Storage consists of holding gas in underground caverns, at high pressure, to manage the commercial flows of natural gas, but also to build up strategic stocks and for operational purposes.

Portugal has gas storage facilities at Carriço (near Figueira da Foz), in natural salt cavities located at great depth, interconnected with a gas station that manages the injection, from the transmission network, using compressors, or extraction with gas dehydration systems for subsequent injection into the transmission network, under the appropriate technical conditions.

REN Armazenagem, S.A. is the operator of the underground storage (operador de armazenamento subterrâneo - OAS), under concession. The OAS allocates capacity in its infrastructure, to users, through an electronic platform.

The ten-year investment plans for underground storage infrastructures are part of the investment plan for the transmission network and high-pressure infrastructures (PDIRTG).

ERSE is responsible for the economic regulation of the gas underground storage activity, setting the tariffs for the use of the infrastructure and the operator’s revenues.

The rules governing the use of underground storage are set out in the Regulation on Access to Networks, Infrastructures and Interconnections and respective supplementary rules, all approved by ERSE.

To find out more about this, have a look at the pedagogical guide Natural gas: how does it work?

The certification of the operator of the National Storage Network is an obligation that stems from Article 3.º of Regulation (EC) 715/2009, as amended by Regulation (EU) 2022/1032, considering Decree-Law n.º 62/2020, of 28 August, in its current wording.

ERSE, as the certification body, in light of the legal requirements, has to analyse the risk to the security of energy supply or the essential security interests of the Union or any Member State.

Under the procedurally applicable terms, ERSE submitted its draft decision to the European Commission in November 2023, which issued its opinion in July 2024. In the same month, ERSE issued the final decision on the Certification of REN - Armazenagem, S.A