Page 314 - Principles of Applied Reservoir Simulation 2E

Part V: Technical Supplements 299

have a relatively small y o and a correspondingly large API gravity. Light oils
typically contain a large amount of gas in solution.

Gas-Liquid Ratio
The gas-liquid ratio is defined as the volume of gas divided by the volume
of liquid, usually oil or water. The gas volume and liquid volume should be
expressed at the same temperature and pressure.

Viscosity
The coefficient of viscosity is a measure of resistance to flow of the fluid.
In general, gases have a lower viscosity than liquids. The inverse of viscosity
is called fluidity [McCain, 1990]. Thus, a fluid with a large viscosity has a low
fluidity.
The relationship between viscosity and shear rate defines the rheology
of the fluid. If fluid viscosity is independent of flow rate, the fluid is referred
to as a Newtonian fluid. If fluid viscosity depends on flow rate, the fluid is
considered a non-Newtonian fluid.
Two types of viscosity may be specified: dynamic viscosity p, and
kinematic viscosity V. They are related by the expression [I = p v where p is the
density of the fluid. Dynamic viscosity |i is used in Darcy's law to calculate the
rate of fluid movement fluid flow in porous media. Typically, the unit of
dynamic viscosity Ji is centipoise. If fluid density p has the unit of g/cc, then
kinematic viscosity v has the unit of centistoke. Thus, 1 centistoke equals 1
centipoise divided by 1 g/cc.
Reservoir fluid properties (PVT data) include fluid viscosities, densities,
formation volume factors, gas solubilities, etc. These data are usually obtained
by laboratory analyses applied to fluid samples taken from the reservoir. They
are sketched in ChapterB.

Differential to Flash Conversion
Laboratory reservoir fluid analyses generally provide data from both a
differential liberation experiment and a flash experiment approximating field
separator conditions. The differential and flash liberation data can be signifi-