Hurricanes' Thunder Felt in Gulf

4,000 Facilities Affected

The 2005 hurricane season plowed into the Gulf of Mexico with a destructive zeal reminiscent of the record-setting number of gales just a year earlier -- never a good omen for the vital Gulf drilling operations that provide so much of America's energy.

During June and July seven tropical storms already had tracked across the Atlantic, bringing the total for those two months to a new record high.

To date, Hurricane Dennis posed the greatest threat for offshore petroleum interests and residents of the surrounding Gulf area. As the earliest Category 4 hurricane ever confirmed in the Caribbean basin, Dennis ripped through the island countries of Haiti and Cuba, taking 32 lives in its furry. Once ashore in the United States, it would claim another five victims.

While Dennis was still four days out of the Gulf, evacuations of some 4,000 offshore oil and gas facilities -- roughly 35,000 people -- were initiated.

Meanwhile in Mississippi Canyon Block 778, about 150 miles southeast of New Orleans, the Thunder Horse semi-submersible platform was revving up to come online. Jointly owned by BP and ExxonMobil, Thunder Horse is the Gulf's largest oil and gas facility. Once fully operational, it is expected to generate 250,000 barrels of oil and 100 million cubic feet of gas every day.

With mooring lines anchored and hook-ups in place, the crew had completed most of the preliminary steps necessary to turn up production, save for the telemetry system. Now with Hurricane Dennis cutting a destructive course directly toward the Gulf, the order was given to shut in the wells and evacuate the facility.

Image Caption

No, Hurricane Dennis didn't cause Thunder Horse to list, although the timing of the incident may have caused some to jump to that conclusion.

Photo courtesy of Minerals Management Service

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The 2005 hurricane season plowed into the Gulf of Mexico with a destructive zeal reminiscent of the record-setting number of gales just a year earlier -- never a good omen for the vital Gulf drilling operations that provide so much of America's energy.

During June and July seven tropical storms already had tracked across the Atlantic, bringing the total for those two months to a new record high.

To date, Hurricane Dennis posed the greatest threat for offshore petroleum interests and residents of the surrounding Gulf area. As the earliest Category 4 hurricane ever confirmed in the Caribbean basin, Dennis ripped through the island countries of Haiti and Cuba, taking 32 lives in its furry. Once ashore in the United States, it would claim another five victims.

While Dennis was still four days out of the Gulf, evacuations of some 4,000 offshore oil and gas facilities -- roughly 35,000 people -- were initiated.

Meanwhile in Mississippi Canyon Block 778, about 150 miles southeast of New Orleans, the Thunder Horse semi-submersible platform was revving up to come online. Jointly owned by BP and ExxonMobil, Thunder Horse is the Gulf's largest oil and gas facility. Once fully operational, it is expected to generate 250,000 barrels of oil and 100 million cubic feet of gas every day.

With mooring lines anchored and hook-ups in place, the crew had completed most of the preliminary steps necessary to turn up production, save for the telemetry system. Now with Hurricane Dennis cutting a destructive course directly toward the Gulf, the order was given to shut in the wells and evacuate the facility.

Heeding the Call

The brute force of Hurricane Dennis smashed into the Florida Panhandle on July 10 as a Category 3 storm with torrential rains and high winds that uprooted trees, downed power lines and caused widespread flooding. Offshore facilities remained relatively unscathed, though, with the eye of the storm tracking over deep water roughly 120 miles east of the path Hurricane Ivan forged in 2004.

In contrast to Dennis, 150 platforms and 10,000 miles of pipeline were in the direct path of Ivan, which destroyed seven platforms and significantly damaged 24 others. The 2004 tempest wreaked havoc underwater, too, by triggering mudslides in the Mississippi River delta that damaged at least 13 pipeline systems. Another four large-diameter pipelines were shut in from other causes due to Category 4 Ivan.

Four months later, all 17 of these pipelines were still shut in and 16 of the 24 platforms remained off production.

Adding insult to injury, the steep downturn in production took its toll at the pump. U.S. oil imports reached a 30-year high due in large measure to Ivan and his sibling storms that unleashed their fury on the Gulf. Production capacity in this region that generates 30 percent of all oil and 10 percent of natural gas purchased by Americans was dramatically cut from shut-in wells due to the storm.

Throughout the country, the per-gallon cost at the pump was soon climbing to well over $2.

There may be some consolation in that Hurricane Dennis did not further slow the still recovering Gulf production -- but just as platform and pipeline operators were breathing a sigh of relief at Dennis' uneventful, open-water passing, a reconnaissance plane spied the unmanned Thunder Horse severely listing at a 20-degree angle.

Not since the P-36 in Brazil several years earlier had a platform tilted at such a steep descent. In the case of Thunder Horse, the natural assumption was that it was sent listing by the wrath of Hurricane Dennis -- but that assumption, according to the U.S. Department of the Interior's Minerals Management Service, is most likely a premature one.

"Hurricane Dennis passed very far to the east of Thunder Horse. Based on the mid-ocean data that we have seen from Dennis, I think that the only tie between the Thunder Horse listing and Hurricane Dennis is that the Thunder Horse was evacuated for Hurricane Dennis," says Chuck Schoennagel, MMS deputy regional director. "I don't think the storm itself had anything to do with the listing. That is still part of the investigation."

Watch for statements from BP, the U.S. Coast Guard and the MMS regarding the ongoing investigation into the cause of the Thunder Horse listing. At this point, one of the few certainties is that if the telemetry had been in place prior to the evacuation, there would be a better chance of pinpointing the cause and precise timing of the listing.

After days of pumping out water from the flooded platform, the Thunder Horse righted itself. It was designated as seaworthy and storm-safe just in time for the next Gulf event: Hurricane Emily.

Lessons Learned

Regardless of the cause, it is, at the very least, a fortunate coincidence that the Thunder Horse platform was unmanned at the time of listing. At the MMS "Offshore Hurricane Readiness and Recovery Conference" held a few weeks after the incident, the recent Gulf events made a dramatic backdrop for discussions on how to prepare for the unpredictable during the stormy season.

"Our primary message was that we were not happy that four semi-submersibles broke loose during Hurricane Ivan," Schoennagel reports. "We think (operators) need to go back and look at how those are moored. They've addressed part of it by adding GPS systems, so if one broke loose, it could be tracked at all times.

"We have several studies that have been initiated to look at what occurred as a result of Ivan, and that's where we'll learn the lessons."

In addition to mooring procedures, the MMS is scrutinizing the design of pipelines in mudslide-prone areas and the fastening down of drilling units on fixed and floating production facilities.

In the meantime, platform and pipeline operators in the Gulf of Mexico will likely do as their onshore neighbors and brace for a hurricane season that is expected to generate a total of roughly 18 tropical storms, with nine of those potentially morphing into hurricanes and five to seven of those into major hurricanes. Such water-spawned violence generally occurs in 25-year cycles, according to the National Oceanic and Atmospheric Association.

The U.S. Atlantic Coast and Gulf of Mexico currently are at the crest of that cycle.

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