EIA's two metrics for assessing underground working natural gas storage capacity in the lower 48 states, US, showed mixed results for 2020 compared with 2019. Design capacity reported a small increase, and demonstrated peak capacity reported a small decrease.
Design capacity, sometimes referred to as nameplate capacity, is based on the physical characteristics of the reservoir, installed equipment, and operating procedures on the site, which often must be certified by federal or state regulators. Design capacity was calculated as the sum of the reported working natural gas capacities of the 387 active storage fields in the lower 48 states as reported on ‘Form EIA-191’, Monthly Underground Natural Gas Storage Report, as of November 2020. The 25 inactive fields in the lower 48 states were excluded from the total. The design capacity metric is a theoretical limit on the total amount of natural gas that can be stored underground and withdrawn for use.
Demonstrated peak capacity, or total demonstrated maximum working natural gas capacity, represents the sum of the largest volume of working natural gas reported for each individual storage field during the most recent five-year period, regardless of when the individual peaks occurred. In this report, the most recent demonstrated peak covers the November 2020 report period (December 2015 through November 2020). Demonstrated peak capacity is based on survey data from ‘Form EIA-191’ and is typically less than design capacity because it relates to actual facility usage, rather than potential use based on the design of the facility.
Natural gas design capacity was essentially unchanged in 2020; however, some operators revised earlier estimates, increasing working gas capacity. Design capacity of underground natural gas storage facilities in the lower 48 states increased by 4 billion ft3, or 0.1%, in the November 2020 report period compared with the November 2019. A couple of notable revisions increased working gas capacity reported for 2019 in the Mountain and Pacific regions, which reflects the operators’ reassessments of the operational characteristics of the affected fields.
In the Mountain region, Spire Storage West revised the working gas capacity at the Belle Butte field (formerly Ryckman Creek) up by 16 billion ft3 to 35 billion ft3 as of February 2019. Spire Inc. acquired Ryckman Creek Resources and Clear Creek Storage in Wyoming in 2018. After this acquisition, Spire Storage West reported reduced working natural gas capacity at the Belle Butte (formerly Ryckman Creek) field by 16 billion ft3. The field’s estimated operational capacity in 2019 was 19 billion ft3, compared with 35 billion ft3 in 2018. However, Spire Storage West has since decided to operate the Belle Butte field at the FERC-authorised working gas capacity of 35 billion ft3. Aside from this revision, working gas capacity remained unchanged in the Mountain region during 2020.
Working natural gas design capacity increased by 5 billion ft3 in the South Central region. The most notable increase in the region was the 4.2 billion ft3 gain reported for the Egan Storage Dome by Egan Hub Partners. Dewatering the salt cavern raised the capacity of this field.
In the Pacific region, the Northwest Natural Gas Co. revised the working gas capacity for the Mist field in Oregon, increasing capacity by 1.5 billion ft3 to 4 billion ft3 for 2019. The North Mist capacity expansion came online in May 2019. Northwest Natural revised its early estimates of the design capacity of the Mist field – the only new natural gas storage reservoir to come online in 2019 – based on the observed operational characteristics of the facility. Working gas capacity remained unchanged at the facility in 2020.
Demonstrated peak capacity decreased in 2020 as the decline in the Pacific region more than offset gains reported in other regions. Overall, demonstrated peak capacity declined by 8 billion ft3, despite reported increases in five of six regions in the lower 48 states as of the November 2020 report period compared with the November 2019 report period. Despite the net decline in demonstrated peak capacity for the lower 48 states, the overall trend was toward increased usage of natural gas storage and higher working natural gas storage levels for the second year in a row.
Demonstrated peak capacity declined by 34 billion ft3 in the Pacific region because previous peak levels – predating the 2015 natural gas leak at the Aliso Canyon natural gas storage facility in California – are no longer included in the five-year range (December 2015 – November 2020). The Aliso Canyon field has operated at reduced levels since coming back online following the leak. Despite the decline in demonstrated peak capacity for the region, natural storage facilities in the Pacific region also saw increased usage during 2020 like in the other regions.
The South Central region reported the biggest increase in demonstrated peak capacity in 2020, increasing 10 billion ft3 (0.7%) over the previous year. Salt facilities accounted for 8 billion ft3 of this year-over year increase. The Midwest had the next largest increase at 7 billion ft3, followed by the Mountain region at 7 billion ft3 and the East region at 3 billion ft3.
In recent years, several offsetting trends have affected the industry’s decisions about changes to underground storage capacity levels. Several recent trends may have reduced the need for investment in additional underground storage:
- Although natural gas production declined in 2020, overall higher levels of natural gas production compared with a few years ago may have reduced some customers’ need to withdraw from storage to meet their natural gas needs. Increased output in the Appalachian Basin, the Permian Basin, and the Haynesville shale formation has driven production growth.
- In recent years, natural gas prices have fallen and become less volatile.
- The seasonal spread between summer and winter natural gas prices has become increasingly smaller, reducing economic incentives to inject natural gas into reservoir and aquifer storage.
- Midstream infrastructure buildout (such as pipelines and compressor stations) has enhanced grid interconnectedness and flexibility, allowing natural gas to more easily reach end users.
On the other hand, other factors could increase the need for additional storage:
- Increasing exports of natural gas also could increase natural gas storage capacity in the Gulf Coast region to support pipeline exports of natural gas to Mexico and liquefied natural gas (LNG) exports.
Working natural gas in storage reached its highest level since 2016: Working gas stocks ended the November 2020 report period at its highest level since 2016, despite decreased natural gas production and continued high demand for natural gas in electricity generation and for export. The higher natural gas storage level was partly because working gas entered the refill season, in April, at 2006 billion ft3 – its highest level since 2017– following a relatively mild winter.
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