Industry, government address MODU reliability issues

Dec. 14, 2005
Offshore oil and gas producers and drilling contractors are advancing their work with the federal government to address mooring reliability issues raised by recent Gulf of Mexico hurricanes.

Nick Snow
Washington Correspondent

WASHINGTON, DC, Dec. 14 -- Offshore oil and gas producers and drilling contractors are advancing their work with the federal government to address mooring reliability issues raised by recent Gulf of Mexico hurricanes.

Work got under way following Hurricane Ivan in 2004, which left five rigs adrift, and intensified following 2005's two major hurricanes, Katrina and Rita, in which 19 mobile offshore drilling units (MODUs) broke away.

"Ivan was the instigator of the process. Previous to it, we'd had some instances of mooring failures but none to the extent that occurred during that storm," said Rodney W. Eads, senior vice-president of worldwide operations at Diamond Offshore Drilling Inc. in Houston.

The industry thought its operating practices and standards for the gulf were sufficient before the 2004 storm, he said "Ivan caused us to reconsider that viewpoint, and as we did along came Katrina and Rita. To have a Category 4 storm followed by two Category 5's within a year is unprecedented," Eads said.

Before Ivan, there had been a lull in hurricanes since Andrew in 2002, when two rigs broke away, according to Bud Dannenberger, chief of engineering and operations for the US Minerals Management Service.

After the 2004 storm, industry and government groups agreed that changes were necessary and began gathering information, he said. MMS hosted a hurricane conference in Houston in July 2005 with the US Coast Guard, the American Petroleum Institute, and the International Association of Drilling Contractors.

The issue immediately attracted the attention of senior officials from industry and the government, said Betty Anthony, API's upstream, marine, pipeline, and membership group director.

"No one, whether it's the government, the producers, or the drilling rig owners and operators, wants to see a serious impact from the rigs if they move during a hurricane. Everyone wants to increase the rigs' reliability," she said.

Consensus
Participants emerged from that Houston conference with a general sense that improvements had to be made, Dannenberger said. "Hurricanes Katrina and Rita made it a consensus."

Danny McNease, chairman and chief executive of Rowan Cos. Inc., said, "We're moving ahead. We already had a lot of studies under way before these last hurricanes on the jack up side and hope to have some ideas before this next hurricane season on how to improve our operating capability."

Producers and drilling contractors that work in deeper water in the gulf had launched their own program following Hurricane Ivan, the MODU Mooring Reliability and Risk Assessment Joint Industry Project, sponsored by the Offshore Operators Committee, IADC, and API, Eads said.

"The industry approach is generally two-fold for the moored MODUs. First, it wants to do everything practical to increase the strength of the existing mooring systems. Second, it wants to evaluate adding additional mooring lines to increase the strength of the total mooring system," he said.

Anthony said Gulf of Mexico operators had designed this approach before presenting it to government regulators during a Nov. 17 meeting at Interior Sec. Gale A. Norton's office.

"The meeting was to explain to the government what the industry was doing to increase the reliability of mooring systems," Eads said. "It showed that we're working together and have a plan that we are implementing."

Anthony said the goal is to accelerate industry research and produce an interim report by March and a final report of the joint industry project by the end of 2006.

"If we get to a point that we have significant information suggesting that industry standards need to be reexamined, we will do that on an expedited basis. API has a standards-setting body for just that purpose," she said.

Drilling contractors also have been examining causes that led to 19 rigs breaking away during Hurricanes Katrina and Rita, Dannenberger said. "There were excursions from just a few hundred feet to a hundred miles," he said, adding that the drillers would submit initial reports to the MMS later in December.

"They all have plans to improve their fleets and improve their mooring capabilities, and this will give them a chance to let us know where they are in the process," he said.

Immediate steps
Offshore drillers also are examining steps they can take before the next hurricane season, such as developing optimal mooring design patterns—symmetrical or asymmetrical—and whether they could survive in shallower water, and other considerations, according to Dannenberger.

"Also being discussed is monitoring the rigs after they've been evacuated. Virtually all of the drilling contractors have the capability to position the rigs, but we think it might be helpful to monitor the anchor tension forces after the rigs have been evacuated," he said.

McNease said: "Overall, jack ups did well. We're evaluating why there were failures. It could be many different things. The foundation may have collapsed from the force of the hurricane, causing it to turn over. In other cases, the storm was so strong in certain areas that it exceeded the drilling unit's capability."

Participants agree, however, that improving mooring reliability standards and practices for MODUs in the gulf won't be easy.

"One important point is the number of different rig types, and each hurricane's unique characteristics," Anthony said. "Ivan had a number of undersea mudslides, for example. People are looking now exactly at what conditions were encountered during Katrina and Rita."

She noted that some production platforms in the two 2005 storms' paths were able to collect weather data, including the types of sustained wind and their duration.

"Everyone is trying to collect information about the actual conditions and factor that into what can be done if conditions like this occur more frequently, particularly in terms of changing designs," she said.

Offshore drillers have had access to equipment capable of withstanding harsh conditions in the North Sea and other regions for years, Dannenberger said.

"The big difference is that the average conditions in the Gulf are rather benign. Then you can get a big jump to hurricane conditions, which are beyond conditions in regions like the North Sea," he said.

Unpredictability, intensity
Eads said the key difference between hurricanes and harsh conditions in other areas is unpredictability. "There also is the issue of intensity," he said. "When you get a Category 5 storm in the gulf, you're facing something you would rarely find in the North Sea."

McNease said: "In the North Sea, you continuously operate in a harsh environment. That's where we use our Gorilla rigs. In the Gulf of Mexico, you're looking for the jack up to survive instead of operate. In this case, the storms exceeded the survivability of the rigs."

When a gulf jack up is in full operating mode, he explained, employees are present, working under normal conditions. During a major storm, those employees have been evacuated, and the rig is in a survival state, but its onboard equipment is still gathering information.

Some possibilities are emerging, McNease said. "We believe we can increase the air gap and improve the survivability of the units. We're also looking at better weather data. We're also looking at foundation failures and solving that problem. We do that by getting additional core data as we move rigs to a site and determine whether it can survive a storm," he said.

Anthony said, "We don't know, but there has been discussion about our entering a different kind of hurricane cycle than in the past 20 years. If our existing data are different, what questions does this pose for retrofitting and designs going forward?"

Contact Nick Snow at [email protected].