How powerful is “Deep Sea One”?

Editor's Note

In the past 2021, all walks of life followed the development path outlined in the "14th Five-Year Plan", supported by scientific and technological innovation, and made solid efforts to achieve one remarkable achievement after another. Science and Technology Daily launched a special plan during the two sessions, focusing on major breakthroughs in industries such as energy, aerospace, and transportation, reporting on the innovation process behind them, and showing their contribution to economic and social development.

◎ Science and Technology Daily reporter Cao Xiuying

Cumulative natural gas production exceeds 1 billion cubic meters!

Not long ago, my country's first self-operated 1,500-meter ultra-deepwater gas field, "Deep Sea One", delivered an impressive performance since its official production.

In the Lingshui waters of Hainan, the world's first 100,000-ton deep-water semi-submersible production and storage platform, "Deep Sea One", stands proudly on the blue sea like an oversized "giant".

It can extract natural gas from 1,500 meters underwater, connect it to the national natural gas pipeline network through submarine pipelines, and then transport the separated condensed oil to land by tankers.

From the 1,500-meter deep sea to the stoves of thousands of households, natural gas only needs one day to complete this "journey". Behind this is the unremitting exploration of several generations of Chinese offshore oil workers towards the "deep blue".

From following to taking the historic lead in achieving three world-class innovations and 13 domestically first-of-its-kind technologies, "Deep Sea One" represents a major breakthrough in my country's deepwater oil and gas development and deepwater marine engineering equipment technology.

Find "treasures" in abandoned areas

On June 25, 2021, the commissioning ceremony of the "Deep Sea No. 1" ultra-deepwater gas field of China National Offshore Oil Corporation (CNOOC) was grandly held at the Beijing and South China Sea gas field sites.

The "Deep Sea No. 1" gas field is about 150 kilometers away from Sanya City, Hainan Province. The water depth in the sea area is 1,220 to 1,560 meters, and the east-west lateral span of the gas field reaches 50 kilometers.

In 2006, CNOOC cooperated with well-known foreign oil companies to explore the Qiongdongnan Basin, and drilled the first deepwater well in the central canyon of the block in 2010, achieving a breakthrough in deepwater exploration in the western South China Sea.

However, since then, due to the small scale of reserves in a single block and layer of the deepwater well, the lack of development economics, and the lack of understanding of the oil and gas accumulation conditions in the Central Canyon, well-known foreign oil companies withdrew from the exploration rights of the block in 2012.

The Chinese offshore oil workers who dared to be the first did not give up. From a global perspective, since the new century, the pace of global offshore oil and gas exploration and development has accelerated significantly, the total reserves of newly discovered offshore oil and gas have exceeded those on land, and the reserves and production have continued to grow, making it a strategic successor area for global oil and gas resources.

If we count from the Yinggehai oil seedling survey in 1956, my country's offshore oil industry has gone through more than 60 years of development. Entering deep water will become the next strategic goal of China's offshore oil.

On August 18, 2014, a huge orange flame burst out from the burning arm of the drilling platform, instantly illuminating the South China Sea at night. The "Offshore Oil 981", China's first independently designed and built sixth-generation deepwater semi-submersible drilling platform, drilled a large gas field "Deep Sea No. 1" in the Lingshui 17-2 block and harvested a high-yield oil and gas flow in the test.

This is the first important discovery in the deepwater field since the commissioning of the "Haiyang Shiyou 981" deepwater drilling platform, and it also proves the huge natural gas resource potential in the Qiongdongnan Basin of the South China Sea. After that, CNOOC successively explored and discovered several deepwater gas fields in the sea area, and the energy treasures in the depths of the South China Sea gradually appeared before the world.

The discovery of these deep-sea gas fields is due to the persistence of my country's marine oil workers in exploration technology theory and basic research.

"In the past, large foreign companies used the traditional Atlantic passive margin theory, which is not applicable to us," said Xie Yuhong, chief scientist of CNOOC. "We inherited the traditional oil and gas exploration technology theory, strengthened basic geological research, established a deepwater oil and gas accumulation model, improved deepwater oil and gas exploration technology, and found the Lingshui 17-2 structural group with large exploration potential in the central canyon waterway of the Qiongdongnan Basin."

