Fundamentals of Petroleum Engineering
By: Bilal Shams Memon
NATURAL GAS COMPOSITION,
CLASSIFICATION & ITS PROPERTIES.
NATURAL GAS

Gaseous form of hydrocarbon; homogeneous
mixture of low density and low viscosity.
NATURAL GAS IS PRODUCED FROM…

Oil wells.

Gas wells.

Condensate wells.
NATURAL GAS CHEMICAL COMPOSITION
NATURAL GAS
CHEMICAL
COMPOSITION
HYDROCARBONS
Paraffins
Cyclo
Paraffins
Aromatics
NON
HYDROCARBONS
(impurities)
CO2
H2S
Complex
compounds
like N2, HE &
H2O vapors
NATURAL GAS ELEMENTAL COMPOSITION
NATURAL GAS CLASSIFICATION
1. Wet Gas – Gas contains certain amount of water vapors or
liquid hydrocarbons (e.g.. gasoline).
2. Dry Gas – Gas free from water vapors or liquid hydrocarbons.
3. Sour Gas – Gas containing excessive H2S.
4. Sweet Gas - Gas containing no H2S.
5. Rich Gas – Gas which contains impurities.
6. Lean Gas – Gas which is free from impurities.
PROPERTIES OF NATURAL GAS

Volume – Three dimensional space covered by gas (m³, cm³).

Density – Mass per unit volume of gas (kg/ m³,g/cm³)

Gas Formation volume factor –
(Gas volume @ res. Cond. / Gas volume @ surface condition)

Gas Expansion Factor – Reciprocal of Gas F.V.F.

Compressibility Factor (z) –
(volume @ actual cond. / volume @ ideal cond.)

Specific Gravity – (Gas density / Air density)

Specific Heat – number of BTU needed to raise the temp. up to 1⁰F of 1 lb. of
material.

Latent heat of vaporization – heat that is necessary to change a liquid into gas.
PROPERTIES OF NATURAL GAS

Critical Temperature (Tc)– Highest temp. @ which fluid can exist as liquid or
vapor, above this temp. fluid is gas and can’t be liquid regardless of amount
of pressure applied (⁰R).

Critical Pressure (Pc)– pressure which is required to liquify or condense a
vapor at it Tc. (Psi).

Pseudo Critical Temperature (Tpc) – total molecular temperature.

Pseudo Critical Pressure (Ppc)– total molecular pressure.

Bubble point pressure (Pb) – pressure @ which first bubble of gas is
liberated @ given temperature.

Dew point pressure (Pd) – pressure @ which first drop of liquid forms or
condensation starts @ given temperature.