Katrina and Rita struck the heart of the GoM’s oil and gas production on August 29 and September 25 respectively, but energy experts have recently predicted the flow of petroleum would not be fully restored until after midway through next year.

These two hurricanes ploughed through 3,050 of the 4,000 drilling platforms in the GoM, destroying 108 mostly older structures and severely damaging 53 platforms. But more modern equipment escaped relatively unscathed, with only one major platform seriously damaged, according to a recent US Minerals Management Service report.

As of last week, nearly 414,500 barrels, or 28%, of GoM oil production remained offline, while 20% or over 2 billion cubic feet of natural gas production is still shut-down, the agency said.

In addition, US refineries were still struggling to make a full comeback, with about 804,000 barrels of petrol production still offline. Two refineries are still shut, two more are operating at a slower rate, and one is expected to reach full production next week. Meanwhile, repairs continue to pipelines and processing plants.

After the hurricanes hit, US lawmakers started considering ways to expand offshore production of oil and natural gas and to encourage construction of new refineries away from the Gulf Coast.

In the petroleum industry it was the giants that suffered most from the twin storms. Insurance agencies say the hurricanes struck while some companies were still trying to get claims settled from Hurricane Ivan, which damaged GoM oil operations in September last year.

In October, BP, the world’s second largest oil company by market capitalisation, said the storms cost it more than US$700 million in lost production and was likely to stop the company achieving its 2005 output target.

Rita and Katrina cost BP an average of 145,000 barrels of oil equivalent per day (boepd) in lost production during the September quarter, with third quarter oil and gas output of only 3.8 million boepd. This compares with 4.1 milllion boepd during the second quarter and 3.9 million boepd a year ago.

BP shut its flagship US refinery in Texas City, as well as two other plants before the two hurricanes struck.

Meanwhile, repairs are continuing at Shell Oil’s Mars platform, damaged by Katrina. Mars was the hardest-hit of the company’s four gulf platforms and one that accounted for 20% of its GoM production.

Shell this week said it expected to resume production from the platform in the latter half of next year. Currently, Shell is operating at less than half its production capacity, or at 200,000 barrels per day down from 450,000 bopd before the storms.

Another major still reeling from Rita is BHP Billiton, which warned in October that production from the Typhoon-Boris fields would not return to normal production for months. The company also expected to lose about 4.5 million barrels of oil equivalent from its GoM operations this fiscal year.

BHP’s facility most damaged by Rita was its US$256 million Typhoon tension leg oil platform moored about 165km from New Orleans, which suffered severe damage after being cut from its mooring. The production platform had been producing 400,000 barrels of oil and 60 million cubic feet of gas per day.

In the current financial year, production through Typhoon was expected to account for almost 5% of BHP’s total oil and gas production.

But it wasn’t only the giants that felt the full-force of this Atlantic hurricane season. The loss of production and shutdown of refineries created a panic on the markets and a fuel shortage across the US, which derives 20% of its petroleum production from the GoM.

In the aftermath of Hurricane Katrina, world oil prices reached record highs of over US$70 per barrel. High prices continued, but eased slightly to about US$64 per barrel the following week.

Before the markets could settle in the wake of Katrina, the news Rita was on her way renewed jitters, sending crude oil futures surging more than US$4 on September 20 – the biggest one-day hike on record.

Once again, personnel were evacuated and more offshore oil and gas platforms and rigs were shut-down in the GoM.

Rita eased to a Category 4 storm as it approached Texas, but still managed to set records, after damaging more oil rigs than any other storm in history. Nine semi-submersible rigs had broken from their moorings and were adrift, including BHP’s Typhoon leg. At the time, ODS Petrodata said this would lead to a shortage of rigs in the GoM and major drilling delays for companies in the US and around the world.

It said while Katrina was a more powerful storm than Rita, it moved through mature areas of the US Gulf containing mostly oil production platforms, while Rita hit the western gulf, where there was a lot of exploratory drilling.

But the markets reacted less strongly to Rita’s arrival, as Katrina’s devastation within the month had already caused US crude demand to tumble by nearly 30%. On September 23, over 91% of the GoM’s production facillities were closed.

Combined, Katrina and Rita caused at least 595 petroleum and chemical spills across four US states, releasing 39.5 million litres of oil, comparable with the 48.5 million litres released by the Exxon Valdez oil tanker in Alaska in 1989.

The storms also released other chemicals, and the oil spills they caused were not contained in one area but were spread across a region, occurring in difficult-to-reach wilderness areas, rural countryside and residential neighbourhoods.

The collective impact of Katrina and Rita has been ranked as one of the worst environmental disasters in US history, and weather experts warn there is more yet to come.

Climatologists claim elevated levels of global warming are probably contributing to an increase in hurricane ferocity. Analysts measuring ocean temperatures and trade winds – the two big factors that breed severe storms in the Caribbean and North Atlantic – say 2005 is on track to be the worst-ever year for hurricanes.

In addition, 2003 and 2004 have the highest two-year totals of hurricane activity ever seen in the North Atlantic, with climatologists from London-based Tropical Storm Risk saying this coincides with rises in termperature caused by global warming.

Hurricanes form from thunderstorms over tropical waters that are warmer than 27.2 C, with the temperature difference between the sea surface and air above the storm the primary factor in storm strength.

In new research from the Georgia Institute of Technology, Atlanta, experts say the number of high-intensity cyclones has doubled since the 1970s.

This is bad news for the oil and gas industry, which is now considering revising its storm standards for platform criteria.

Comparisons were inevitably drawn between Hurricane Ivan and Katrina, both Category 5 storms at the time they bore down on the GoM.

At the time, Ivan was considered one of the strongest storms on record.

Around the world, offshore platforms are generally built to survive a so-called 100 year storm – a hurricane so strong that it typically occurs once every 100 years.

But most definitions of a 100-year event were calculated before it received two of them – Ivan and Katrina – in less than 12 months.