an equation, it is nearly always expressed…

Properties discussed in this section include porosity, isothermal compressibility, and fluid saturation. Although permeability is a property of a rock matrix, because of its importance in fluid flow calculations, a discussion of permeability is postponed until in which single-phase fluid flow is considered.

As fluid from a reservoir is produced and brought to the surface, the fluid remaining in the reservoir experiences changes in the reservoir conditions. The produced fluid also experiences changes as it is brought to the surface. The reservoir fluid typically sees only a decrease in pressure, while the produced fluid will experience decreases in…