China’s CNOOC Strikes Ultra-Deep Gas 5,770 Metres Down in the Bohai Sea — What the Discovery Means

China’s biggest offshore oil and gas company has drilled one of the deepest gas wells in its history — and found a strong flow of natural gas buried in volcanic rock nearly six kilometres below the sea. The discovery, announced on Thursday, 12 November 2026, could open up a whole new area for gas exploration in northern China, although the company has not yet said how much gas can actually be recovered or when it might start producing.

China National Offshore Oil Corporation, known as CNOOC, said its new well in the central Bohai Sea reached a total depth of 5,770 metres — about 3.6 miles, or roughly 19,000 feet — and flowed about 800,000 cubic metres of natural gas a day during testing. That is the same as about 28 million cubic feet a day. The company called the find a major breakthrough in offshore ultra-deep gas exploration.

The well was drilled near the Bozhong Sag, the largest area of oil- and gas-bearing rock in the Bohai Sea. On its way down, it passed through more than 120 metres of gas-bearing layers hidden inside volcanic rock — a type of rock that is very hard to explore, because it does not behave like the sandstone and limestone where gas is usually found.

What exactly did CNOOC find?

In simple terms, CNOOC drilled a very deep hole in the seabed, hit gas, and measured how fast the gas flowed out. Three numbers tell the story.

First, the depth. The well was completed at 5,770 metres below the surface, in a formation deeper than 5,000 metres. Wells this deep are called ultra-deep, and they are among the hardest and most expensive to drill. At those depths, the rock is under huge pressure and the temperature can be extremely high — in nearby wells in the same area, reservoir temperatures have reached 204 degrees Celsius, hot enough to boil water many times over.

Second, the rock. The gas was found in volcanic formations — rock formed from ancient lava, not the layered sedimentary rock that normally traps oil and gas. For years, energy companies largely ignored volcanic rock because it was too difficult to map and too unpredictable to drill. Finding a strong gas flow in it changes that thinking, and it suggests there may be much more gas locked away in similar rocks across the Bohai basin.

Third, the flow. During testing, the well produced about 800,000 cubic metres of natural gas a day. That is a test result, not a production rate. A test measures what a well can deliver over a short period under controlled conditions; it does not prove the well will keep producing at that rate for months or years. Even so, a flow of that size from a single exploration well is a strong sign that the area holds a large amount of gas.

CNOOC’s chief scientist and chief geologist, Xu Changgui, said the discovery opens a new prospect for ultra-deep gas exploration in the Bohai Sea. He also said the find could speed up further exploration in the basin and support the company’s longer-term ambition of building a natural gas province in the region with resources totalling one trillion cubic metres.

Why drilling this deep is so hard

Drilling 5,770 metres into the seabed is not simply a matter of drilling further. Every extra kilometre brings new problems, and volcanic rock adds more.

The first problem is seeing underground. Before a company drills, it uses sound waves to build a picture of the rock below the seabed — a technique called seismic imaging. Volcanic rock scrambles those sound waves, so the picture comes out blurred and the gas-bearing layers are hard to spot. CNOOC said it used its own independently developed multi-source broadband three-dimensional (3D) seismic technology, along with new methods for predicting where gas-bearing rock would be, to find the right spot to drill.

The second problem is the drilling itself. At nearly six kilometres down, the drill bit must cut through hard volcanic rock while coping with high pressure and high temperatures. Equipment can fail, the hole can collapse, and each attempt costs far more than a shallow well. That is why ultra-deep wells are drilled only where a company is fairly confident of a reward.

The third problem is time and money. Ultra-deep wells take months to drill and cost many times more than ordinary offshore wells. A company will only commit that kind of money if it believes the area could hold a field big enough to pay for it. CNOOC’s willingness to drill here — and the result it got — suggests it believes the Bohai basin’s deep rocks are worth the gamble.

Where is the Bohai Sea, and why does it matter?

The Bohai Sea is a shallow sea off the coast of northern China, between the Liaodong Peninsula and the Shandong Peninsula, close to the major cities of Beijing and Tianjin. It is one of China’s most important areas for domestic oil and gas production, and CNOOC has been working there for decades.

