Duke Energy Gas Transmission (DEGT) reported last Tuesday that it resumed operations at two of the three storage caverns that were taken out of service following the explosion and fire at its rural Liberty County, TX, facility in mid-August.

DEGT, a subsidiary of Duke Energy, received approval on Oct. 28 from the Texas Railroad Commission (RRC) to return caverns Nos. 2 and 3 at its Moss Bluff salt cavern storage facility to partial service, said company spokesman Danny Gibbs. The two caverns, which have working gas capacity of about 12 Bcf, were largely unaffected by the blast and subsequent fire.

Moss Bluff customers will be allowed to make full withdrawals from the site, but they can only make limited injections, he noted. Customer injections will be restricted to 50% of their maximum daily injection quantity until further notice, the company said.

Gibbs said the limitation on injections would be lifted once the mechanical restrictions of the caverns are addressed, but he could not say when that would be. Nor did he know when the affected cavern No. 1, the site of the seeping natural gas, would be returned to service. He ventured it would be “sooner rather than later.”

As for cavern No. 1, Gibbs said the above-ground infrastructure sustained the most damage, not the cavern itself.

The fire, which burned for an entire week, broke out in the pre-dawn hours of Aug. 19 following an explosion in cavern No. 1, which held 6 Bcf of stored gas. No one was injured in either the blast or subsequent fire.

In early October, DEGT reported to Texas regulators that a series of unusual events, some with unknown causes, led to the out-of-control gas leak and fire at cavern No. 1 at its Moss Bluff facility. The company said the “initiating event” was a “separation” on the 8 5/8 inch brine disposal pipe at a depth of about 3,724 feet that allowed gas to seep into the pipe, flow into an above ground eight-inch diameter pipe and then trigger an emergency shut down (ESD). The resulting mechanical forces produced by the sudden surge of flow caused the eight-inch piping between the wellhead and the ESD valve to breach, causing the fire, according to Duke.

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