Tvrdonice underground gas storage (UGS) facility, owned by RWE Gas Storage, is located in the Southern Moravia region of the Czech Republic. It is the first and the oldest such facility to be developed in the territory of former Czechoslovakia.
It stores natural gas in original partially exploited natural deposits of gaseous hydrocarbons.
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Tvrdonice is one of the six UGS facilities operated by RWE in the Czech Republic. The other five facilities are located in Dolni Dunajovice, Stramberk, Lobodice, Tranovice and Haje. The combined storage capacity of all the facilities is 2.5 billion cubic metres (bcm).
UGS facilities like Tvrdonice were developed to ensure all-year round gas supply. Surplus gas is stored in the UGS facilities during periods of low demand.
The gas is withdrawn and supplied through the national transmission and distribution system when the demand increases. The storage facility thus balances the seasonal differences between natural gas consumption and supplies.
Site choice for the Tvrdonice underground gas storage
A partially exploited oil and gas field named the Central Moravian Depression was developed into the Tvrdonice UGS. The deposit is part of the Tertiary Vienna basin which was one of the richest oil and gas bearing regions in central Europe. It spans 4.9km² across the Czech Republic, Slovak Republic and Austria. It features normal faulted, structural and lithological traps.
Gas is stored in collector rocks located in three storage sand horizons – eighth Sarmatian, 12th-14th Sarmatian and ninth Upper Badenian. The thickness of the rocks ranges from 7m to 30m.
The Tvrdonice UGS offers higher storage depths and deposit pressures compared to other storage facilities. Majority of the storage capacities are available at depths of 1,050m to 1,600m.
Another key feature of the Tvrdonice UGS is that a number of companies are still producing oil and gas from deposits located near the facility. Construction of the Tvrdonice UGS served as the basis for the development of similar UGS facilities across the country.
Construction of the UGS facility
Construction of the Tvrdonice UGS was started in 1971 and was completed in three phases. Pilot operations started at the facility by 1973 with the commissioning of the first compressor. Gas injection into the facility also commenced during this period. The first phase of construction was accomplished in 1975.
The second phase of construction which started in 1980 was completed in three years. It improved the storage capacity and reliability of the facility. Two satellite collection centres were also added to the facility during this phase.
The final phase of construction commenced in 2004. It involved automation of the facility and installation of a control system to improve the safety and reliability. The existing underground equipment and technology were upgraded during this phase.
RWE increased the storage capacity of the facility by 50 million cubic metres in January 2010.
Infrastructure of the Tvrdonice UGS complex
The facility is equipped with three CKD type 4 JBK 240 compressors to inject gas underground.
The compressors feature electric drives and compressed gas air coolers. Two multicyclones and dust filters are installed to remove impurities from the gas during the injection.
Two orifice metering runs are used to measure the quantity of gas injected. Methanol is automatically injected during gas injection to prevent the formation of hydrates. All underground gas storage control processes are managed by a control system.
The Tvrdonice UGS is connected to the Hrušky-Tvrdonice-Mutenice transport pipeline.
Expansion
RWE Gas Storage is expanding the storage capacity of its Tranovice and Tvrdonice underground gas storage facilities. Expansion of the Tranovice facility was completed in May 2012. The expansion increased the storage capacity of the Tranovice UGS by 290 million cubic meters. The expansion was financed with a European Union grant of €20.4m.
Expansion of the Tvrdonice UGS will increase its capacity by 160mcm. The first phase of expansion was completed by December 2011.
