In Hungary, gas storage facilities are porous geological structures. In most cases, the rock is sandstone (Hajdúszoboszló, Pusztaederics, Kardoskút), with one exception (Zsana), where it is limestone.  These geological formations – where natural gas production has been partially or fully completed, and which have been reliably proven to be suitable for natural gas storage – have been converted into underground gas storage facilities. The conversion involved:

• the conversion of wells originally used for gas production and, where necessary, the drilling of new ones;
• the construction of a natural gas gathering and distribution system;
• the installation of related injection and gas processing equipment;
• and the construction of relevant transmission pipeline connections.

The first facility in Hungary for underground gas storage was built near Őrszentmiklós to store natural gas produced in this region. From 1960, natural gas stored here also helped meet the peak demand of Budapest during the winter period. However, the continuous increase in the demand for natural gas made it necessary to establish additional underground storage facilities. The programme started in 1978 with the conversion of the depleted working natural gas field in the area of Kardoskút, and was continued the following year by commissioning two additional facilities in Hajdúszoboszló and Pusztaederics. Currently, we operate four underground gas storage facilities: Pusztaederics, Kardoskút, Hajdúszoboszló and Zsana.

Capacities

Hungarian Gas Storage Ltd. operates four underground gas storage facilities in Hungary, with a total storage capacity of 4.43 billion m³ of working gas plus 420 Mm³ of additional capacity.

Storage cycles:

Start of injection period: 1 April

End of injection period: 30 September

Start of withdrawal period: 1 October

End of withdrawal period: 31 March

Natural Gas Storage Sites

Hungarian Natural Gas Storage Ltd. has four underground gas storage sites, where it stores natural gas in partially depleted natural gas fields (in gas-bearing geological formations and gas reservoirs).

Only those gas-bearing reservoirs can be considered for natural gas storage

• whose impermeability has been proven for subsequent storage operations,
• where the storage rock itself has the necessary storage properties and is also sufficiently stable,
• where natural gas can be injected and stored relatively easily, and can be fully withdrawn from the storage layer cost-effectively.

Only a fraction of the hundreds of depleted fields meet these requirements. Naturally, in addition to technical considerations, economic calculations also play a role in selecting a storage site. A fundamental requirement, for example, is that natural gas must be injectable at a relatively low pressure of 60–80 bar, with a maximum of 210 bar. This is possible if the reservoir is located at a depth not exceeding 2000–2500 metres, and its reservoir rock has high permeability.

Zsana

 Withdrawal capacity: 28 Mm³/day

Injection capacity: 20.4 Mm³/day

Working gas capacity: 2,170 Mm³  + 230 Mm³

Exploration for hydrocarbons began in the vicinity of the village of Zsana in 1978.

Over the ten-year period between 1982 and 1992, approximately 4 billion  m³ gas was produced from the gas reservoirs in Zsana, and then the construction of the Zsana gas storage site began in 1992.

The storage facility’s initial capacity was 600 million m³, and the first withdrawal took place in November 1996. At that time, the facility’s daily withdrawal capacity was around 8 million cubic metres. Owing to its geological characteristics (limestone reservoir) the Zsana storage site is the most flexible natural gas storage facility in Hungary. Four layers at depths of 1,695–1,780 metres below sea level take part in natural gas storage.

Following a multi-phase expansion, the storage facility’s capacity grew to 1,570 million m³ by 2008, with a peak withdrawal capacity of 24 million m³/day and a peak injection capacity of 10.2 million m³/day.

In the summer of 2008, a further expansion of the storage facility began with an investment of HUF 32 billion. Due to the development completed by autumn 2009, the storage site's capacity expanded by 600 million m³, reaching nearly 2.2 billion m³, while the daily withdrawal capacity rose to 28 million m³.  Injection capacity has also increased significantly with the new turbo compressors.

The technological upgrade of the storage site was continued in the following years. Between 2017 and 2018, as part of low-temperature separation technology improvements, three Cold Box plate heat exchangers were replaced and three screen separators were installed. In 2019, as part of further technological development, an expansion control valve was installed in the inlet line of the three Cold Box plate heat exchangers, which further enhanced the system’s efficiency.

In 2025, another substantial investment was completed via the installation of a gas-engine-driven reciprocating compressor, resulting in the storage site's injection capacity reaching 20.4 million m³/day. These improvements served to further strengthen the storage site's operational efficiency, flexibility and role in ensuring security of supply.

