About 30% of the world's oil comes from beneath the sea — from jackup rigs in the shallow Persian Gulf to drillships working two miles of water off Brazil and Guyana. How the engineering works, what it costs, and what Deepwater Horizon changed.
| Hardware | Water depth | Role |
|---|---|---|
| Jackup rig | to ≈120 m | Legs on the seabed; the shallow-water workhorse (Persian Gulf, SE Asia) |
| Semi-submersible | to ≈3,000 m | Floating, ballasted for stability; drilling and some production |
| Drillship | to ≈3,600 m | GPS-thruster station-keeping; the deepwater exploration standard |
| Fixed platform | to ≈500 m | Steel/concrete production hubs (North Sea, Gulf shelf) |
| FPSO | any | Floating production/storage ship — the deepwater production standard (Brazil, Guyana, West Africa) |
| Subsea systems | any | Wellheads on the seabed, tied back miles to hosts — no surface structure at all |
Where it happens: US Gulf of Mexico · Atlantic Canada · Brazil\'s pre-salt (see biggest fields). The risk history: biggest oil spills.
Shallow water (to ~120 m) uses jackup rigs standing on the seabed. Deepwater uses floating drillships or semi-submersibles holding position with GPS thrusters, drilling through kilometers of water then kilometers of rock. Production then flows to fixed platforms, subsea systems, or FPSOs — ship-shaped floating factories that process and store oil for shuttle tankers.
Wells are now drilled in over 3,000 meters (10,000 feet) of water — and total depths (water plus rock) beyond 10 km. Brazil's pre-salt fields produce through 2 km of water and 5 km of rock including a salt layer; each such well can cost $100–200 million.
Roughly 30%. The heavyweights are the Middle East's shallow Gulf fields (Safaniya, Zakum), Brazil's pre-salt, the US Gulf of Mexico (~1.8 Mb/d), the North Sea, West Africa — and the newest star, Guyana, which went from zero to ~650,000 b/d in five years on ExxonMobil's Stabroek block.
Yes — the survivors got lean. Deepwater projects sanctioned today typically break even at $25–45/bbl, competitive with shale, and once built they produce for decades with low decline. The catch is the up-front bet: $5–10+ billion committed 5–7 years before first oil, which is why deepwater investment collapses in every price bust.
The 2010 Macondo blowout (11 deaths, ~210 million gallons) produced a US drilling moratorium, a new safety regulator (BSEE), well-design and blowout-preventer rules, and an industry-funded containment fleet on permanent standby. Deepwater safety margins improved materially — though the fundamental risk of high-pressure wells far from shore can be managed, not eliminated.