To Store Oil and Hazardous Cargo, South Korea Built Underground Industrial Caverns Capable of Holding 146 Million Barrels, Connected to Ports and Refineries by Tunnels in Ulsan

Written by Débora Araújo

Published on 13/01/2026 at 17:41

Para armazenar petróleo e cargas perigosas, a Coreia do Sul construiu cavernas industriais subterrâneas capazes de guardar 146 milhões de barris, conectadas a portos e refinarias por túneis em Ulsan

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South Korea Uses Industrial Underground Caverns to Store 146 Million Barrels of Oil and Hazardous Cargoes Linked to Ports and Refineries in Ulsan.

According to documents from the Korea National Oil Corporation (KNOC), responsible for the country’s energy strategy, the system of underground industrial caverns for the storage of oil and hazardous cargoes began construction in the early 1980s, during South Korea’s logistical restructuring. The goal was threefold: to increase national strategic reserves, protect flammable substances, and free up limited urban and port space for industry and housing.

The first phase began operating in 1986, and since then new caverns and corridors have been excavated, increasing the total capacity to approximately 146 million barrels of crude oil, derivatives, and liquefied petroleum gas (LPG). For comparison, this volume would be equivalent to more than 7 months of domestic consumption in Korea in the 1980s or more than two fully loaded VLCC supertankers.

Why Store Oil Inside a Mountain?

Unlike other countries such as the United States and China, which store oil in deep saline caverns or aboveground tanks, South Korea has favorable geology for caverns excavated in crystalline rock, especially in the Ulsan region.

ARTICLE CONTINUES BELOW

Caverns Excavated with Mining Engineering and Port Infrastructure

The heart of the system is the set of caverns housing oil in giant underground chambers, some over 100 meters long and dozens of meters wide, all connected by access tunnels, technical corridors, and industrial pipelines. These caverns are not makeshift deposits but planned structures following mining engineering standards:

Internal Lining to prevent infiltrations
Pressure and Ventilation Control
Segregated Piping System
Gas, Temperature, and Humidity Sensors
Valve and Pump Rooms

The proximity to the sea allows tankers to load and unload directly using submarine pipelines that reach the underground terminal. On the other side, the land connection takes oil to the refineries in Ulsan, Onsan, and Yeosu, consolidating a petrochemical corridor integrated on a continental scale.

One of the Largest Underground Strategic Reserves on the Planet

The number of 146 million barrels is not arbitrary. It is part of a national strategy that has caught the attention of allied and rival countries. Of the total:

one part is national stock, for supply emergencies
another part is commercial stock, leased to buyers such as Japan, the U.S., and IEA members
and the remainder serves for petrochemical transit, supplying refineries and exports

This hybrid arrangement has transformed Ulsan into an energy hub: oil arrives, is stored, refined, and re-exported. All of this beneath a solid layer of rock, invisible to those passing through the city.

Hazardous Cargoes and the Urban Density Issue

With the growth of Korean cities and the advancement of industrialization from the 1970s onwards, a dilemma emerged: where to place highly hazardous facilities when the country is small, densely populated, and has limited coastal area? Under the cities, Korea found the answer. In addition to Ulsan, the country has built:

Underground LPG Stations
Pressurized Depots
Shielded Chemical Warehouses

All to reduce urban risks and industrial accidents in densely populated areas. According to KNOC itself, this type of underground infrastructure drastically reduces the risk of urban fires and eliminates the need for exclusion zones above ground.

Geopolitics and Energy: A Country Without Oil Became a Petrochemical Power

South Korea has no oil and depends almost 100% on imports. Nevertheless, it has become one of the world’s largest producers of:

Petrochemical Resins
Marine Fuels
Industrial Fertilizers
Technical Polymers

How? With integrated logistics, giant refineries, and underground terminals like those in Ulsan. Today, the country is home to giants such as:

SK Energy
Hyundai Oilbank
S-OIL
LG Chem

The result is a fascinating paradox: a country without oil supplying the world with petrochemicals. The underground terminals are a key piece of this puzzle.

Why Almost No One Knows About This Type of Infrastructure?

