Oil and gas production handbook An introduction to oil ... - ABB Group

Gas treatment may also include calibration. If the delivery specification is for
a specific calorific value (BTU per scf or MJ per scm), gas with higher values
can be adjusted by adding an inert gas, such as nitrogen. This is often done
at a common point such as a pipeline gathering system or a pipeline onshore
terminal.
Raw natural gas from the well consists of methane as well, as many other
smaller fractions of heavier hydrocarbons and various other components.
Component Chemical
Formula
Boiling Point
at 101 kPa
Vapor pressure
at 20 °C approx.
Methane CH 4 -161,6 °C T cri t −82.6 °C
@ 4,6 MPa
Ethane C 2 H 6 -88.6 °C 4200 kPa
Propane C 3 H 8 -42.1 °C 890 kPa
Butane n-C 4 H 10 −0.5 °C 210 kPa
Higher order HC
Alkenes
Aromatics
Acid gases
Carbon dioxide
Hydrogen sulfide
Mercaptans ex.
Methanethiol
Ethanethiol
Other Gases
Nitrogen
Helium
C n H 2n
e.g. C 6 H 6
CO 2
H 2 S
CH 3 SH
C 2 H 5 SH
N 2
60
−78 °C
-60.2 °C
5.95 °C
35 °C
-195.79 °C
-268.93 °C
5500 kPa
He
Water H2O 0 °C
Trace pollutants
Mercury
Chlorides
Data source: Wikipedia, Air Liquide Gas Encyclopedia
Natural gas is characterized in several ways dependent on the content of
these components:
o Wet gas is raw gas with a methane content of less than 85%.
o
o
Dry gas is raw or treated natural gas that contains less than 15 liters
of condensate per 1,000 SM 3 . (0.1 gallon per 1000 scf).
Sour gas is raw gas with a content of more than 5.7 mg hydrogen
sulfide (H 2 S) per scm (0.25 grains per 100 scf); this is about 4 ppm.