FROM THE DEPTHS OF THE
N
atural gas, sometimes also referred to as the “blue fuel”, is a type of natural
resource which is created as a result of anaerobic decay of organic substances
found deep underground. Its chemical composition may vary, mainly depending on the
location of the field. There are different types of gas: ‘wet’ gas (which contains higher
hydrocarbons), ‘dry’ gas (mostly consisting of methane) and ‘sour’ gas (contaminated
with sulfur), but the main component of any type of natural gas is always methane.
Natural gas occurs in different locations. Gas contained in rocks with good porosity
and permeability parameters (e.g. sandstone) is called ‘conventional gas’, whereas
gas produced from low-porosity and low-permeability rocks (e.g. shale rock) is
called ‘unconventional gas’. One should bear in mind that what is known as ‘shale
gas’ is really, as far as its composition and properties are concerned, no different
from ordinary natural gas, which is well-known and used on an everyday basis. The
difference only lies in different properties of the clay and silt-based rocks in which
it occurs, and consequently - different methods of producing it. Regardless of its
origin, the gas brought to the surface through the borehole has to be subjected to
the same, quite complicated technological treatment.
W
hen the decision to commence industrial-scale gas production is made, the field development stage begins. During this
stage, the infrastructure that will make it possible to produce gas and deliver it to the market is developed. This may take
several years and it includes: building gas plants, network of gathering pipelines and connecting to networks of transmission
and distribution pipelines, and setting up other devices necessary to ensure industrial-scale production of gas. When the
infrastructure is ready, the production stage begins. Producing gas has a negligible impact on the surroundings and the
landscape. Only the head of the well (known as the ‘Wellhead/Christmas tree’), which seals and secures the borehole, and
a small amount of accompanying infrastructure, marks the presence of the well. No more than a dozen or so square metres
are taken up, instead of several hectares needed for the drill rig.
A
fter extraction to the surface, natural gas is colourless, lighter than air, and quite
significantly contaminated (by other gases, sand, liquid hydrocarbons, water
etc.). Before it is sent on through the pipeline, it must be subjected to complicated
technological treatment, as a result of which its composition changes and it becomes
suitable for transport and use. The purification of natural gas is a multi-stage process.
First, it undergoes preliminary on-site purification at the well, and then it is sent from
the wellhead, through the process pipelines, to a processing plant.
Industrial chemical processes are used at the processing plant to remove solid
particles, water vapour, sulfur, and other impurities. Key industrial chemical
processes used at a processing plant include:
n
Dehydration, or the separation of gas from water and other impurities contained in water. Wastewater is stored at wastewater
tanks, and then treated.
n
Purification of gas, which involves drying, CO
2
removal, and the removal of natural gasoline (separation of heavier hydrocarbons).
Propane and butane, after their separation from natural gas, are usually converted into liquid petroleum gas (LPG), which is used in
cookers, gas-fired grills, and widely used as car fuel.
n
Sulfur removal (a.k.a. ‘sweetening’) is used when the hydrogen sulphide is detected, as it is poisonous and induces corrosion.
The quality of natural gas delivered to customers is defined by the Regulation of the Minister of Economy on the detailed operating
conditions of the gas network of 2 July 2010, by the Polish Standard PN-C-4750-53 and appropriate network operator code.
2
natural gas is odourless?
Natural gas does not have a smell. Its characteristic odour is obtained through artificial odourization. It is a necessary
precaution because the mixture of natural gas and air at certain concentrations (5-15%, usually in closed spaces) is
explosive. The most common odourization agent used for natural gas is THT, or tetrahydrothiophene.
Different sources - same gas
Field development
Processing natural gas
DID YOU KNOW THAT:
