After gas has been extracted from the land or sea subsurface, it needs to be delivered to consumers. The length of gas pipelines and gas distribution networks multiply exceeds the circumference of the Earth.
Gas is pumped at long distances using trunk gas pipelines, but for delivery of gas to end consumers, gas pipelines of a smaller diameter – gas distribution networks – are used. Depending on the consumer category, there are low-pressure (for gas supply to residential buildings), high-pressure, and medium-pressure networks designed for supplying industrial plants.
The most common method of gas delivery to consumers is the transmission via pipelines.
But before gas is pumped into pipelines, it must be treated. The matter is that different admixtures that can damage the equipment come out of the well together with natural gas. Gas is cleaned from them several times: right at the well outlet, in surface separators, and in addition during the transmission and at compressor stations.
Transmission process requires careful attention of an entire team of dispatchers who record pumping conditions. They take note of daily and seasonal fluctuations in gas consumption at the terminal point.
Excess substances in gas
Gas needs to be dried, since moisture contained in it can damage equipment and form plugs in the pipe, the so-called crystalline hydrates, which are similar to wet compacted snow. Gas is dried by running it through adsorbents or by cooling the gas stream. Gas can be cooled using cooling plants or by throttling – pressure reduction in a narrow part of a pipeline. Furthermore, hydrogen sulfide and carbon dioxide must be removed from gas before it is pumped into the pipe.
Since natural gas has no odor, it is odorized before delivery to consumers.
Gas is less needed in summer
While daily fluctuations in gas consumption are controlled by dispatchers, seasonal fluctuations are compensated by changing operating conditions of the compressor station (CS), where gas is compressed, or by connection to the pipeline of a gas storage facility (UGS).
In the process of gas compression, its temperature is increased at CS, so that gas should be cooled in order to prevent damage to the equipment. To do so, air coolers (AC) are used. Besides, gas is cooled to increase the gas pipeline throughput capacity.
Natural gas occupies the smallest volume when it is in liquefied form. It can be transported as well, but in special tanks.
Gas in numbers
The maximum diameter of the gas pipeline in terms of efficiency is considered to be 1,420 millimeters.
Russian gas transmission system is the largest in the world. In 2010, average distance of gas transmission was over 2,500 kilometers for domestic supplies and almost 3,300 kilometers for export supplies.
To date, length of trunk gas pipelines in Russia accounts for 161,700 kilometers. That’s enough pipelines to circle the Earth four times.
The length of gas distribution pipelines operated by subsidiaries and affiliated companies of Gazprom is over 632,000 kilometers, i.e. 80 per cent of the total length of gas distribution networks in Russia. The length of all gas distribution networks in Russia totals about 765,000 kilometers, which is already almost 20 times greater than the Earth’s circumference.