Chapter 3 Flashcards by Emma Schmidt

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

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Define Crude oil gravity/density

the mass of a unit volume of
the crude at a specified pressure and temperature.

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Equation for the specific gravity of a crude oil

the ratio of the
density of the oil to density of water
Yo = Po / Pw

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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

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What does this formula measure?
°API = (141.5 / Yo) - 131.5

The crude oil gravity in API gravity

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The API gravities of crude oil usually ranges from 47° API for the ________ crude oils to 10° API for the _________ crude oils.

lighter
heavier

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Define bubble point pressure

the highest pressure at which the first bubble of gas is
liberated from the oil

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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

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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.

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The gas solubility is a function of the ….

pressure, temperature, API
gravity, and gas gravity.

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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.

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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

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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.

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Define Isothermal compressibility coefficient of crude oil

co
is
defined for pressures above the bubble-point

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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

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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