Despite an almost universal recognition of the need to find alternatives to fossil fuel, the world’s insatiable demand for oil and gas continues to gain pace, driving oil companies to search fresh reserves under ever more challenging conditions. The Thunder Horse Platform in the Gulf of Mexico is an astonishing example of how this challenge has stimulated engineers to build increasingly massive and sophisticated structures.
The oil field, discovered 240 kilometers south of the Louisiana coast by BP in 1999, is the largest ever found in this region, but tapping into this rich reservoir poses problems that can scarcely be imagined. The oil lies buried under 6,000 metres of rock and mud beneath the sea 1,830 metres deep. When drilled for such a depth, oil emerges at a pressure of 17,400 psi and at a temperature of 135 degrees Celsius-conditions never previously encountered on any offshore rig. It was these extreme demands that led to innovative floating oil platform in the world.
With a deck size of three soccer field, the platform is essentially a giant raft that floats on submerged watertight pontoons.The main structure, supported on four corner columns, is a rectangular steel box measuring 136 metres long, 111 meters wide, and 10 metres high. It contains living quarters for a workforce of 139, while operational equipment is housed in modules alongside the helipad and drilling derrick on the open deck. Licked into a network of submarine pipelines, Thunder Horse is designed to produce up to 250,000 barrels of oil and 5.6 million cubic metres of natural gas a day, but, unlike most offshore rigs, it incorporates a range of innovative features designed to minimize environmental harm. Sand is bought up to the surface by pumps, then shipped to shore for cleaning and recycling, while waste water, instead of being flushed into the ocean, is mixed with seawater and then injected back into the oilfield to maintain the reservoir’s high pressure.
BP discovered this oilfield by sending the drill-ship Discovery 534 to sink a “discovery well” in 1999. Enough oil was found to have the drill-ship Discoverer Enterprise send down an appraisal well. Discoverer 534 then found more oil further north, BP started building the production platform. Despite risks that the oil estimated were wrong or the oil prices were collapse, the potential profit is enormous. Thunder Horse is expected to hand at least 1 billion barrels of oil over next 25 years and, after Hurricane Katrina struck in 2005, prices rocketed, making Thunder Horse’s “black gold” worth $70 billion on that day.
Thunder Horse PDQ was evacuated with the approach of Hurricane Dennis in July 2005. After the hurricane passed, the platform fell into a 20 degree list and was in danger of foundering. The platform was designed for a 100-year event, and inspection teams found no hull damage and no leaks through its hull.
- Designing and building the platform took 15 million man hours.
- Thunder Horse displaces 143,000 tons of seawater.
- The platforms impact on the environment is lowered as it recovers waste heat, reducing the energy bill.