"Thermos Flask Liner" is an international first

1,500 meters is usually defined as the dividing line between deepwater and ultra-deepwater internationally. Although ultra-deepwater areas are rich in oil and gas resources, every step deeper is "as difficult as ascending to heaven" - with every meter increase in water depth, pressure, temperature, and flow will change dramatically. A set of equipment and facilities installed 1,500 meters underwater is subject to pressure equivalent to a person weighing 300 kilograms standing on a fingernail. In addition, deepwater development has extremely high requirements for technology, equipment capabilities, and key design indicators. Only a few large oil companies in the world have the technical capabilities for deepwater development.

Therefore, when the "Deep Sea No. 1" ultra-deepwater gas field was discovered in 2014, most people's reaction was to cooperate with foreign countries and jointly exploit it.

However, at that time, the international oil price was falling sharply, and international oil companies began to back out. Coupled with other objective reasons, the "Deep Sea No. 1" energy station embarked on the road of independent innovation.

What to do when faced with such a huge challenge and task? CNOOC had already mastered the development of oil and gas fields at a water depth of 300 meters, but had little practical experience in deepwater gas fields.

In the fall of 2014, the design of the development plan was put on the agenda. The 35-year-old Li Da became the deputy project manager and the person in charge of the floating body.

"We started the research in October 2014 and proposed the option of building a semi-submersible production platform with oil storage in May 2015," said Li Da.

The industry was shocked. Few people could have imagined that the CNOOC people, who had never independently conducted deepwater design before and were "answering questions independently" for the first time, would choose a path that even their foreign deepwater counterparts had never thought of - borrowing the principle of "thermos bottle liner" to create a world precedent for semi-submersible platform column oil storage.

According to the conventional design of similar oil and gas fields in the world, building a new condensate oil export pipeline is a technically feasible solution, but this will increase the cost by about 800 million yuan.

Can we design a platform that can not only meet the production needs of the gas field, but also temporarily store a small amount of condensate? A new idea flashed in the design team.

They set up 5,000 cubic meter condensate oil tanks in each of the platform's four floating columns and installed tailor-made "protective armor" for the oil tanks, which not only solved the condensate oil storage problem but also avoided the risk of oil leakage due to collision.

This innovative move, known as "U-shaped isolation and safe storage technology for condensate oil", has set a world precedent for oil storage on semi-submersible platform columns.

Subsequently, "Deep Sea No. 1" gave birth to two other world firsts: 50,000-ton super-large structure large deformation semi-floating precision closure technology, and the world's largest tonnage open structure pre-skewed return load lateral transfer technology. At the same time, it used 13 domestic first technologies such as the design and installation technology of the 1,500-meter-deep polyester cable mooring system, and the design and detection technology of the floating structure fatigue that does not need to be docked for maintenance for 30 years.

The pace of "diving" into the deep sea continues

The commissioning of "Deep Sea No. 1" is a major breakthrough in my country's deepwater oil and gas development and marine engineering equipment technology, marking a historic leap in my country's marine oil exploration and development capabilities from 300 meters deep water to 1,500 meters ultra-deep water.

The successful production of 1 billion cubic meters at the "Deep Sea No. 1" gas field has verified the advancement and reliability of my country's independently created complete technical system for deep-water oil and gas resource exploration, development, production, and operation and maintenance. It also marks that my country has entered the ranks of advanced countries in deep-sea oil and gas exploration and development.

After the "Deep Sea No. 1" energy station is put into operation, the natural gas produced will be connected to the national natural gas pipeline network through submarine pipelines, and will provide a stable supply of 3 billion cubic meters of gas to Guangdong, Hong Kong, Hainan and other places every year.

At present, with "Deep Sea No. 1" as an important hub, CNOOC is actively promoting the development of gas fields such as "Deep Sea No. 2" (Lingshui 25-1), and pushing the construction of the trillion-dollar gas zone in the South China Sea from blueprint to reality, so as to better meet the growing clean energy needs of the Guangdong-Hong Kong-Macao Greater Bay Area and the Hainan Free Trade Zone (Port).

What is even more valuable is that deepwater projects represented by the "Deep Sea No. 1" gas field have not only driven the development of my country's national industries such as shipbuilding, steel, and mechanical and electrical industries, but also made China National Offshore Oil Corporation a firm practitioner of high-quality joint construction of the "Belt and Road" and deepening of international energy cooperation.

Source: Science and Technology Daily

Editor: Zhang Shuang

Review: Julie

Final judge: Wang Yu