Text | "China Science News" reporter Li Sihui
"In the event of a war, the gas storage tanks on the ground are vulnerable to air strikes, and with the underground gas storage, the other side will not be able to fight! Academician Grandpa, am I right? ”
Not long ago, in a popular science activity for academicians on campus, in the face of questions from teenagers, Yang Chunhe, academician of the Chinese Academy of Engineering and researcher of the Wuhan Institute of Rock and Soil Mechanics of the Chinese Academy of Sciences, nodded with satisfaction and said: "You are very right. But there's more to underground energy storage than that. ”
Yang Chun and Chen Jirong/photo
Why is it hidden in the ground?
Energy security is an important part of national security. To ensure energy security, we must attach great importance to energy storage security. There are many ways to store energy, and deep energy storage is a very important one.
For more than 20 years, Yang Chunhe has always focused on one thing - to carry out research on energy storage in underground salt caverns.
"Even in a peaceful environment, we need to 'hide' energy underground!" Yang Chunhe said that the current energy structure and energy storage status of the mainland determine that we must ask for space underground and carry out underground energy storage.
He has introduced on many occasions that "deep salt cavern energy storage" is one of the important ways of underground energy storage, which refers to the use of the goaf left after salt mining, or a huge "natural cave" in the underground salt rock to store oil, natural gas, hydrogen, helium and carbon dioxide and other energy substances, which has the advantages of large reserves, low cost, good sealing and long service life.
The mainland is a major energy consumer, and accelerating the utilization of non-fossil clean energy is a major strategic need for the upgrading and transformation of the mainland's energy structure and the realization of the "dual carbon" goal. However, since energy sources such as wind and solar energy are typically regional and cannot be supplied in a continuous and stable manner, it is necessary to store the generated electricity in order to make full use of it.
How to store it? Scientists have come up with many methods, including pumped hydro storage, compressed gas storage, hydrogen energy storage, flow battery energy storage, etc. Either way, you'll need a lot of storage space. Deep underground space, which has the advantages of large volume and high pressure, has become an ideal place for energy storage.
The use of deep underground space to store oil can avoid the shortcomings of using surface storage tanks for oil storage, such as poor economy, low safety and large floor area, and further ensure the safe supply of oil. Speeding up the construction of underground gas storage can also ensure the stable supply of natural gas through long-distance pipelines and avoid large-scale "gas shortages".
How can you fall behind?
In 1999, after receiving a Ph.D. in geological engineering from the University of Nevada, Yang Chunhe returned to China and joined the Wuhan Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, becoming the first returnee to become the institute's first returnee doctorate.
At that time, there were more than 60 salt caverns in the U.S. strategic oil reserves, with an oil storage capacity of more than 700 million barrels. These oil reserves not only ensure U.S. energy security, but also establish U.S. dominance in international oil price pricing. At that time, the mainland did not even have a salt cavern reserve.
"After returning to China, I found that there were very few people on the mainland who were engaged in this kind of research." Yang Chunhe said that he called for attention to underground energy storage on many occasions, when some people of insight in China gradually realized the importance of oil and gas strategic energy storage, and some large energy companies put forward similar needs, but they suffered from a blank of related domestic projects, no technology, no talent, and no mature experience to follow.
The needs of the country and the industry are the research directions of scientists! Yang Chunhe is determined to be "the first person to eat crabs".
"Use the goaf left over from the mining of salt mines on the mainland to store natural gas." When he first put forward the idea publicly, there was an uproar in the industry, and there was a lot of opposition.
Some people believe that China's geological structure is extremely complex and cannot complete the construction of this project - the continental salt layer is a layered structure, the salt layer thickness is small, there are many insoluble interlayers, and the geological conditions are more complex than imagined. Experts from developed economies such as Europe and the United States have encountered similar geological conditions, and most of them have directly given up on building reservoirs.
From a safety point of view, some experts are worried about major safety accidents such as leaks, collapses and even explosions in underground gas storage.
In the face of doubts, Yang Chunhe did not defend too much. With equipment and luggage, he led the team to carry out on-site investigations in many provinces, including Jintan in Jiangsu, Qianjiang in Hubei, and Pingdingshan in Henan...... On the vast territory of China, almost all the underground space of salt rock that can be used to store oil and gas has left the footprints of Yang Chun and his team.
After nearly 2,000 sets of tests, he and his team members finally came to a conclusion that the stability and tightness of China's salt caverns are completely reliable, safe and applicable for underground oil and gas reserves.
