Offshore Giants: The World’s Deepest Wells & Biggest Platforms

When the first offshore well was drilled off the coast of Summerland, California, in 1896, few could have imagined just how far the industry would go. That wooden pier-mounted rig stood just a few feet above the water, using the same cable-tool method employed on land. Its operators ventured only a short distance from shore to tap into shallow reservoirs.

Now, more than a century later, offshore oil and gas operations have pushed to extremes that early drillers would have considered impossible. Some of today’s wells extend more than 40,000 feet below the seabed, drilled in water depths exceeding 12,000 feet. Platforms have transformed from modest wooden structures to towering engineering marvels—some heavier than skyscrapers, standing hundreds of feet above the sea, and capable of producing over 200,000 barrels of oil a day. Floating facilities like the Prelude FLNG, nearly 1,600 feet long, house hundreds of workers and process gas directly at sea.

These achievements are more than records. They represent the technical ingenuity of working at the edge of what’s possible. Here, we’ll take a closer look at the deepest offshore wells ever drilled and the largest rigs and platforms in the world, offering a glimpse into the scale and ambition of the offshore oil and gas industry.

The World’s Deepest Wells

Extracting oil and gas has always been a race against depth. The easiest reservoirs were tapped decades ago, forcing operators to drill farther offshore and deeper beneath the seafloor to reach untapped reserves. 

With every year that passes, rigs drill deeper—chasing energy at the ocean’s depths.

Al Shaheen BD-04A (Qatar)

Total Depth: ~40,320 ft (12,290 m)

In 2008, the BD-04A well was drilled in the Al Shaheen field offshore Qatar, setting a record at the time for one of the longest extended-reach offshore wells ever drilled. The 35,770-foot horizontal section of the well was placed in a reservoir only 20 feet thick, as part of an effort to tap thin, widely dispersed oil reservoirs beneath thick layers of rock.

Odoptu OP-11 (Sakhalin, Russia)

Total Depth: 40,502 ft (12,345 m)

In 2011, this extended-reach drilling project surpassed the previous record held by Al Shaheen BD-04A, setting the benchmark for how far offshore operators can extend wells from onshore platforms into offshore reservoirs—especially in challenging subarctic conditions. The well also set a record for horizontal reach, at 37,648 feet.

Z-44 Chayvo (Sakhalin, Russia)

Total Depth: ~40,602 ft (12,376 m)

The Z-44 Chayvo well, drilled in 2012, broke the record set by Odoptu OP-11 in 2011 and is often cited as the world’s deepest extended-reach well. Located off Sakhalin Island in the Sea of Okhotsk, the well required precision drilling through harsh, icy conditions. Its massive reach has allowed operators to tap reservoirs far from the surface location without constructing additional offshore platforms. 

Tiber (Gulf of Mexico, USA)

Vertical Depth: ~35,050 ft (10,683 m)

Before the 2010 blowout disaster that made the name infamous, the Deepwater Horizon rig drilled the Tiber exploration well in 2009, breaking records for vertical depth. Located in about 4,132 feet of water, the Tiber well confirmed the potential of ultra-deep reservoirs in the Gulf (estimated to contain 4 to 6 billion barrels of oil), though development has been limited due to its extreme pressures and challenging geology. 

Ondjaba 1 (Angola)

Water Depth: ~11,903 ft (3,628 m)

In 2021, the Ondjaba 1 exploration well set a new world record for water depth when it was drilled in Block 48 offshore Angola. Operating at nearly 12,000 feet of water, the well showcased the capabilities of ultra-deepwater drillships, which use dynamic positioning systems instead of fixed moorings—allowing drilling beyond the continental shelf.  

The World’s Biggest Platforms & Rigs

Offshore platforms have grown from wooden structures perched on shallow pilings to towering engineering marvels. Today’s largest rigs are not just oil and gas production facilities—they are floating cities, housing dozens or hundreds of workers, processing millions of barrels of hydrocarbons, and withstanding some of the harshest conditions on Earth. Some weigh hundreds of thousands of metric tons, stand taller than the Eiffel Tower, and are designed to survive hurricane-force winds, iceberg strikes, and Arctic ice sheets.

Prelude FLNG (Australia)

Length: 1,601 feet (488 m)

Weight: ~600,000 metric tons (fully loaded)

Commissioned in 2018, Prelude FLNG (floating liquefied natural gas platform) is the largest floating offshore facility ever built. It extracts, processes, and liquifies gas directly at sea, allowing production from remote offshore fields that would otherwise be too expensive to develop. Prelude also accommodates around 200 workers, making it a true floating city.

