EHSQL(Environment-Energy ,Health,Safety, Security and Social Ac. ,Quality-Lab) Technical services: Natural Gas Facts & Figures

Saturday, 1 June 2019

Natural gas is the earth's cleanest burning hydrocarbon.
Its combustion does not produce ash residues, sulphur oxides, and only negligible nitrogen. This sets it apart from all the other fossil fuels.
Natural gas forms organically over millions of years from decomposing plant and animal matter that is buried in sedimentary rock layers. Once formed the gas tends to migrate through the pore spaces, fractures, and fissures in the sediment and rocks.
Some of this gas makes it to the surface naturally showing up in seeps, while the other gas molecules move until they are trapped in impermeable layers of rock, shale, salt, or clay.
These trapped deposits are the reservoirs used to recover natural gas, typically located between 1 and 7.5 kilometers deep.
Natural gas is found throughout the world either by itself or in association with crude oil, both under dry land and beneath the ocean floor.
Methane, or CH4, is the primary component of natural gas.
When it is found in nature, raw natural gas may also contain some mixture of butane, propane, and pentane gasses, as well as some nitrogen, carbon dioxide, and water vapour.
Prior to entering market the raw natural gas undergoes processing, which purifies it into methane with some ethane.

These are the simplest formations, or geological traps, of natural gas, which result from the gas migrating through the pores in permeable rock, until it reaches an impermeable rock cap and becomes trapped.
The lower specific gravity of natural gas, than that of other materials found in the earth, causes it to migrates up, leaving water and other materials at the bottom.
When a well is drilled into such a reservoir, the gas flows upwards through the well, forced by its higher pressure beneath the surface.

Tight Sands Gas is trapped in sandstone and carbonate, which has very low permeability, thus restricting its ability to flow to the surface.
Coalbed Methane is absorbed by the solid coal particles in coal and extracted from coal mines usually by removing water from the reservoir.
Shale Gas is formed in low permeability shale rock and trapped in clay particles or in small pores and micro-fractures in the rock.
Methane Hydrates refers to a form of porous ice that traps methane molecules, the chief constituent of natural gas. Hydrate deposits generally occur deep under Arctic permafrost, and beneath the ocean floor. 1 m3 of gas hydrate releases 164 m3 of natural gas when extracted.

Resources are estimated volumes of natural gas - discovered or undiscovered.
Estimates of discovered resources are quantities of gas in known reservoirs, that may be remote from existing pipelines and markets.
Undiscovered resources are estimates based on geological data of gas volumes thought to be recoverable under current or anticipated techno-economic conditions.

Natural gas reserves have high certainty estimates of volumes that are recoverable, under existing technological and economic conditions.
Reserves are accessible through existing pipelines and markets.

An extensive network of high and low-pressure pipelines enables transportation of natural gas from production to demand points.
There are three major types of pipelines along the transportation route: the gathering system, the transmission pipelines, and the distribution lines.
- The gathering pipeline system includes low pressure, small diameter pipelines that transport raw natural gas from the production site to the processing plant, where it is purified and prepared for the end-use consumption.
- Transmission pipelines are large diameter, high-pressure lines carrying large volumes of natural gas over long distances to consumption, or export hubs.
- Distribution line system is the smaller diameter distance network that delivers natural gas to low final consumers, including homes and business, but excluding large industrial users who are connected directly to the transmission system.

Natural gas can also be shipped over long distances as a liquid, known as liquefied natural gas, or LNG.
In order to transform natural gas into liquid phase, it has to be chilled to -160 degrees C(-256 degrees F) at atmospheric pressure.
This reduces the gas volume by 600 times and makes it possible to transport very large energy content over short and very long distances in specially-designed ocean tankers and trucks.
When the shipment of LNG reaches its destination at the receiving terminal, it is re-heated and converted back to a gas via a process known as regasification. It is then sent through pipelines for delivery to end-users.

The natural gas industry value chain consists of a sophisticated network of supply, transit, storage, and demand components.
Natural gas is not only a key input into primary energy systems, but also a valuable feedstock for industries.
The natural gas value chain is also an evolving organism, as the industry continues to innovate in bringing new possibilities of accessing, delivering, and using its product.
The nascent floating LNG (FLNG) and regasification technologies, for instance, are already starting to change the way this value chain will look in the near future.

Natural gas can be measured in metric or imperial units
- by energy content: Gigajoules (GJ) or Million British Thermal Units (MMBtu)
- or by volume: Cubic Metres (m3) or Cubic Feet (cf)