47th Annual AAPG-SPE Eastern Section Joint Meeting

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Underground Storage of Refrigerated Natural Gas in Granites of the Southeastern U.S.


Conventional underground storage sites for natural gas (salt caverns, depleted gas and oil reservoirs, and aquifers) are either rare or absent along the U.S. eastern seaboard. The potential exists for underground storage of refrigerated natural gas in mined caverns (RMC) in granite*. We identified eleven pipeline-granite intersections in NC and southern VA along the Williams/Transco pipeline (completed) and the Atlantic Coast Pipeline (initial construction stage). We used the conceptual design for a mined cavern in granite in the Maryland piedmont developed by PB-KBB (1998) in a U.S. DOE sponsored study as an example of a natural gas storage cavern that could potentially be adapted for use in NC and VA granites*. In that study, a RMC plant with 5 BCF design capacity and storage cavern at a 3,000-ft. depth was estimated to cost $173 million ($1998). RMC facilities provide high deliverability and multiple injection/withdrawal cycles per year to meet multiple peaking and other short-term demands, and have a small above-ground footprint. RMCs would have a high level of physical security and could provide emergency supplies during natural or manmade supply disruptions. Liquefied Natural Gas (LNG) plants might have lower capital cost, but would be less physically secure, and more limited in their cycle time. GIS and Google Earth Pro were used to intersect granite outlines from USGS digital state geologic maps with pipelines. USGS search engines provided additional information on the granites identified. The USGS’ National Geologic Map Database provided search results for geological, geophysical, and geochemical maps. Existing geological knowledge of granite rock locations with potentially suitable geotechnical properties in NC and southern VA, and modern advances in hard rock excavation technology, argue for the overall technical viability of the RMC concept. Commercial viability will depend on site specific conditions, market analysis, and other considerations. If the need for underground storage along the U.S. eastern seaboard justifies the higher costs of underground excavations, such as the type described by PB-KBB corporation, the granites would warrant further consideration as underground storage sites. The same argument might apply to granite terrains in other global regions undergoing an expansion in natural gas use. *Granite as used herein is a broad term for massive and isotropic rock bodies with physical and mechanical properties capable of sustaining large underground openings.