Hajdúszoboszló

Withdrawal capacity: 18 Mm³/day

Injection capacity: 12.8 Mm³/day

Working gas capacity: 1,640  Mm³  + 150  Mm³

Hajdúszoboszló was once Hungary's most important natural gas field. The exploitation of the deposits discovered during the 1950s marked the beginning of the natural gas era in Hungary. During the boom period of natural gas production, starting in the late 1960s, 1.8 billion m³ of natural gas were extracted annually from the Hajdúszoboszló field.

Construction of the facility began in 1977; and by 1981, the storage site's 35 wells, each equipped with a special sand screen, were capable of receiving 400 million m³ of working gas. The first major development milestone was reached in 1985, when the capacity of the Hajdúszoboszló storage site was expanded.

From the 1990s, continuous maintenance and reconstruction work began in order to ensure that the storage site’s existing capacities could be sustained over the long term. As part of this, 425 million m³ of cushion gas was replenished. As a result of further improvements, the storage site’s working gas capacity reached 1,640 million m³.

In 2008, the storage site’s technological system was further modernized through the installation of three Siemens turbo compressors. The development process continued in 2015 with the transfer of the gas cooler to the withdrawal technology, followed in 2021 by the replacement of the north–south pipeline of DN 500 diameter.

As a result of the developments carried out in 2025, the storage site's rated working gas capacity remained unchanged at 1,640 million m³, while the daily withdrawal capacity reached 18 million m³/day, and the injection capacity rose to 12.8 million m³/day, thereby further enhancing the site's operational safety and efficiency.

Pusztaederics

Withdrawal capacity: 2.88 Mm³/day

Injection capacity: 2.9 Mm³/day

Working gas capacity: 340 Mm³

The Pusztaederics gas storage site is operated in sandstone formed in the Lower Pannonian period (upper and lower Nova reservoirs, Szolnok Sandstone Formation).

The storage site was created by repurposing the depleted Hahót-Ederics natural gas field. The idea of establishing the storage site first emerged in the 1970s.

Between 1972 and 1979, five former natural gas production wells were put into use for gas storage, making the Pusztaederics facility Hungary’s first natural gas storage site. By 1979, an additional seven wells had been completed, at which point the facility was officially qualified as a natural gas storage site. At that time, there were a total of 12 wells with a working gas capacity of 100 million m³. In 1988, the storage facility’s working gas capacity was expanded by 100 million m³, and additional wells were constructed in 1991 as part of further developments.  The current nominal working gas capacity is 340 million m³, and the cushion gas volume ensuring the smooth operation of the storage facility is 266 million m³.

Developments serving the long-term, safe operation of the storage site continued in subsequent years. In 2011, a project was implemented to extend the service life of the Pusztaederics natural gas storage site. Subsequently, in 2016, the compressor’s operating gas cooling system was converted to air-cooling technology, and in 2018, the withdrawal system was modernized by replacing the gas-to-gas heat exchangers. In 2021, quick action blind isolation valves were installed to ensure even safer and more efficient operation. The upgrades continued in 2025 with the reconstruction of the electric drives for the K-001 and K-002 compressor units.

Kardoskút

Withdrawal capacity: 2.9 Mm³/day

Injection capacity: 2.64 Mm³/day

Working gas capacity: 280  Mm³  + 40  Mm³

In 1960, a field containing slightly more than 1 billion m³ of extractable natural gas was discovered in the vicinity of Kardoskút and Pusztaszőlős. Production began in 1966. Once the field was depleted, its use for natural gas storage began in 1978, starting with only seven wells. Between 1980 and 1984, surface facilities were upgraded and storage capacities were expanded through the drilling of numerous new wells. The next major development phase began in 1993 with the launch of the four-year Phase II expansion, which further increased the storage capacity and operational safety of the facility.

In 2001, comprehensive renovation work was carried out, which included replenishing the cushion gas and the construction of additional wells.  Technological modernization continued in 2018 via the installation of an LTS gas processing unit, followed in 2021 by the replacement of the 10GKN compressor units with state-of-the-art, electrically driven reciprocating compressors, further improving the storage site's energy efficiency and operational safety.

In 2026, the facility reached another milestone: a resolution on the modification of the mining plot allowed for the storage of hydrogen, supporting the energy transition and the adoption of innovative energy storage solutions.

The average depth of the sandstone reservoir suitable for natural gas storage is 1,000–1,100 m. The Kardoskút storage site currently operates with 21 production wells and 8 observation wells. Its nominal working gas capacity is 280 m³, and its daily withdrawal capacity is 2.9 million m³.