Moving Natural Gas

Penn State Extension educator, Dave Messersmith, answers common questions regarding pipeline infrastructure in this two part article.
Moving Natural Gas - Articles


How do you pump natural gas for hundreds of miles?

Compressor stations are an integral part of the natural gas pipeline network that moves natural gas from individual producing well sites to end users. As natural gas moves through a pipeline, distance, friction, and elevation differences slow the movement of gas, and reduce pressure. Compressor stations are placed strategically within the pipeline network to help maintain the pressure and flow of gas to market. Natural gas within an interstate pipeline is generally already pressurized at 800 to 1,400 psi. To ensure that gas continues to flow optimally, compressor stations are placed typically 40 to 70 miles apart along the pipeline to provide a boost in pressure.

How does PA's projected interstate pipeline growth compare to other states?

There is no doubt we are in the midst of a historic level of natural gas pipeline development, not only in Pennsylvania but throughout the eastern US. These projects are being planned as a way to move natural gas from the productive Marcellus and Utica shale regions to markets throughout the East Coast. Penn State's Marcellus Center for Outreach and Research recently mapped the current slate of proposed natural gas transmission line projects. The mapped projects represent 2,927 miles of new pipeline, with construction reaching into ten states. Combined, the proposed projects would have the ability to move 16.8 billion cubic feet (BCF) of natural gas per day plus 120,000 barrels/day of natural gas liquids such as propane and ethane out of the Marcellus shale. This represents significant additional takeaway capacity considering daily production in the Appalachian Basin is currently around 17 BCF. Six of the projects would originate in Pennsylvania's Northern Marcellus production area and seven, including two liquids pipelines, would originate in the Western PA, Ohio and West Virginia tri-state area. Anticipated in-service dates for the majority of these proposed projects are late 2017 into 2018.

Do you think natural gas is 'here to stay'? Why natural gas instead of other energy sources?

It certainly appears like natural gas is here to stay - at least for the next several decades. In its 2015 Annual Energy Outlook the US EIA forecasts US natural gas consumption will grow by 3.5 trillion cubic feet (TCF) to a total of 29.7 TCF by 2040. The largest growth areas are expected to be in natural gas used for electric power generation and manufacturing and industrial uses. We will also begin to see growth in natural gas exports via pipeline to Mexico and global LNG exports from several US ports. Exactly how much natural gas exports will grow is difficult to predict. In the current climate of low global oil prices, LNG exports from the US are likely to be minimal. Should oil prices rise significantly we could see dramatic growth in LNG exports.

In electric power generation, natural gas is seen as a good fit with renewables such as wind and solar. Natural gas-electric generation can provide a baseline power source 24/7 while producing one half the CO2 emissions of coal-electric generation. It can also ramp up quickly on days when renewables cannot meet demand. So as we look to the future, and the continued development of wind and solar, a synergy is likely to develop between natural gas and non-fossil fuels.

How long does the pipeline itself last? What happens when it needs to be replaced?

Pipelines are engineered and built to last for generations. There are a number of major natural gas transmission lines in Pennsylvania that have been in continuous service, without incident, since the 1940's.

How do companies monitor the safety of a pipeline? What tools might they use?

Pipeline operators regularly inspect their pipelines for corrosion and defects. This is done through the use of pipeline integrity gauges or 'pigs'. Pigs are devices that are propelled down pipelines to clean and evaluate the interior of the pipe. Pigs can test pipe thickness and roundness, check for signs of corrosion, and detect leaks and other defects along the interior of the pipeline that may either impede the flow of gas or pose a safety risk for the operation of the pipeline. Sending a pig down a pipeline is fittingly known as "pigging".

In addition to inspection with pigs, a number of safety precautions and procedures are in place to identify potential concerns and minimize the risk of pipeline failures. A few of the safety precautions associated with natural gas pipelines include:

  • Aerial patrols: Planes are used to ensure that no construction activities are taking place too close to the route of the pipeline, particularly in residential areas. Unauthorized construction and digging is the primary threat to pipeline safety.
  • Leak detection: Natural gas detecting equipment is periodically used by pipeline personnel on the surface to check for leaks. This is especially important in areas where the natural gas is not odorized.
  • Gas sampling: Routine sampling of the natural gas in pipelines ensures its quality and may also indicate corrosion of the interior of the pipeline or the influx of contaminants.
  • Preventative maintenance: This involves the testing of valves and the removal of surface impediments to pipeline inspection.

What might cause a pipeline to fail/explode? When there is an explosion, how it is put out?

If there is a failure, valves are closed stopping the flow of any combustible material to the site. Local first responders are called upon to evacuate the area and maintain a perimeter.

It's important to recognize that natural gas transmission lines have an excellent safety record in Pennsylvania. The Pipeline and Hazardous Materials Safety Administration (PHMSA), which regulates transmission line safety and conducts incident investigation, maintains records on the industry dating back to 1970. There are over 10,000 miles of natural gas transmission pipelines in the Commonwealth. During the last 20 years, there were an average of 2.6 incidents per year in the state with three reported injuries and no fatalities.

If we look more closely at the PHMSA data we see that materials failures and corrosion are the leading causes of natural gas transmission line failures in Pennsylvania. So while the industry's track record is good, it's important for the industry to continue to develop inspection and maintenance procedures to identify and repair these areas of pipe before they can fail.

Are pipeline's ever taken out of service? What happens when/if a pipeline is taken out of service? Why would it be taken out of service?

Pipelines can be taken out of service if there is no longer a need for the pipeline. If it's an interstate natural gas transmission line, the Federal Energy Regulatory Commission (FERC) is involved in decommissioning the line and can place conditions on the pipeline operator to remove the pipe and restore the right of way. A landowners easement agreement may also stipulate whether the pipe is removed and site restoration processes.

What we see more commonly are pipelines being upgraded or re-purposed to transport another material rather than be completely removed from service. An example of this is Sunoco Logistics Mariner East pipeline stretching east to west across southern PA. The Mariner East once carried liquid petroleum products (gasoline, home heating fuel, etc.) but is undergoing a series of upgrades and expansions so that it can move natural gas liquids such as ethane and propane from the Western Pennsylvania to the refinery at Marcus Hook.

When a pipeline crosses a property, what are some things landowners need to keep in mind?

For example, can livestock still graze over the right of way? Can property owners ride ATVS over the right of way? What about planting near the right-of-way?

It's important for landowners to understand the pipeline operator's guidelines for property use and construction near natural gas pipelines and equipment. Normal gardening and agricultural activities such as cropping and grazing within the right of way are generally acceptable. However, landowners should never dig or construct anything within the easement without first having a pipeline representative mark the pipeline, stake the right of way, and explain the company's construction guidelines. Generally, property owners are prohibited from installing any structures, storing anything that could be an obstruction, or planting trees or shrubs within the right-of-way. Unauthorized building or planting in the pipeline right-of-way is known as right-of-way encroachment and may interfere with operation, inspection or maintenance of the pipeline.