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About U.S. Natural Gas Pipelines - Transporting Natural Gas           
 based on data through 2007/2008 with selected updates

Natural Gas Pipeline Capacity & Utilization
Overview | Utilization Rates | Integration of Storage | Varying Rates of Utilization | Measures of Utilization

Overview of Pipeline Utilization

Natural gas pipeline companies prefer to operate their systems as close to full capacity as possible to maximize their revenues. However, the average utilization rate (flow relative to design capacity) of a natural gas pipeline system seldom reaches 100%.   Factors that contribute to outages include:

  • Scheduled or unscheduled maintenance
  • Temporary decreases in market demand
  • Weather-related limitations to operations

Most companies try to schedule maintenance in the summer months when demands on pipeline capacity tend to be lower, but an occasional unanticipated incident may occur that suspends transmission service.  

Utilization Rates

Utilization rates below 100% do not necessarily imply that additional capacity is available for use.  A pipeline company that primarily serves a seasonal market, for instance, may have a relatively low average utilization rate especially during the summer months. But that does not mean there is unreserved capacity on a long-term basis. 

On the other hand, during periods of high demand for natural gas transportation services, usage on some portions of a pipeline system may exceed 100% of certificated capacity.  Certificated capacity represents a minimum level of service that can be maintained over an extended period of time, and not the maximum throughput capability of a system or segment on any given day. 

Exceeding 100% of capacity is accomplished by secondary compression and/or line packing, which means that compression is increased, within safety limits, to raise throughput temporarily.  

Integration of Storage Capacity

Integrating storage capacity into the natural gas pipeline network design can increase average-day utilization rates.  This integration involves moving not only natural gas currently being produced but natural gas that has been produced earlier and kept in temporary storage facilities.

Interregional Transmission Pipeline Capacity Levels
                  click to enlarge

More information related to pipeline capacity and utilization…

States Dependent on Interstate Pipelines - map
Major Transportation Corridors - map

Major Interstate Pipeline Companies - table
Pipeline Mileage by State & Region - table

Interstate Pipeline Capacity on a State-to-State Level - spreadsheet

         Other Natural Gas Transportation Topics:

  Interstate - Pipeline systems that cross one or more States
- Pipeline systems that operate only within State boundaries
  Network Design - Basic concepts and parameters
  Regulatory Authorities
  Transportation, Processing, & Gathering
  Transportation Corridors - Major interstate routes
  Underground Natural Gas Storage - Includes regional discussion
  Pipeline Development & Expansion
  U.S./Canada/Mexico Import & Export Locations

Storage is usually integrated into or available to the system at the production and/or consuming end as a means of balancing flow levels throughout the year.  Trunklines serving markets with significant storage capacity have greater potential for achieving a high utilization rate because the load moving on these pipelines can be leveled.  To the extent that these pipelines serve multiple markets, they also can achieve higher utilization rates because of the load diversity of the markets they serve. 

Varying Rates of Utilization

Trunklines, which are generally upstream (closer to) the natural gas production fields and storage areas, may sometimes exhibit peak period utilization rates exceeding 100% because they are occasionally capable of handling much larger volumes than indicated by the operational design certificated by FERC.  

Utilization on the grid systems, which are closer to the consuming market areas and downstream of the storage fields, is more likely to reflect a seasonal load profile of the market being served.  The grid-type systems usually operate at lower average utilization levels than trunklines and usually show marked variation between high and low flow levels, reflecting seasonal service and local market characteristics. 

Measures of Pipeline Utilization 

There are several ways that natural gas pipeline system utilization may be estimated, as demonstrated in the following cases:

  • As a measure of the average-day natural gas throughput relative to estimates of system capacity at State and regional boundaries   
  • The systemwide pipeline flow rate, which highlights variations in system usage relative to an estimated system peak throughput level
  • A system peak-day usage rate, which generally reflects peak system deliveries relative to estimated system capacity  

The latter measure is a good indication of how well the design of the system matches current shipper peak-day needs. For example, when a pipeline shows a comparatively low average usage rate (based on annual or monthly data) yet shows a usage rate approaching 100 percent on its peak day, it indicates that the system is called upon and is capable of meeting its shipper's maximum daily needs. Nevertheless, a large spread between average usage rates and peak-day usage rates may indicate opportunities to find better ways to utilize off-peak unused capacity.

In some cases, utilization rates exceeding 100 percent may be an artifact of the data that obscures the true operational status of the pipeline. In some instances the sum of individual transportation transactions may exceed pipeline capacity even though physically the pipeline may not be full. For example, suppose a segment from points A to D (with points B and C between A and D) has a capacity of 200 million cubic feet (MMcf) per day. Suppose further that this segment handles a 100 MMcf per day transaction from A to B, a second of 100 MMcf per day from B to C, and a third of 100 MMcf per day from C to D. The pipeline company will report transportation volumes of 300 MMcf per day, even though its capacity is 200 MMcf per day but is only 50 percent utilized on any one segment.