Natural gas is primarily composed of methane (CH4), along with other hydrocarbons such as ethane, propane, and butane. It's typically found in underground reservoirs as a separate phase from crude oil. In most cases, natural gas reservoirs contain little or no crude oil, and vice versa.
There are two primary methods used to recover natural gas from underground reservoirs:
1. Conventional Natural Gas Production:
- Conventional natural gas is extracted from conventional gas reservoirs that contain primarily natural gas.
- These reservoirs have a high gas-to-oil ratio (GOR), meaning they contain a substantial amount of natural gas compared to crude oil.
- The gas is naturally present in a gaseous state at reservoir conditions.
- Conventional natural gas production involves drilling a well into the gas-bearing formation and allowing the natural pressure of the reservoir to push the gas up the wellbore.
- The gas is then separated from any associated liquids, such as condensate, and conditioned for transport to market.
2. Associated Natural Gas Production:
- Associated natural gas is extracted alongside crude oil from oil reservoirs that contain both oil and gas.
- These reservoirs have a lower GOR compared to conventional gas reservoirs.
- In oil reservoirs, natural gas is often dissolved in the crude oil or exists as a gas cap above the oil layer.
- As the crude oil is brought to the surface during oil production, the dissolved gas is released from the oil and separated.
- Associated natural gas can also be produced through dedicated gas wells if present in sufficient quantities.
Overall, natural gas is primarily produced from underground reservoirs either as conventional natural gas or associated gas alongside crude oil. It is processed to remove impurities and liquids before being transported to consumers.
