Underground storage facilities are crucial to the security of energy supply, and a key to balancing the supply and demand in natural gas consumption between the summer and winter months, according to Stephen Fry, director of PEB Engineers & Constructors.
Additionally, natural gas in storage also functions as insurance against unforeseen accidents, natural disasters or other incidents that may affect the production or delivery of natural gas.
One such underground storage project at the GHG Empelde Underground Gas Storage facility located near the city of Hannover, Germany, involves storing or buffering gas in four underground salt caverns.
The end goal is to bring total natural gas storage in all these caverns to an equivalent of four months of national consumption to which the GHG facility will contribute, Fry said.
To create a storage facility, salt beds or domes must undergo leaching, where injected water is used to dissolve and extract the salt, leaving a large cavern formation.
Natural gas is transported through nearby transmission lines and injected into the salt cavern, where it is securely stored for future use.
These particular caverns are 500 meters under the earths surface and run 1,500 meters deep and 200 meters in diameter. The natural gas is stored at a pressure of 210 barg.
The installation of heavy-duty gas compressors that pressurize the natural gas before it is fed into the caverns is essential to the projects success.
That is why Stadwerke Hannover AG, EON Ruhrgas AG and Wintershall AG (shareholders in the project) say they chose PEG Rohrleitungssysteme Germany, an affiliate of PEB Engineers & Constructors (the Netherlands), as the turnkey supplier.
PEB is an official Dresser-Rand packager and service center for the complete range of Dresser-Rand gas field compressors, including the HOSS heavy-duty separable reciprocating compressor.
The Dresser-Rand HOSS compressor is especially well-suited for gas storage projects where gas injection and withdrawal operating pressures and gas flow volumes typically require cylinder designs that can best accommodate changes in pressure and flow.
For the Empelde project, the HOSS compressor, and later two smaller units, will replace the three 30-year-old gas engine-driven integral compressors currently installed, Fry said.
PEG/PEB will manage the service and maintenance requirements for the new compressor.
Since the official product launch of the HOSS compressor in 2008, Dresser-Rand has sold more than 150,000 horsepower worth of HOSS compressors for various compression applications ranging from typical natural gas transmission to CO2 enhanced oil recovery (EOR).
One important advantage of this heavy-duty compressor is that it has higher gas/frame loads and offers a wide range of cylinder selections to meet specific applications.
For the Empelde project, we selected the HOSS compressor product with its 87,000 lb (39,462.5 kg) frame rod load rating, specialized storage cylinder designs engineered for transmission and high pressure injection. And it met our specific flow requirements, Fry said.
The HOSS compressor was developed to meet our clients needs for larger, higher horsepower gas field compressors that could still be conventionally packaged, said Gary Tas, Dresser-Rand global sales manager for the Separable Reciprocating Strategic Business Unit. Furthermore, these compressors can be easily transported and installed and, when necessary, can be easily relocated. Its an excellent fit for large compression projects, including gas storage.
In my experience, the HOSS compressor package we supplied to the Empelde facility is the gas storage blueprint for other projects of this type, Fry said. We believe our modular compression system package designed specifically for underground gas storage applications has a strong value proposition for our clients in terms of reduced lead time and lower cost for future projects.