A winter heat source right under our noses
With winter half over, Greene County residents have already run into some below zero days. With more cold weather yet to come, those heating their homes and businesses with natural gas may wonder how supply keeps up with demand and how prices remain competitive at a time of greatly increased consumption.
The answer dates back to the 1930s, when Dominion Energy Transmission, Inc. (DETI) developed its first underground storage field in Bridgeport, W. Va. using former gas production wells that were depleted. The idea behind the storage field was to purchase gas in the summer, when prices are typically low, then store it in sandstone chambers (usually depleted gas wells) until demand increased during the cold winter months when distributors release it to the supply pipelines.
“In general, about 50 percent of the gas people use in winter comes from these underground storage fields,” said John Love, director of gas storage and land services for Dominion Energy Transmission, Inc (DETI).
The other 50 percent comes from production fields such as the Marcellus Shale, the Utica Shale, Appalachian conventional wells and the Gulf of Mexico.
A provider of gas transportation and storage services, DETI maintains 17 gas storage fields in three states. Pennsylvania holds 11 of them, West Virginia has four and New York has two. Typically, the fields are located in rural areas, away from big population centers, and all have compressor stations associated with them. One of the fields has only a handful of wells; most have dozens, even hundreds of wells.
DETI typically injects natural gas into its storage pools from April 1 to October 31. Customers – local distribution companies, industrials, power generators, marketers, etc. – typically purchase natural gas during this time of year when natural gas values are normally lower to prepare for the upcoming winter heating season (November 1 – March 31).
According to Frank Mack, DETI’s communications projects manager, Greene County has five relatively small storage pools: Pratt, Swarts, Swarts West, Hunters Cave and Holbrook, all operated by EQT. All five are thought to be active although Holbrook is the only one confirmed as being active. The only sizable storage field in Fayette County is North Summit in Hopwood, operated by DETI.
One of the largest storage compressor stations in the nation, the Oakford Station, is located along Route 22 near Delmont in Westmoreland County. With a storage capacity of 132 billion cubic feet of gas, the field has two sandstone formations which together run 4.5 miles east to west and 14.5 miles north to south. The Murraysville sandstone formation is, on average, 1,400 feet deep while the Fifth Sand lies approximately 2,250 feet below the surface. Interestingly, all of the storage pools in both Greene and Washington counties together would fit in a small corner of the Oakford Storage Pool.
Overall, DETI operates one of the nation’s largest underground natural gas storage systems – currently about 756 billion cubic feet (Bcf) of storage capacity, and has successfully and safely managed its natural gas storage facilities since it began storing natural gas for its customers in the 1930s.
The company is authorized by the Federal Energy Regulatory Commission to inject and withdraw about 420 Bcf of natural gas for its customers and storage partners. Most of the natural gas in its storage pools are for DETI customers, but in the larger storage pools, DETI has partners (Williams, Kinder Morgan) who also storage natural gas for their customers. DETI’s share of this top gas capacity is about 300 Bcf. To put 300 billion cubic feet in perspective, this volume would supply enough natural gas annually for 3.3 million residential homes, based on average usage according to the American Gas Association, 2015.
According to Mack, Dominion Energy has 3,900 miles of interstate natural gas pipelines in six states (NY, PA, Ohio, WV, MD and VA) as well as close to 450 employees in the Commonwealth of Pennsylvania and about 80 employees at Oakford, where they operate and maintain the pipelines, compression and gas storage fields. In addition, the Gas Storage group includes about 20 employees who provide geological, environmental and technical support to DETI’s 17 natural gas storage fields, including Oakford storage.
DETI has a variety of programs and methods to assess the integrity of its natural gas storage system. They include periodic inspections of the well casing for internal and external corrosion, regular inspections of its approximately 1,500 storage wells to verify well status, pressure, visual corrosion, vent gas and evidence of leaks and monitoring by the Gas Control Group and Operations field personnel.
With 5,400 customers in Greene County, People’s Natural Gas gets a portion of its supply from underground storage pools to meet winter demand and help keep costs low, although it has no storage pools in the county. Barry Kukovich, the company’s media relations representative, said its customers can now feel more secure than ever about getting a winter supply of gas due to Marcellus Shale drilling.
Gas storage also is used to provide natural gas supplies for a growing, year-round electric power-generation market to produce electricity, and during the summer months for cooling during those warm days.
With the current abundant supply of natural gas, over the past 17 years gas has surpassed coal in the generation of electrical energy. In 2001, coal supplied 51 percent of the nation’s electrical generation, according to the Energy Information Administration. That same year, natural gas generated 17 percent of the nation’s total electricity.
“Even with the significant increase over the past 15 years of our country generating more electricity with natural gas and less with coal, natural gas storage will continue to play an important role of meeting peaking demand during the winter heating season as well as during the summer,” Love said. “The significant amount of additional pipeline infrastructure that has been added to the nation’s pipeline network in recent years as well as what is currently under construction will serve to meet the majority of the growing need for electric generation in the future.”
In 2017, the percentages had changed in favor of national gas when it supplied 32 percent of the nation’s electricity. Coal had fallen to providing 30 percent of our electricity output. This trend comes at a time when it’s recognized that coal fired generation plants have a significantly higher level of emissions than gas fired plants.
“However, gas storage will continue to play an important role in helping to meet both winter peak demand and summer electric generation,” Love continued. “As more companies use natural gas to generate electricity, the more gas storage they use, typically the more price stability they will obtain. Whether it’s winter heating demand or summer electric power generation, it is imperative that the required incremental volumes of natural gas be reliably provided at the time they are needed. Natural gas storage will help to meet this need.”