Base Gas, also known as Cushion Gas, refers to the volume of natural gas that must remain in an underground storage reservoir to maintain sufficient pressure for the efficient withdrawal of the working gas. This term is crucial in the natural gas industry, particularly in the context of underground storage facilities.
Definition
Base Gas (Cushion Gas) is the volume of natural gas required to maintain the reservoir pressure necessary for the extraction of working gas. The pressure created by the base gas ensures that the working gas, which is the gas available for withdrawal to meet customer demand, can be efficiently and reliably accessed.
Importance in Natural Gas Storage
Reservoir Pressure Maintenance
Base gas is essential for maintaining the pressure in the storage reservoir. Adequate pressure is crucial because it allows for the efficient withdrawal of working gas. Without the necessary base gas, the reservoir pressure would drop, making it more difficult and more expensive to extract the remaining natural gas.
Types of Gas in Storage
- Base Gas (Cushion Gas): This is the gas that remains in the reservoir to maintain adequate pressure.
- Working Gas: This is the gas that can be cycled in and out of the storage facility to meet demand.
Special Considerations
- Permeability and Porosity: The amount of base gas required can vary depending on the permeability and porosity of the storage reservoir. Higher permeability and porosity usually mean a lower requirement for base gas.
- Economic Factors: The cost of maintaining base gas is a significant factor in the economics of natural gas storage. Base gas effectively represents a capital investment because it must remain in the reservoir for the life of the storage facility.
Examples and Applicability
Example of Usage
In a storage facility with a total volume capacity of 100 million cubic meters, it might be required that 30 million cubic meters be designated as base gas. The remaining 70 million cubic meters would then be available as working gas.
Applicability in Industry
Base gas is a fundamental consideration in the design and operation of all types of underground natural gas storage facilities including depleted gas reservoirs, aquifers, and salt caverns.
Historical Context
The concept of base gas became more standardized with the development of natural gas storage technology in the mid-20th century. As natural gas became a vital energy source, reliable storage methods, including the use of underground reservoirs, became essential.
Related Terms
- Working Gas (Injectable/Extractable Gas): The portion of gas that can be cycled in and out of the storage facility to meet market demands.
- Porosity: A measure of how much of a rock is open space, which can affect gas storage capacity.
- Permeability: The ability of a rock to transmit fluids, essential in evaluating how easily gas can be extracted from a reservoir.
FAQs
How is the required volume of base gas determined?
Can the volume of base gas change?
What happens if the base gas is withdrawn?
References
- Natural Gas Storage Principles: Society of Petroleum Engineers. Journal of Petroleum Technology.
- Energy Information Administration - Underground Natural Gas Storage: Retrieved from EIA.gov
- Fundamentals of Natural Gas Processing by Arthur J. Kidnay and William R. Parrish
Summary
Base Gas (Cushion Gas) is a critical component in the operation of natural gas storage facilities, ensuring that adequate reservoir pressure is maintained to allow efficient gas withdrawal. It encompasses a fundamental aspect of reservoir engineering and the economics of natural gas storage, playing a vital role in meeting energy demands. Understanding the intricacies of base gas helps in optimizing storage operations and ensuring reliable gas supply.