"There are more solutions than difficulties. What foreigners can do, Chinese can do; What foreigners think is difficult to do, Chinese may not be able to do it with more effort and wisdom! The key technology of salt cavern gas storage should be in our own hands, and our country's own gas storage should be built. Yang Chunhe and his team used scientific data to prove that China's salt caverns are completely reliable for underground oil and gas reserves.
In 2003, the mainland's west-to-east gas transmission project needed to build supporting gas storage, and Yang Chun and his team's theoretical innovation finally had the opportunity to be applied. He suggested that the first salt cavern gas storage should be located in Jintan, Jiangsu, and the use of the cavity left after the mining of Jintan salt mine could save 125 million yuan in construction costs and save 5 years in construction time. The highly actionable professional advice has been supported by relevant departments and units.
In 2007, Jiangsu Jintan Gas Storage was officially put into operation for gas injection, becoming the first underground salt cavern gas storage in mainland China and even Asia. As of January 19, 2024, the cumulative gas production capacity of the "No. 1 Salt Cavern Gas Storage Reservoir in China" has exceeded 5 billion cubic meters, which can meet the gas demand of 16 million households in the Yangtze River Delta region during the peak shaving period. Behind this, a lot of hard work of Yang Chunhe is condensed.
In 2015, a micro-permeable layer was found in Jintan gas storage, and gas leakage occurred. Yang Chunhe was ordered to carry out technical research.
After repeated analysis and judgment, he and his team proposed a new technology - using salt rock recrystallization to plug the gas storage, and quickly carried out the research on the recrystallization of the key micropermeable layer of the Jintan gas storage. In the end, the problem of micropermeable layer plugging was successfully solved.
"Not only should the salt cavern gas storage take root in China, but it must also blossom and bear fruit in all directions." Yang Chunhe is quite proud that for more than 20 years, he has led the team to participate in the technical research of nearly 10 salt cavern gas storage projects, which has provided an important guarantee for the first and second lines of the mainland's west-to-east gas transmission and the Sichuan-to-East gas transmission project. At present, more than 90% of the underground gas storage in mainland China is supported by the team.
After decades of development, what is the current level of underground energy storage in the world?
Yang Chunhe said frankly that China and developed countries in Europe and the United States are all doing research, and the United States and Germany started decades earlier than us, and were once far ahead of us. Now, we're technically on the same level as them. At first glance, everyone is "running side by side", but in fact, the geological environment of the continent is much more complex than them, and the problems that need to be solved are much more difficult.
He bluntly said that Western scientists in the field of geological engineering have never encountered such complex geological conditions as China, so their technical route cannot solve China's problems. On the contrary, Chinese scientists are not only able to cope with the complex geological environment in China, but also solve the technical problems of underground reservoir construction in Western countries with considerable ease. Therefore, the technological level of Western countries is not at the same level as China.
How will it be laid out in the future?
"The '0 to 1' task of the mainland's underground gas storage has been completed, and now we need to classify the strata and figure out which places are suitable for storing which energy." In addition to oil and gas storage, in recent years, Yang Chunhe has also set his sights on hydrogen and helium storage.
Hydrogen energy has the advantages of wide sources, high calorific value, no pollution, and rich application scenarios, and the effective use of hydrogen energy is an effective way to solve the sustainable development of energy. Yang Chunhe believes that large-scale hydrogen storage is a key link in the development of the hydrogen energy industry.
He has repeatedly suggested that Hubei Province rely on the rich salt resources in some areas of the province to build large-scale hydrogen energy reserve projects and build an energy storage base in the central part of the mainland. Under his appeal, Daye City, Hubei Province, which was once famous for its mineral resource exploitation, took the lead in carrying out underground hydrogen storage practices in the country.
In March 2023, Daye City's "Integrated Hydrogen Energy Mine Comprehensive Construction Project for Green Electricity and Green Hydrogen Production, Storage and Processing in Mining Areas" officially started. This is the first scientific research project of cave hydrogen storage technology in the mainland, and after completion, it will become the second cave hydrogen storage project in the world.
"Underground space is a treasure trove, according to our technical route construction, in the future, suitable formations can store oil, hydrogen, and helium, to achieve multi-scenario, multi-element comprehensive application." Yang Chunhe said.
Yang Chunhe hopes that the development of the project and the breakthrough of technical bottlenecks can provide technical support for the large-scale and safe storage of hydrogen energy, provide a joint test base for the research and development personnel of hydrogen storage in deep caverns across the country, and provide technology and standards for the promotion of large-scale hydrogen storage across the country.