Natural gas storage capacity nearly unchanged nationally, but regions vary

U.S. natural gas working storage capacity (in terms of design capacity and demonstrated maximum working gas volumes) as of November 2015 was essentially flat compared to November 2014, with some regions increasing while others decreased. Demonstrated maximum working gas levels increased in the South Central Salt region, offsetting declines in the Mountain region. With the exception of the Mountain region and the South Central region, storage capacity in most regions changed by less than 1% from the previous period in both maximum working gas levels and in design capacity. These relatively small changes in natural gas storage capacity occurred during the following market conditions:

• The 2015 injection season beginning with working natural gas storage levels below the five-year average
• Continuing growth in production displacing some amount of withdrawals
• An unseasonably warm early winter in October and November 2015 reducing early withdrawals
• Storage reaching record high levels in November 2015
• The Henry Hub spot price hovering between $2.00 and $3.00 per million British thermal unit for almost all of 2015

The U.S. Energy Information Administration (EIA) uses two distinct measures of natural gas storage capacity:

Demonstrated maximum working gas volume: This measure represents the sum of peak volumes reported by the 385 active storage facilities (as of November 2015) in the Lower 48 states, regardless of when the individual peaks occurred over the most recent five-year period (covering December 2010 - November 2015).

The total demonstrated maximum working gas volume, or demonstrated peak, in the Lower 48 states was nearly unchanged between November 2014 and November 2015, rising by just 0.1%, or by 6 billion cubic feet (Bcf), to 4,343 Bcf. This period featured a substantial decrease in the demonstrated peak for the Mountain region, which was more than offset by a substantial increase for the South Central Salt region.

The Mountain region showed a demonstrated peak of 274 Bcf, 18 Bcf lower than the previous period, a decrease of 6.3%. Almost all of this decrease can be attributed to two facilities that hit their respective demonstrated peaks between December 2009 and November 2010, months that were not included in the November 2015 demonstrated peak figures. These two facilities accounted for 17 Bcf of the reduction in demonstrated capacity from the region between November 2014 and November 2015.

In the South Central Salt region, by contrast, the new demonstrated peak was 436 Bcf, an increase of 24 Bcf, or 5.8%, compared with the previous period. This increase is attributed to three facilities that reached their new five-year peaks in November 2015.

A total of 10 facilities became inactive this year, which removed about 12 Bcf from the demonstrated peak total. A facility is generally marked inactive after a full year without any injection activity, or when the company declares that a storage field is in the process of depletion or abandonment.

Design capacity: This measure is the sum of the 385 active storage fields' working gas design capacity, as of November 2015, as reported on survey Form EIA-191, Monthly Underground Natural Gas Storage Report. Design capacity is based on the physical characteristics of the reservoir, installed equipment, and operating procedures particular to the site, and is often certified by federal or state regulators.

The total design capacity in the Lower 48 states was also nearly unchanged between November 2014 and November 2015, declining by just 0.2%, or 7 Bcf, to 4,658 Bcf.

The modest change in capacity this period is mainly the result of the deactivation of 10 storage fields, which removed 16 Bcf of storage capacity from service.

Most of the storage regions had relatively stable capacity year-on-year. The East region had the largest volumetric and percentage change, losing 12 Bcf of design capacity, equal to 1.1% of the region total, and now stands at 1,032 Bcf. About half of this capacity loss resulted from four fields becoming inactive between December 2014 and November 2015.

The largest single field to become inactive was in the South Central Salt region -- the Bridgeline Napoleonville field in Louisiana, with a capacity of about 7 Bcf. This decrease largely offset an expansion at the Bobcat Port Barre field, also in Louisiana, which increased its capacity by 5 Bcf over the period.

Despite featuring the largest increase in demonstrated capacity between November 2014 and November 2015, design capacity of the South Central Salt region was essentially flat for the period, decreasing by just 1 Bcf, or 0.3%, to 480 Bcf.

High storage volumes: National working gas storage volumes hit record high levels in November 2015, reaching the highest-ever weekly volume of 4,009 Bcf for the week ending November 20. The Midwest, South Central, and South Central Salt regions all hit record levels that week, while other regions were generally near record levels. These high levels resulted from the unusually warm weather for the period, in addition to production growth despite low natural gas prices.

No new underground storage facilities: For the second consecutive year, no new storage facilities have begun operation. Increases in working gas design capacity for the period came from expansions to existing fields. A total of 12 facilities expanded capacity by 1 Bcf or more between December 2014 and November 2015, averaging about 2 Bcf additional capacity each. Expansions were concentrated in the Midwest, where 9 of the 12 expansions occurred. All of the Midwest expansions were in depleted reservoirs. The largest expansion in the Lower 48 states was at the Bobcat Port Barre field in the South Central Salt region, which completed the addition of a fourth cavern for an increase of more than 5 Bcf.

Estimates of Underground Natural Gas Storage Demonstrated and Design Capacity, as of November 2014 and November 2015 (billion cubic feet, unless otherwise noted)
	Demonstrated Maximum Working Gas Volume1			Working Gas Design Capacity2			Demonstrated Maximum Working Gas Share of Working Gas Design Capacity
Region	(Dec 2009 - Nov 2014)	(Dec 2010 - Nov 2015)	Percent Change	Nov 2014	Nov 2015	Percent Change	Nov 2014	Nov 2015
East	1,000	994	-0.7%	1,044	1,032	-1.1%	96%	96%
Midwest	1,179	1,188	0.7%	1,218	1,226	0.7%	97%	97%
Mountain	292	274	-6.3%	464	462	-0.6%	63%	59%
Pacific	407	411	0.9%	415	416	0.3%	98%	99%
South Central	1,458	1,477	1.3%	1,524	1,521	-0.2%	96%	97%
Salt	412	436	5.8%	481	480	-0.3%	86%	91%
Nonsalt	1,046	1,041	-0.4%	1,043	1,042	-0.1%	100%	100%
Lower 48	4,336	4,343	0.1%	4,665	4,658	-0.2%	93%	93%
Sources: Form EIA-191, Monthly Natural Gas Underground Storage Report Note: Design capacity information for all facilities, including inactive fields, is available in the Natural Gas Annual Respondent Query System. Monthly data are available for January 2015 on. Totals may not equal sum of components because of independent rounding. Information about storage regions is available at Storage Basics. Mentions of specific companies in this report include only information that is already publicly available in EIA's query system. (1) Demonstrated maximum working gas volume is the sum of the highest storage inventory levels of working gas observed in each distinct storage reservoir over the previous five-year period as reported by the operator on the Form EIA- 191, Monthly Underground Gas Storage Report. The timing of the peaks for different facilities need not coincide. Inactive fields were removed from aggregate statistics. (2) Working Gas Design Capacity is an estimate of a natural gas facility's physical working gas capacity as reported by the operator on the Form EIA-191 Monthly Underground Gas Storage Report. It represents the sum of all fields' capacities at a point in time. It is a measure based on the physical characteristics of the reservoir, installed equipment, and operating procedures particular to the site that is often certified by federal or state regulators. Inactive fields were removed from aggregate statistics.

As with last year, most currently planned storage projects are concentrated in salt formations, likely because of their high deliverability rates. Salt domes are capable of sending out natural gas within a short time, sometimes within an hour, making them more responsive to customer demand than other types of underground storage.

In late 2015, EIA began publishing weekly data in five regions and historical data for the five region series back to 2010. The new regions were implemented in order to better group storage operators based on new market dynamics and field types. This change allows greater insight into storage movements by providing more localized data.