Hibernia Platform (Canada)

Height: 735 ft (224 m)

Weight: ~1.2 million metric tons (with ballast)

Located off Newfoundland and Labrador, the Hibernia Platform was designed to survive direct iceberg strikes in the North Atlantic. Its massive concrete gravity-based structure can store 1.3 million barrels of crude, and its topside production facilities have been kept in operation since 1997. 

Troll A Platform (Norway, North Sea)

Height: 1,549 ft (472 m)

Weight: ~1.2 million metric tons (with ballast)

The Troll A platform is the tallest structure ever moved by humans. Installed in 1996, its steel-reinforced concrete legs extend more than 300 meters (984 feet) below the surface, anchoring it to the North Sea floor. It takes nine minutes by elevator to travel from the sea floor to the platform. Troll A produces massive amounts of natural gas for Europe and remains an engineering icon decades after its installation. 

Gullfaks C (Norway, North Sea)

Height: 1,247 ft (380 m)

Weight: ~420,000 metric tons

Installed in 1989, Gullfaks C is the oldest platform on our list. It is also one of the heaviest offshore platforms ever built and holds the Guinness World Record for the heaviest manmade object ever moved. Its gravity-based structure supports drilling and oil production in the harsh North Sea. Gullfaks C has a crude oil storage capacity of 2 million barrels and can accommodate a crew of about 300.

Petronius Platform (Gulf of Mexico, U.S.)

Height: 2,100 ft (640 m)

Weight: ~43,000 metric tons

Installed in 2000, Petronius is one of the tallest structures in the world. Its compliant-tower design allows it to flex with strong ocean currents, making it ideal for deepwater operations in hurricane-prone areas of the Gulf of Mexico. It is located about 130 miles southeast of New Orleans, Louisiana, where the water depth is 1,754 feet.

Thunder Horse PDQ (Gulf of Mexico, U.S.)

Height: ~433 ft (132 m)

Weight: ~130,000 metric tons

Commissioned in 2008, Thunder Horse PDQ (production-drilling-quarters) is the largest semisubmersible production and drilling platform in the world. It was designed to endure Category 5 hurricanes and operates in approximately 6,040 feet of water about 150 miles off the coast of New Orleans. It typically houses a crew of about 200.

Perdido Spar (Gulf of Mexico, U.S.)

Height: ~555 ft (169 m)

Weight: ~20,956 metric tons

The Perdido holds the record as the world’s deepest spar platform. The floating drilling and production platform is designed for use in deepwater and ultra-deepwater environments, anchored to the seabed by a large, cylindrical hull. Installed in 2010, it operates in 8,000 feet of water about 200 miles south of Galveston, Texas, and was designed for stability in the harsh Gulf environment. 

Olympus TLP (Gulf of Mexico, U.S.)

Height: ~400 ft (123 m)

Weight: ~120,000 metric tons

Brought online in 2014, Olympus was designed to access deeper reservoirs in the Mars B development and is expected to extend the field’s life to at least 2050. The tension-leg platform operates in 3,100 feet of water about 130 miles south of New Orleans, Louisiana. Construction of the massive platform involved more than 25,000 personnel.

Berkut Platform (Sea of Okhotsk, Russia)

Height: ~472 ft (144 m)

Weight: ~200,000 metric tons

Production Capacity: ~45,000 barrels of oil per day

Built for the extreme subarctic and fixed to the seabed, Berkut features an ice-resistant design capable of withstanding heavy seas (including 60-foot waves) and extreme cold (temperatures as low as -47 degrees Fahrenheit). It remains one of the largest Arctic oil platforms in operation. 

Pushing the Limits of Offshore Engineering

From the record-breaking depths of the Z-44 Chayvo well to the towering mass of platforms like Troll A and Petronius, the offshore oil and gas industry continues to push the boundaries of possibility. These engineering feats demonstrate remarkable innovation, but with greater scale and deeper drilling comes greater risk. 

Ultra-deepwater wells are subjected to extreme pressures and temperatures, and massive platforms must endure decades of harsh marine conditions. The challenge will be ensuring that safety keeps pace with these advancements. The deeper the wells and the bigger the rigs, the more complex the operations—and the bigger the fallout if something goes wrong.

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Arnold & Itkin has represented offshore workers and their families in some of the most significant cases in maritime history. From catastrophic platform accidents to ultra-deepwater rig disasters, the firm has fought to hold companies accountable when they put profits over safety. With more than $20 billion won for clients, Arnold & Itkin continues to stand up for the men and women who work in one of the world’s most dangerous industries—making sure their rights are protected.