What is Natural Gas?
Natural gas is a mixture of two of the simplest members of the “hydrocarbon” family. As the name suggests, hydrocarbons are chemical compounds made up of a combination of hydrogen and carbon. Natural gas is predominantly made up of the two lightest hydrocarbons, methane (90%) and ethane (10%).
Natural gas and crude oil are formed from the same processes and are often found together. Collectively they are called “petroleum hydrocarbons”.
Where Does Natural Gas Come From?
Petroleum hydrocarbons (ie natural gas and crude oil) are most commonly formed from the decomposition of organic marine growth. During “anoxic” conditions (lack of oxygen), there can be mass extinctions of marine organisms.
During the earth’s early history there have been prolonged periods of worldwide anoxic conditions. The enormous amounts of marine organisms that perished during these events sank to the ocean floor resulting in thick layers of organic–rich sediments. At the same time the earth was geologically very active and the layers of organic–rich sediments were quickly buried due to the onset of rapid sea floor spreading.
Subsequent further burial (and heating due to the pressure this induced) caused this organic material to decompose anaerobically to form petroleum hydrocarbons. Ancient rivers played an important role in trapping these hydrocarbons in underground pools or reservoirs.
Production of Natural Gas
Once the potential underground petroleum hydrocarbon reservoirs have been located, wells are drilled into each reservoir to determine if it actually holds any petroleum hydrocarbons.
Each well has one or more production (tubing) “strings”. Each production string is “completed” in the appropriate underground petroleum reservoir.
Production piping and field processing equipment is installed with trunklines to the main processing plant.
An outer casing is set in the drill-hole and perforations are “shot” through the casing to allow natural gas to enter. A packer is set to force the gas to flow inside the tubing string. A valve at the surface controls the flow of gas to the processing facilities.