The well sits near the Bozhong Sag, a deep bowl-shaped dip in the seabed that is the largest hydrocarbon-rich depression in the Bohai Sea. A “sag” is a place where rock layers have sunk down over millions of years, creating the heat and pressure that turn buried organic matter into oil and gas. The Bozhong Sag has already produced one major field: Bozhong 19-6, China’s first offshore gas field with more than 100 billion cubic metres of gas, which entered full production in August 2026.

Bozhong 19-6 shows what success looks like in this area. The field holds proven reserves of more than 200 billion cubic metres of natural gas and over 200 million cubic metres of condensate, a light form of oil that comes out of the ground with gas. Its first phase now produces about 3.5 million cubic metres of natural gas a day and has already supplied more than 2.8 billion cubic metres in total. Building it meant drilling ten ultra-deep wells averaging more than 5,500 metres in depth — a record for the Bohai oilfield at the time.

The new discovery is separate from Bozhong 19-6, but it sits in the same neighbourhood and in the same kind of deep rock. CNOOC expects it to expand exploration opportunities across the region, and the company has already shown in the area that deep wells can work: a separate ultra-deep well drilled to 6,088 metres was producing about 6,300 barrels of oil equivalent a day by July 2024.

What this means for China

China is one of the world’s largest buyers of natural gas, and it still relies heavily on imports to meet its needs. Gas piped in from Central Asia and Russia, and shipped in as liquefied natural gas (LNG) from countries such as Australia and Qatar, fills a large part of the gap between what China produces and what it uses — a gap that grows sharper in winter, as Europe has also found with long-term gas deliveries to Germany. Every new domestic discovery helps reduce that dependence, even if only a little.

Natural gas also matters for China’s climate goals. Gas burns more cleanly than coal, producing less carbon dioxide for the same amount of energy, and China still generates much of its electricity from coal. Replacing coal with gas in power stations, heating and industry is one of the fastest ways to cut emissions without shutting down the energy system overnight. That is why gas discoveries tend to be welcomed even by governments that are trying to move towards renewable energy.

But there is a limit to what this one discovery can do. Gas is still a fossil fuel, and burning it still releases carbon dioxide. The announcement comes as world leaders meet at the COP31 climate summit in Antalya, Türkiye, where countries are arguing over how fast to cut fossil fuel use and who should pay for the damage climate change is already causing. A new gas find does not change that debate — it sits right in the middle of it.

For CNOOC itself, the discovery is also a technology story. The company has spent years building its own deep-drilling and seismic imaging tools rather than relying on foreign firms. If its methods can reliably find gas in volcanic rock, that know-how could be used in other deep basins, in China and elsewhere.

What is still unknown

For all the excitement, the announcement leaves the most important questions unanswered.

CNOOC has not disclosed an estimate of recoverable reserves — that is, how much gas could actually be brought to the surface and sold. Without that number, nobody outside the company can judge how big the find really is. A well that flows strongly during a short test may produce much less over a long period, or the gas may be spread across rock that is too difficult or expensive to drain.

The company has also not given a timetable for commercial production, nor said what it would cost to develop the field. Ultra-deep offshore fields need platforms, pipelines and processing facilities that take years to build and billions of dollars to pay for. The decision to go ahead will depend on gas prices, the cost of development and how the test results look after further study.

In short, this is an exploration result, not a producing field. The well proves gas is there and that it can flow. It does not prove a new gas province yet. The next steps — appraisal wells to map the size of the find, engineering studies and, eventually, an investment decision — will take years.

That caution applies to the one trillion cubic metre figure as well. Xu Changgui described it as a longer-term ambition for a gas province in the Bohai basin, not as a measured reserve for this single well. It is a goal, not a guarantee.

The bigger picture

The Bohai discovery is part of a wider push by energy companies into deeper and harder rocks. As the easy oil and gas runs out, companies are drilling deeper, further offshore and into rock types they once ignored. CNOOC is not alone: energy firms around the world are chasing ultra-deep resources, from the South China Sea to the Gulf of Mexico, betting that better technology can unlock gas that was out of reach a decade ago. Offshore energy is also changing in other ways — Britain, for example, now says it will only back new offshore wind farms that cut household bills, a reminder that the sea is becoming a battleground for both fossil fuels and renewables.

For consumers, none of this will change gas prices tomorrow. A single exploration well, however promising, is years away from feeding gas into homes and power stations. But if the Bohai basin’s deep volcanic rocks turn out to hold as much gas as CNOOC hopes, the discovery could eventually add a meaningful new source of supply for the world’s biggest energy market — and give other companies a reason to look again at the rocks they used to walk past.

