The Natural Gas System includes the following activities: Reception, Storage and Re-gasification of liquefied natural gas (LNG); Underground storage of natural gas; Transmission of natural gas; Distribution of natural gas; Supply of natural gas; Operation of natural gas markets and logistic operation for the switching of natural gas supplier, as stated in Decree-Law no. 30/2006 of the 15th of February:
- Acquisition/Import: Natural gas is extracted from underground deposits and reaches Portugal mainland through gas pipelines (in gaseous state) or aboard LNG carriers that unload at the Sines Terminal (in liquid state – LNG). Currently, the country's main natural gas suppliers are Algeria and Nigeria.
- Reception, Storage and Re-gasification: these activities take place at the Sines terminal, the only one in the country, which began operations in 2004. After the liquid natural gas is unloaded from the LNG carriers, it is stored in tanks and later re-gasified according to the country's consumption needs. There is also a quantity of natural gas which is not re-gasified and which is transported by tankers to autonomous gas units.
- Underground Storage: this activity is strongly related to the need to constitute and maintain the country's safety reserves, essential to promote conditions to guarantee the supply of natural gas to the country. In addition to the safety reserve, there is also an operational reserve which allows the management of a stock of natural gas to guarantee the availability of this product if there is a need for additional supply. There is one underground storage complex in Portugal mainland located in Carriço.
- Transmission: allows the transport of natural gas in gaseous state, through High Pressure networks (higher to 20 bar) for reception and delivery to distributors, suppliers or large customers The transmission activity also includes the transport of liquefied natural gas in tankers to the autonomous gas units and respective delivery to distributors or large customers.
- Distribution: allows the distribution of natural gas in gaseous state, through Medium and Low Pressure networks (less than 20 bar) for reception and delivery to end users. The distribution activity also includes the reception, storage and re-gasification of natural gas in autonomous gas units and its delivery to supply points through the respective distribution networks.
- Supply: gas suppliers are responsible for managing the relations with the end, customers including billing and energy-related, advice and support. In Portugal,mainland the supply of natural gas can be done on the liberalized market, with free suppliers, and on the regulated market, with last resort suppliers. Tariffs per activity.