Floating production storage and offloading

Based on Wikipedia: Floating production storage and offloading

Imagine a ship so massive it makes aircraft carriers look modest—nearly half a kilometer long, wider than a football field, and carrying enough equipment to process the raw output of an entire oil field. Now imagine that this floating industrial complex can simply pick up and sail away when the oil runs dry, ready to start again somewhere else on the planet. This is the world of floating production, storage, and offloading vessels, better known by their acronym FPSO (pronounced "eff-pee-ess-oh").

These remarkable vessels represent one of humanity's most audacious engineering solutions to a fundamental problem: how do you extract oil and gas from beneath thousands of meters of ocean, in locations so remote that building permanent infrastructure would be economically absurd?

The Problem with Pipelines

To understand why FPSOs exist, you first need to understand why the alternative—subsea pipelines—often doesn't work.

When oil was first extracted from offshore locations in the late 1940s, the solution was simple: build a platform that sits on the seabed, drill down, and pipe the oil back to shore. This works beautifully in shallow waters close to land. The North Sea, the Gulf of Mexico's continental shelf, and countless other locations have been developed this way, with networks of pipelines crisscrossing the seafloor like underground highways.

But as the easy oil disappeared, exploration pushed into deeper waters and more distant locations. By the 1970s, companies were drilling in places where the economics of pipelines simply collapsed. Consider an oil field two hundred kilometers offshore in water over a kilometer deep. A pipeline to shore might cost hundreds of millions of dollars and take years to build. If the field only contains enough oil for five or six years of production, that pipeline becomes an extravagantly expensive straw.

The solution? Bring the entire processing facility to the oil, rather than bringing the oil to the facility.

A Factory That Floats

An FPSO is, at its core, a complete oil and gas processing plant mounted on a ship's hull. Raw hydrocarbons flow up from wells on the seafloor through flexible pipes called risers. Once aboard, the crude goes through the same separation and treatment processes it would undergo at any land-based facility: gas is separated from oil, water is removed, and the resulting products are prepared for market.

But here's where the "S" in FPSO becomes crucial. Unlike a land-based refinery that can pump its output directly into a pipeline network, an FPSO must store everything it produces until a tanker arrives to take it away. These vessels carry enormous storage tanks in their hulls—some holding over two million barrels of oil. That's enough to fill roughly 130 Olympic swimming pools.

When a shuttle tanker pulls alongside (or more often, behind) the FPSO, the stored oil is "offloaded"—pumped from the FPSO's tanks into the tanker over a period of hours. The tanker then sails to a refinery, while the FPSO continues producing and storing, waiting for the next pickup.

Variations on the Theme

The basic FPSO concept has spawned several related vessel types, each optimized for different purposes.

The simplest variant is the Floating Storage and Offloading unit, or FSO. This is essentially an FPSO without the processing equipment—just a giant floating tank. FSOs typically receive already-processed oil from nearby platforms and hold it until tankers arrive. Many FSOs are converted from old supertankers that have reached the end of their useful life as cargo vessels but still have perfectly good hulls for stationary storage.

The most famous FSO was the Knock Nevis, which for decades held the record as the largest ship ever built. Originally constructed in 1979 as a supertanker called the Seawise Giant, this behemoth stretched 458 meters—so long that the crew used bicycles to get around on deck. After being bombed and sunk during the Iran-Iraq War, then refloated and repaired, the vessel eventually found new life as a floating storage unit in Qatar's Al Shaheen oil field before being scrapped in 2010.

At the other end of complexity sits the Floating Drilling Production Storage and Offloading vessel, or FDPSO. These add drilling capability to the standard FPSO package, allowing a single vessel to explore for oil, drill the wells, process the output, and store it for export—an entire offshore operation in one hull.

Then there's the increasingly important Floating Storage and Regasification Unit, or FSRU. These vessels handle liquefied natural gas, or LNG—natural gas that has been cooled to minus 162 degrees Celsius until it condenses into a liquid occupying just one six-hundredth of its gaseous volume. FSRUs receive LNG from specialized carrier ships, warm it back into gas, and send it ashore through pipelines. As of 2022, thirty-three FSRUs were operating worldwide, and they've become strategically vital as countries seek alternatives to pipeline gas from politically problematic suppliers.

Engineering for the Unforgiving Sea

Building a floating factory that must operate continuously for decades in the open ocean presents engineering challenges that would give most designers nightmares.

Consider the mooring problem. An FPSO must stay precisely positioned over its wells, connected by risers that can flex but not stretch indefinitely. In shallow waters, this might mean anchoring to the seabed with chains and cables. But in deep water—say, 2,600 meters, nearly two miles down—the weight of conventional mooring lines would be prohibitive.

The FPSO BW Pioneer, operating for Petrobras in the Gulf of Mexico's Walker Ridge block, solved this problem with a disconnectable turret system. The vessel rotates around a central mooring point like a weathervane, always pointing into the wind and waves to minimize stress. And when a hurricane approaches—a regular occurrence in the Gulf of Mexico—the BW Pioneer can physically disconnect from its turret, sail away to safety, then return and reconnect when the storm passes.

This ability to disconnect represents a crucial advantage over fixed platforms. When Hurricane Katrina devastated the Gulf of Mexico in 2005, it destroyed or severely damaged over a hundred offshore platforms. FPSOs with disconnect capability simply weren't there when the storm arrived.

The Largest Moving Objects Ever Built

The scale of modern FPSOs defies easy comprehension.