Frequently asked questions

What is CNOOC?

China National Offshore Oil Corporation is China’s largest offshore oil and gas producer and one of the country’s three big state-owned energy companies. It operates most of China’s offshore oil and gas fields, including the major fields in the Bohai Sea, and also invests in oil and gas projects overseas.

How deep is 5,770 metres, really?

It is about 3.6 miles, or roughly 19,000 feet. To put it in everyday terms, it is more than six times the height of the Burj Khalifa, the world’s tallest building, and about 640 times the height of a typical three-storey house. The drill had to cut through almost six kilometres of rock below the seabed.

What is an ultra-deep well?

There is no single global definition, but in offshore exploration a well deeper than about 5,000 metres is generally described as ultra-deep. These wells are expensive and technically difficult because of the high pressure, high temperature and hard rock at those depths.

How much gas did the well actually produce?

During testing, the well flowed at about 800,000 cubic metres of natural gas a day — roughly 28 million cubic feet a day. That is a test flow, measured over a short period. It is not the same as a sustained production rate, and CNOOC has not said how much gas the field holds in total.

What is the Bozhong Sag?

It is a large, bowl-shaped depression in the rock beneath the Bohai Sea, and the largest area of oil- and gas-bearing rock in the basin. Over millions of years, organic matter buried in the sag was cooked by heat and pressure into oil and gas, which then collected in the rocks around it. The Bozhong 19-6 gas field, one of China’s biggest offshore gas fields, sits in the same area.

Will this discovery lower gas prices?

Not in the short term. The well is an exploration success, not a producing field. Even if CNOOC decides to develop it, building the platforms and pipelines needed to bring the gas ashore would take years. Any effect on prices would come much later, and only if the field turns out to be large.

Is natural gas clean energy?

Natural gas burns more cleanly than coal and oil, producing less carbon dioxide for the same amount of energy, and it produces almost no soot or sulphur. But it is still a fossil fuel: burning it releases carbon dioxide, and leaks of methane — the main part of natural gas — can add to warming. That is why gas is usually described as a cleaner fossil fuel, not a clean fuel.

Conclusion

CNOOC’s Bohai Sea discovery is a genuine piece of good news for China’s energy industry: a high-yield gas well drilled deeper than almost any other in the country, in volcanic rock that energy companies long considered too difficult to explore. The test flow of 800,000 cubic metres a day is impressive, and the location — next to the Bozhong Sag and the Bozhong 19-6 field — gives the company good reason to keep drilling.

But the find is a beginning, not an ending. No recoverable reserves have been announced, no development plan exists, and no gas will flow to homes or power stations for years. The real test of this discovery will come in the appraisal wells and engineering studies that follow. If they confirm a large, producible field, the Bohai basin could become one of China’s most important gas provinces. If they do not, this will remain what it is today: a promising hole in the seabed, and a reminder of how far — and how deep — energy companies must now go to find new gas.

Sources

• Reuters — China’s CNOOC reports major ultra-deep gas discovery in Bohai Sea: https://www.reuters.com/business/energy/chinas-cnooc-reports-major-ultra-deep-gas-discovery-bohai-sea-2026-11-12/
• OilPrice.com — CNOOC Makes Major Ultra-Deep Natural Gas Discovery in Bohai Sea: https://oilprice.com/Company-News/CNOOC-Makes-Major-Ultra-Deep-Natural-Gas-Discovery-in-Bohai-Sea.amp.html
• Offshore Engineer (OE Digital) — CNOOC Makes Ultra-Deep Gas Discovery in China’s Bohai Sea: https://www.oedigital.com/news/544311-cnooc-makes-ultra-deep-gas-discovery-in-china-s-bohai-sea
• CGTN — Drilling 5,770 meters deep: China makes major breakthrough in ultra-deep gas exploration: https://news.cgtn.com/news/2026-11-12/China-makes-major-breakthrough-in-ultra-deep-gas-exploration-1S0V1IynTHi/p.html
• ECNS — China’s first 100-billion-cubic-meter offshore gas field enters full production (Bozhong 19-6): http://www.ecns.cn/cns-wire/2026-08-10/detail-ihfhziqh0068726.shtml

This article is for general information and education only. It is not legal or financial advice.