An early-morning explosion that jolted Duke Energy’s Moss Bluff underground salt cavern storage facility last Thursday in Liberty County, TX, took a turn for the worse in the pre-dawn hours Friday when an above-ground valve structure failed, causing a larger release of natural gas that shot flames 1,000 feet into the sky.

Despite this turn of events, Duke Energy expected the fire to “probably burn out” by early Saturday when the approximately 6 Bcf of stored gas being released from Cavern #1, the suspected source of the blast, was to have burned off. No damage was reported to the area surrounding the three-cavern storage site, located 40 miles northeast of Houston.

The valve structure collapsed at about 1:30 a.m. (CDT) Friday due to the intense heat from the fire, increasing the release of gas from Cavern #1 that has the capability to hold 8.7 Bcf (includes base and cushion gas). The flames soared from 100 feet to 1,000 feet as a result, and were said to be visible from Houston.

All Moss Bluff personnel on the site were accounted for following the valve structure failure, the company said. Only one employee was on duty at the time of the explosion on Thursday, but he was not injured. Duke Energy said it recommended to emergency personnel in both Liberty and Chambers counties that a three-mile area around the facility be evacuated.

It was assisting local sheriff’s departments on Friday in re-locating residents to either shelters or hotels, said Duke Energy spokeswoman Gretchen Krueger. The Duke Energy Foundation contributed $10,000 last week to the Greater Houston Chapter of the Red Cross to help with the evacuation efforts.

An investigation into the cause of the explosion was underway and damage assessments were continuing, Duke Energy said. The company notified the appropriate state and federal agencies, including the Federal Energy Regulatory Commission, the Department of Transportation (DOT) and the Texas Railroad Commission, Krueger said.

The Texas Railroad Commission is the lead agency in investigating the cause of the explosion, as well as assessing the impact of the blast/fire on the surrounding community and the pipelines that connect to the storage facility, said Damon Hill, a spokesman for DOT’s Office of Pipeline Safety (OPS) in Washington, DC. But “we are monitoring the situation.”

Firefighters from Boots & Coots returned to the scene Friday and were taking steps to try and cool the area and cut off gas to the blown-out valving, the Houston Chronicle reported.

Initial reports said the source of the explosion, which occurred at about 4:15 a.m. CDT Thursday, was in the cavern with 6 Bcf of stored gas. But “we have not confirmed that,” Krueger said. Two other nearby storage caverns at the site were not affected by the intense fire, but all storage withdrawals and injections were curtailed.

“There are no other concerns that this is going to move any further,” Liberty County Sheriff Bill Tidwell told NGI. It was “too early” to determine the cause, he said.

Moss Bluff issued a force majeure notice shortly after the blast, suspending operations “until further notice.” It said it “will keep its customers advised [of] the extent of the damage…and the prospects of returning to service.”

It’s “too early to speculate” as to how long service at the Moss Bluff storage facility will be interrupted, Krueger noted. Extinguishing the fire, assessing the damage and investigating the cause of the explosion were the company’s priorities now, she said. Duke Energy said it has standard general liability and property insurance and does not expect the episode to have a material financial impact.

The throughput on the five pipelines that interconnect with the Moss Bluff facility was not impacted, Krueger said. However, Texas authorities last week were concerned that the heat from the fire could cause connecting pipelines, which are located two to three feet underground, to rupture and ignite, the Houston Chronicle reported.

Pipes interconnecting with the storage operation include interstates Texas Eastern Transmission, which delivers gas to the Northeast, and Kinder Morgan’s Natural Gas Pipeline Co. of America, which supplies gas to the Midwest. Also interconnecting are intrastate pipes Channel Industries, Kinder Morgan Tejas Gas Pipeline and Kinder Morgan Texas Pipeline, all of which serve the Texas market.

There has been “no impact on meeting customer obligations” for the three Kinder Morgan lines, said spokesman Rick Rainey. The Kinder Morgan intrastate pipelines are storage customers of Moss Bluff, as well as providers of transportation service. “We will continue to evaluate [the situation],” he said, but it’s premature to talk about what action the Kinder Morgan pipes will take in the event Moss Bluff should remain closed for an extended period.

“We do have some flexibility on our system but it’s too early [to] speculate about long-term effects until we know the full impact to Duke’s operation,” Rainey told NGI.

Given the timing of the explosion — late summer vs. the dead of winter when gas supplies are stretched — the loss of stored gas at Moss Bluff was not expected to have a marked effect on the level of overall gas inventories. At most 5-6 Bcf of gas was burned up, while the Energy Information Administration last Thursday reported the industry injected thirteen times that amount (78 Bcf) into storage for the prior week, pushing total storage past the 2.5 Tcf mark.

The high-deliverability Moss Bluff storage facility serves 13 customers, including marketers, pipelines and local distribution companies, with 16 Bcf of working gas capacity from three caverns. The Moss Bluff storage site has a send-out capability of 1.2 Bcf/d, and is ranked 11th in the nation in terms of deliverability.

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