The Kizomba A, operated by ExxonMobil offshore Angola, weighs 81,000 tonnes and stores 2.2 million barrels of oil. Stretched out, it would cover most of three football fields laid end to end. Building it at Hyundai Heavy Industries in South Korea cost over 800 million dollars.

But the Kizomba A looks almost modest compared to Shell's Prelude facility, which began operations in 2018 off the coast of Western Australia. At 488 meters long and 74 meters wide, Prelude is the largest floating structure ever built—longer than the Empire State Building is tall. It processes natural gas into LNG, stores it, and loads it directly onto carrier ships, eliminating the need for any onshore infrastructure in a remote corner of the Australian coast.

Prelude cost approximately twelve billion dollars to build. That eye-watering figure reflects both the vessel's unprecedented scale and the complexity of liquefying natural gas at sea—a process that requires cooling gas to cryogenic temperatures while the entire facility bobs in ocean swells.

The Economics of Mobility

The ability to relocate is perhaps the FPSO's most underappreciated advantage.

A conventional offshore platform is a permanent installation. When its field runs dry, the platform becomes an expensive piece of scrap metal that must be laboriously decommissioned—dismantled piece by piece at costs that can run into hundreds of millions of dollars. The owner gets nothing back.

An FPSO, by contrast, sails away. The same vessel that produced oil offshore Brazil for fifteen years might spend its next decade offshore West Africa, then move to Southeast Asia. The initial investment—which can approach a billion dollars for a new-build vessel—gets amortized across multiple fields over a working life that can exceed forty years.

This mobility has transformed how oil companies think about marginal fields. Deposits that hold perhaps fifty million barrels—not worth building permanent infrastructure for—become economically attractive when a leased FPSO can arrive, produce for five years, and leave. The breakeven size for offshore developments has dropped dramatically.

The flip side is a flourishing market in converted tankers. Rather than building a billion-dollar vessel from scratch, operators can convert existing oil tankers into FPSOs for under a hundred million dollars. The conversion replaces cargo-handling equipment with processing systems while keeping the hull, engines, and accommodation spaces largely intact. This approach makes sense for smaller fields where a purpose-built vessel would be overkill.

The Norwegian Marvel

Not all FPSOs are created equal, and the Skarv FPSO demonstrates just how sophisticated these vessels have become.

Operating in the Norwegian Sea for BP, Skarv processes both oil and natural gas from multiple subsea wells—five separate templates feeding into a single floating facility, with capacity to add more in the future. The processing plant aboard handles nearly 670 million cubic feet of gas and half a million barrels of oil equivalent per day.

What makes Skarv particularly interesting is how it handles its output. The oil stays aboard until tankers arrive, but the gas travels eighty kilometers through a subsea pipeline to join the Åsgard transport system—a major European gas artery. The vessel thus operates as both a traditional FPSO (storing and offloading oil) and as a conventional offshore platform (exporting gas by pipeline).

Skarv's hull, built by Samsung Heavy Industries in South Korea, incorporates a proprietary design called Tentech975 that optimizes stability and fatigue resistance for the harsh conditions of the Norwegian Sea. The vessel accommodates about a hundred workers in single-occupancy cabins—a level of comfort that reflects Norway's strong union culture and high labor standards.

A Global Fleet

Today, over 270 FPSOs operate worldwide, and the fleet continues to grow. They work in virtually every offshore oil-producing region: the Gulf of Mexico, the North Sea, offshore Brazil, the waters of West Africa, Southeast Asia, and Australia.

The industry has developed its own ecosystem. Specialized companies like SBM Offshore, BW Offshore, and MODEC build, own, and operate FPSOs that oil companies lease rather than purchase. Shipyards in South Korea, Singapore, and China compete for construction contracts. Classification societies certify that vessels meet safety standards. Insurance markets have learned to price the unique risks of floating production.

The first FPSO, commissioned by Shell in 1977 for the Castellon field in Spain's Mediterranean waters, seems almost quaint by comparison—a proof of concept that demonstrated floating production could work. In the five decades since, the technology has evolved from experimental to essential, enabling oil production in waters so deep and locations so remote that they would otherwise remain forever out of reach.

The Future Floats

As the world's appetite for energy continues—and as the energy transition creates new demands for natural gas as a bridge fuel—FPSOs and their LNG-handling cousins seem certain to proliferate.

The FSRU market has grown particularly rapidly. Countries that want access to global LNG supplies but lack the demand to justify building permanent import terminals find FSRUs an attractive alternative. A floating terminal can be leased, positioned, and operating within months rather than the years required for land-based construction. It can also be moved if circumstances change—a flexibility that proved valuable when FSRUs relocated to higher-priced markets during the 2022 European energy crisis.

Meanwhile, the boundaries of what's possible continue to expand. Shell's Stones project in the Gulf of Mexico, which began production in 2016, operates in water depths of nearly 2,900 meters—approaching two miles. The reservoir itself lies another 8,000 meters below the seafloor. Producing oil from such depths would have seemed like science fiction to the engineers who built the first offshore platforms in the shallow waters of Louisiana seventy-five years ago.

These floating production vessels represent something profound about human ingenuity: when the economics demand it, we find ways to build factories in places factories were never meant to exist. Cities float on barges in Amsterdam's harbor. Server farms hum inside converted shipping containers. And out in the deep ocean, structures larger than the largest ships process petroleum from deposits miles beneath the waves, then pack up and sail away when the job is done.