Peak working capacity of underground gas storage for the Lower 48 was an estimated 4,049 Bcf in April, up 4.1% compared with 3,889 Bcf in April 2009, the Energy Information Administration (EIA) said Friday. Working design capacity was 4,364 Bcf, a 1.2% increase from last year, EIA said.

Peak working capacity is based on actual peak storage volumes, while working gas design capacity is based on certificated capacity.

"During the past year, the increase in natural gas storage capacity estimates can be attributed to the opening of new facilities, capacity expansion at existing facilities and, for demonstrated peak capacity, greater use of existing storage facilities during the past year," EIA said in the 2010 update.

Peak working capacity was equivalent to 92.9% of working design capacity across three storage regions, a 2.7% increase compared to April 2009 that was driven in large part by a 6.3% increase in the West. But peak working capacity represents just 79.6% of working design capacity in the West, significantly lower than the East (96.3%) or the Producing region (93.8%), according to EIA.

"The West has several still-active fields whose primary role is not seasonal storage," EIA said. "These include fields used for pipeline load balancing and fields that are being drawn down to be taken out of service. Additionally, some fields in the West have large design capacities but have infrastructure constraints that limit actual storage capacity."

End-of-month working gas inventories reached all-time highs last fall, with stocks for the Lower 48 at the end of November 2009 climbing to 3,833 Bcf, EIA said (see NGI, Nov. 16, 2009). According to EIA, increased working gas design capacity, robust production coupled with declining demand, high starting inventory levels and a favorable pricing environment all led to last year's record inventories.

With working inventory at the end of October projected to be 3,752 Bcf -- just 2.1% less than last year -- that scenario could be repeated this year, EIA said.

"Storage operators appear on pace to approach these all-time high levels for working gas in storage in the fall of 2010."

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