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Natural Gas Infrastructure: Compressor Stations and Underground Storage Part 1

Posted: September 11, 2011

This first in a two-part series explains what role compressor stations and underground storage play in gas development.

Compression. Underground gas storage. Marcellus Shale.  What do these mean for the East Coast natural gas market? After having the opportunity recently to tour a Dominion Energy compressor and gas storage facility in western PA, my answer would be a lot.

Over the last 60-plus years, natural gas infrastructure has been installed in this part of the state, with interstate pipelines intersecting and traveling through southwestern PA to various compressor stations in the region. All of these contribute to some of the advantages western PA holds in the development of Marcellus Shale.

Compression of gas is required to increase or stabilize the pressure in interstate pipelines to ensure its delivery to markets of residential, commercial, and industrial customers in PA and beyond. Underground storage provides a place to “inventory” gas during periods when production is greater than demand, typically during the summer. When usage demands increase during the winter, this inventory is then tapped to meet those demands.

This compressor station was constructed during 1950-51 and currently employs about 90 individuals who work amid a complex of large pipelines and buildings stuffed full of giant engines, compressors, and electronic monitoring and control panels.  Interstate pipelines carry natural gas from outside the region as well as locally produced Marcellus Shale gas to this compressor station, with some gas being injected into the underground storage as inventory.

The underground storage area has a geographic footprint covering an area about 3 miles wide and 13 miles long. Natural gas, under pressure, is injected into 2 geological sand layers 1200-2200 feet underground. The gas is fed into these porous sands from about 360 wells spaced across the storage footprint. As it is injected into the sands, the natural gas migrates throughout the depth of the layer and equalizes in pressure.

How do they know where the gas is after injecting it underground, and why does it stay there? A series of strategically drilled “observation wells” located just outside the footprint of the gas storage area are continuously monitored by facility engineers to detect any pressure changes of the gas being stored, which could indicate that gas may be migrating outside the storage area. Additionally, a solid rock layer sits on top of and below the layers of sand storage, so natural gas does not have a chance to escape either up or down.

Stay tuned, because next time, we’ll talk about the compressor station component of this facility.

Jon Laughner, Penn State Extension, Beaver County