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• where natural gas can be injected and stored relatively easily, and can be fully withdrawn from the storage layer cost-effectively.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 of 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 cubic metres, 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 Zsanai 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 expansion completed by autumn 2009, the storage capacity increased by 600 million cubic metres, reaching nearly 2.2 billion cubic metres, while the daily withdrawal capacity rose to 28 million cubic metres per day. Injection capacity has also increased significantly with the new turbo compressors, reaching a rate of 20.4 million m³/day.

Hajdúszoboszló

Withdrawal capacity: 18 Mm³/day

Injection capacity: 12.3 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 cubic metres of natural gas were extracted annually from the Hajdúszoboszló field.

Construction of the facility began in 1977; by 1981, the storage site's 35 wells, each equipped with a special sand screen, were capable of receiving 400 million cubic metres of working gas.

Through further developments, the storage site's working gas capacity reached 1,640 million cubic metres. Reconstruction work began in the 1990s to secure the storage site's existing capacities for the long term.

The storage site, with a current nominal working gas capacity of 1,640 million cubic metres, has a daily withdrawal capacity of 18 million m³ and a daily injection capacity of 12.3 million m³.

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 cubic metres. In 1988, this capacity was expanded by 100 million cubic metres, and additional wells were installed during further developments in 1991.

The current nominal working gas capacity is 340 million cubic metres. The daily withdrawal capacity is 2.88 million m³, while the daily injection capacity is 2.9 million m³. A cushion gas volume of 266 million m³ ensures the smooth operation of the storage facility. A project to extend the service life of the storage facility was recently completed, designed to ensure its continued smooth operation in the future.

The Pusztederics facility is the only natural gas storage facility in Transdanubia, thus playing an essential role in maintaining the hydraulic balance of the high-pressure pipeline network in the western part of the country.

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 cubic metres of extractable natural gas was discovered in the vicinity of Kardoskút and Pusztaszőlős. Production began in 1966. 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 and storage capacity were expanded, which involved the drilling of numerous new wells.

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 current working gas capacity is 280 million cubic metres, and its withdrawal capacity is 2.9 million cubic metres per day.