Chapter 3 Flashcards
Important physical properties of crude oil
Fluid Gravity
oil density
crude oil viscosity
specific gravity of the solution gas
gas solubility
Bubble-point pressure
oil formation volume factor
total formation volume factor
Define Crude oil gravity/density
the mass of a unit volume of
the crude at a specified pressure and temperature.
Equation for the specific gravity of a crude oil
the ratio of the
density of the oil to density of water
Yo = Po / Pw
What do the values of Yo = Po / Pw mean?
This is the equation for specific gravity of a crude oil.
Yo - specific gravity of the oil
Po - density of the crude oil, lb/ft^3
Pw = density of the water, lb/ft^3
What does this formula measure?
°API = (141.5 / Yo) - 131.5
The crude oil gravity in API gravity
The API gravities of crude oil usually ranges from 47° API for the ________ crude oils to 10° API for the _________ crude oils.
lighter
heavier
Define bubble point pressure
the highest pressure at which the first bubble of gas is
liberated from the oil
What is the difference between a unsaturated and saturated oil reservoir
Undersaturated is when Preservoir > Pb
When all gases are dissolved in the oil at the reservoir condition
Saturated is when Preservoir <= Pb
When gases are evolved and formed a gas-cap above the oil
Define gas solubility
the number of standard cubic
feet of gas which will dissolve in
one stock-tank barrel of crude oil
at specific pressure and
temperature.
The gas solubility is a function of the ….
pressure, temperature, API
gravity, and gas gravity.
Define oil formation volume factor
Oil formation volume factor describes that if
you produce one barrel of oil from a specific reservoir, how
much the final and gas free volume of oil you have after you
released all gases at the surface.
What is the following formula used for?
Bo = (Vo)p,t / (Vo)sc
and what do the variables mean?
Oil formation volume factor
Bo - oil formation volume factor, bbl/STB
(Vo)p,t - volume of oil under reservoir pressure p and temperature t, bbl
(Vo)sc - volume of oil measured under standard conditions, STB
What does STB stand for and what does it represent?
Stock Tank Barrel
refers to the volume of oil stored at stock tanks at the surface conditions.
Define Isothermal compressibility coefficient of crude oil
co
is
defined for pressures above the bubble-point
Isothermal compressibility coefficient of crude oil uses these varaibles, what do the represent?
Co, Po, Bo
Co - isothermal compressibility, psi^-1
Po - oil density, lb/ft^3
Bo - oil formation volume factor, bbl/STB
Oil formation volume factor for undersaturated oil:
With __________ pressures above the bubble-point pressure, the oil formation volume factor decreases due to the ____________ of the oil
increasing
compression
These variables are used in the oil formation volume factor for undersatured oils. Wat do they represent?
Bo, Bob, Co, P, Pb
Bo = Bob exp (-Co(P - Po))
Bo - oil formation volume factor at the pressure of interest, bbl/STB
Bob - oil formation volume factor at the bubble-point pressure, bbl/STB
P - pressure of interest, psia
Pb - bubble point pressure, psia
Crude oil density is defined as
the mass of a unit volume of crude at a specific
pressure and temperature.
Crude oil density has two equations to use. Why would I use one or the other?
One equation is above bubble point pressure and one is below or equal to bubble point pressure.
These are the two equations for crude oil density. When do I use each one.
Po = (62.4Yo + 0.0136RsYg) / Bo
Po = Pob exp(Co(P - Pb))
Below or equal to bubble point pressure
Po = (62.4Yo + 0.0136RsYg) / Bo
Above bubble point pressure
Po = Pob exp(Co(P - Pb))
Define viscosity
Viscosity is the internal resistance of the fluid to flow. This is an important
parameter which affects the flow of oil in the porous media and pipes.
Viscosity of crude oil can be classified into 3 categories, what are they?
Dead-oil viscosity
saturated-oil viscosity
Undersaturated-oil viscosity
Define dead -oil viscosity
The dead-oil viscosity is defined as the viscosity of
crude oil at atmospheric pressure (no gas in solution) and system
temperature.
Define Saturated-oil viscosity
The saturated (bubble-point)-oil viscosity is
defined as the viscosity of the crude oil at the bubble-point pressure and
reservoir temperature.
Define undersaturated-oil viscosity
The undersaturated-oil viscosity is
defined as the viscosity of the crude oil at a pressure above the bubble-point and reservoir temperature
Important physical properties of natural gas
Apparent molecular weight, Ma
✓ Specific gravity, γg
✓ Compressibility factor, z
✓ Density, ρg
✓ Specific volume, v
✓ Isothermal gas compressibility coefficient, cg
✓ Gas formation volume factor, Bg
✓ Viscosity, µg
Define apparent molecular weight formula
Ma = Σi=1(YiMi)
Ma - apparent molecular weight of a gas mixture
Mi - molecular weight of the ith component in the mixture
Yi - mole fraction of component i in the mixture
Define standard volume
The standard volume is defined as the volume of gas
occupied by 1 lb-mol of gas at standard conditions.
Vsc = 379.4 scf/lb-mol
Equation for gas density is
Pg = pMa / RT
Pg - density of the gas mixture, lb/ft^3
Ma - apparent molecular weight
Define gas specific gravity/ how to calculate it
The specific gravity of a natural gas is defined as the ratio of the
density of the gas to density of air
Yg = Pg/Pair
Yg = Ma/Mair = Ma/28.96
What do the variables in this formula mean?
Yg = Pg/Pair
Yg - gas specific gravity
Pair - density of the air
Pg - density of the gas
What is the gas formation volume factor
The gas formation volume factor, Bg
, is defined as the ratio of
the volume of gas at the reservoir temperature and pressure to
the volume of oil at standard conditions
What is this formula used for? define each variable
Bg = Vp,t / Vsc
Bg - gas formation volume factor, ft^3/scf
Vp,t - volume of gas at pressure p and temperature, t, ft^3
Vsc - volume of gas at standard conditions, scf
Standard condition for pressure and temperature
14.7 psia
60° F
