Types of Gas Pipelines
Essentially, three major types of pipelines occur along the transportation route: gathering lines, transmission pipelines, interstate pipelines, intrastate pipelines, and the distribution system. Gathering lines are small-diameter pipelines (2–20 inches) that move natural gas from the wellhead to a natural gas processing facility or an interconnection with a larger mainline pipeline. Transmission pipelines are wide-diameter (20–48 inches), long distance pipelines that transport natural gas from producing areas to market areas. Interstate pipelines are 8-24 inches in diameter and carry natural gas within a state and to adjoining states. Intrastate natural gas pipelines operate within state borders and link natural gas producers to local markets and the interstate pipeline network. Although an intrastate pipeline system is defined as one that operates totally within a state, an intrastate pipeline company may have operations in more than one state. As long as these operations are separate—that is, they do not physically interconnect—they are considered intrastate and are not jurisdictional to the Federal Energy Regulatory Commission (FERC), the agency that approves interstate pipelines. Distribution lines are smaller diameter lines that deliver the gas from the larger pipelines to the end users.
The type of pipeline (gathering line versus interstate transmission line) placed on a landowner’s property, influences the amount of surface disturbance (i.e., larger areas are disturbed when installing larger diameter pipelines) and determines whether eminent domain is possible and if regulatory oversight is at the state or federal level.
Natural Gas Liquids Pipeline
Natural gas production in parts of the Appalachian basin, especially in western Pennsylvania, Ohio, and West Virginia, are rich in natural gas liquids such as ethane, propane, and butane. These liquids are generally separated from the natural gas stream and shipped in dedicated natural gas liquids pipelines. Within the federal regulatory framework, natural gas liquids pipelines fall under the Interstate Commerce Act and are regulated the same as oil pipelines. This means that proposed gas liquids pipelines do not go through the FERC review process and, importantly, do not receive federal eminent domain authority. Interstate natural gas pipelines, on the other hand, are covered by the Natural Gas Act and go through the FERC process. The key factor in determining which regulations are followed is whether or not the product is liquid at standard pipeline pressures.
Natural Gas Storage Fields
It is also worth noting that natural gas and natural gas liquids can be stored in certain bedrock reservoirs, typically depleted gas fields or bodies of rock whose geological and engineering characteristics make them capable of storing injected natural gas and natural gas liquids. When gas demand is lower in the summer months the gas is injected into these deep reservoirs via injection wells and then pumped back out to meet peak demands in the winter. Pennsylvania has approximately 60 gas storage fields, mostly in western and northern Pennsylvania in areas of historic conventional oil and gas production. Pennsylvania has the fourth largest natural gas storage capacity in the nation with approximately 763 billion cubic feet(EIA, 2017), which is critical to meet peak gas demands in the winter months in the northeastern US.