There are three main reasons:

It’s Underground There are no “pretty pictures” like offshore platforms or illuminated refineries.
It Was Not Designed to Be Touristic Its function is technical, defensive, and industrial.
The World Focuses on Oil in the Middle East, Not Korea

While the global focus is on Saudi Arabia, Iraq, and Iran, few realize that Korea has built a quiet model of energy security.

From Underground to the Future of Energy

With the energy transition underway, structures like the caverns in Ulsan may gain new uses. South Korean experts are already studying the possibility of converting hydrocarbon caverns into:

Hydrogen Depositories
Compressed Air Reservoirs
Strategic CO₂ Storage

In other words, what began for oil can turn into infrastructure for decarbonization. This places the country at the table for the next decade: the underground as a logistical asset.

To Store Oil and Hazardous Cargo, South Korea Built Underground Industrial Caverns Capable of Holding 146 Million Barrels, Connected to Ports and Refineries by Tunnels in Ulsan

South Korea Uses Industrial Underground Caverns to Store 146 Million Barrels of Oil and Hazardous Cargoes Linked to Ports and Refineries in Ulsan.

Why Store Oil Inside a Mountain?

Caverns Excavated with Mining Engineering and Port Infrastructure

One of the Largest Underground Strategic Reserves on the Planet

Hazardous Cargoes and the Urban Density Issue

Geopolitics and Energy: A Country Without Oil Became a Petrochemical Power

Why Almost No One Knows About This Type of Infrastructure?

From Underground to the Future of Energy

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To Store Oil and Hazardous Cargo, South Korea Built Underground Industrial Caverns Capable of Holding 146 Million Barrels, Connected to Ports and Refineries by Tunnels in Ulsan

South Korea Uses Industrial Underground Caverns to Store 146 Million Barrels of Oil and Hazardous Cargoes Linked to Ports and Refineries in Ulsan.

Why Store Oil Inside a Mountain?

Caverns Excavated with Mining Engineering and Port Infrastructure

One of the Largest Underground Strategic Reserves on the Planet

Hazardous Cargoes and the Urban Density Issue

Geopolitics and Energy: A Country Without Oil Became a Petrochemical Power

Why Almost No One Knows About This Type of Infrastructure?

From Underground to the Future of Energy

With billions in loans, China is rebuilding Nigeria’s railway network from scratch, abandoning the British colonial tracks that have turned to scrap and creating a corridor of over 1,300 km to take the load off the roads of Africa’s largest economy.

Forget petroleum-based asphalt: a Scottish company transforms 684,000 plastic bottles into one kilometer of road that is 60% more resistant and up to 10 times more durable, and the technology has already started replacing traditional asphalt in more than 30 countries.

Austrian engineers have developed an inflatable concrete technology that transforms flat slabs into domes using only air pressure, eliminating scaffolding and temporary forms, and potentially changing the way bridges, tunnels, and curved roofs are constructed worldwide.

Australia prepares to dredge 96.5 million m³ in Moreton Bay to deepen, widen, and realign channels of the Port of Brisbane, in a project of up to 25 years designed to accommodate larger ships and enhance maritime safety and regional port efficiency.

A robot named Walter does the work of five bricklayers per hour and can save the construction industry, where the average age of professionals is 46 years and almost no one wants to learn the trade anymore, in the United Kingdom.

Spain installs two giant pipelines 2.2 km off the coast to draw water from the Mediterranean and supply a megafacility capable of producing 200 million liters of drinking water per day.

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The sea has stopped just warming and has started pushing storms towards the continent: marine heatwaves are already entering the path of up to 25% of extreme coastal rains and can increase storms by 30%, worsening floods on the coast.

While traditional constructions rely on tons of concrete to support weight, in England an abandoned site was converted into transparent hexagonal domes, combining lightweight engineering and mine repurposing, transforming the landscape and local tourism.

The bridge that collapsed in seconds after being hit by a ship in Baltimore will be reborn as a cable-stayed bridge: Maryland signed $4.8 billion in four contracts for a 508-meter span specifically designed to withstand the impact of a giant cargo ship.