On May 10, 2017 (April 15, 2017 lunar calendar), our country's first combustible ice test production was successful. China's first natural gas hydrate (combustible ice) test production was successful in the Shenhu sea area in the northern part of the South China Sea. The natural gas hydrate in the Shenhu sea area of the South China Sea officially started test production on March 28, 2017, and was successfully ignited at 2:52 pm on May 10, 2017. As of 3:00 pm on May 17, the total gas production for 7 consecutive days was 113,200 square meters, the average daily output was 16,000 square meters, and the highest instantaneous daily output was 35,000 square meters. The methane content reached 99.5%. The trial production was normal before the day, and the output was stable, exceeding the scheduled target. Our country became the first country in the world to achieve continuous and stable gas production in the trial exploitation of combustible ice in the sea. On the same day, the State Council sent a congratulatory message on the successful trial production of natural gas hydrates in the sea area. Combustible ice refers to natural gas hydrates, which are distributed in deep-sea sediments or permafrost on land. Ice-like crystalline substances formed by natural gas and water under high pressure and low temperature conditions are mostly white or light gray. Because of its ice-like appearance and flammable in case of fire, it is called combustible ice, also known as solid gas or gas ice. Combustible ice contains 80% to 99.9% methane, and only a small amount of carbon dioxide and water is generated after combustion. The pollution is much smaller than that of coal, oil, and natural gas, but the energy is higher than that of coal, oil, and natural gas. Moreover, the reserves of combustible ice are extremely rich. It is estimated that the total resources of organic carbon contained in combustible ice are equivalent to twice the total amount of known coal, oil and natural gas in the world. The predicted prospective resources in the South China Sea of our country alone have nearly 80 billion tons of oil equivalent. The world's resources are about 2.10 quadrillion cubic meters, and the global reserves are enough for human use for 1000 years. Therefore, it is known as the most ideal potential alternative energy in the 21st century and is an important strategic resource in the world. Combustible ice exists in sedimentary layers hundreds of meters to more than 1,000 meters below the deep sea floor with water depths greater than 100-250 meters and greater than 400-650 meters. The pressure and temperature conditions here can keep combustible ice in a stable solid state. The mining of combustible ice is extremely difficult. It is difficult to mine in an orderly, controllable manner, and without secondary disasters such as geology. Combustible ice is formed under high pressure and low temperature conditions. Once it loses pressure or the temperature rises, combustible ice will turn into gas and increase in volume by more than 160 times. Mining in permafrost is relatively difficult. In the seafloor, there is water and rock, some silt has combustible ice, and some rock layers also store combustible ice. Once the borehole is not well sealed, a large amount of seawater is poured into it, which may cause more instability in a wide range, a large amount of greenhouse gas spillage, and even cause submarine landslides and greater disasters. Because the greenhouse effect of methane is 20 times that of carbon dioxide, if the methane in the combustible ice on the seafloor is accidentally allowed to escape into the atmosphere, it will have unimaginable consequences. The current mining methods are mainly in traditional mining: thermal excitation mining, decompression mining, chemical reagents such as mining, and new mining: carbon dioxide replacement mining and solid mining. At present, more than 40 countries have successively carried out research and exploration of natural gas hydrates. The countries with active research and development of combustible ice globally include China, the United States, Japan, Canada, South Korea, and India. Countries are competing to invest heavily in the trial production of natural gas hydrates, and the competition is extremely fierce. Among them, the United States and Canada have conducted trial production on land, but the effect is not satisfactory. Japan successfully separated natural gas from the combustible ice gas field in the South China Sea Trough in Japan in March 2013, but after six days of trial production, the trial production was forced to stop due to technical problems such as sand production. The second test production was carried out in the same sea area in April 2017. The first test well produced a total of 35,000 cubic meters of gas, and the gas production was stopped again on May 15 due to sand production problems. Compared with the combustible ice mines tested in Japan, the waters of our country are mainly mud silty sand reservoirs, which are also the storage type accounting for more than 90% of the world. The fine sand leads to worse penetration rate. At the same time, the combustible ice in our country has a large water depth and a shallow buried layer, which is more difficult to construct. The test production of combustible ice in our country's waters will use a deep-water semi-submersible platform to mine through pressure reduction. First of all, the platform from the mobilization position to the operating well position, and then a series of test production procedures such as drilling, installation of experimental equipment, and depressurization gas testing, until the ignition test production is successful. Our country's breakthrough in combustible ice drilling and production technology in sea areas is of great significance and a historic breakthrough. As the largest country in the world's energy consumption, our country started late in combustible ice projects, but now our country's combustible ice mining technology leads the world. This not only shows that the core technology of natural gas hydrate exploration and development in our country has been verified, but also marks that China's comprehensive strength in this field has reached the top level. Q & A What is combustible ice? Combustible ice, which is what we call natural gas hydrate, is an ice-like crystalline compound formed by natural gas and water under high pressure and low temperature conditions. From the appearance, combustible ice looks like white or light gray ice and snow crystals. At this time, if there is a source of fire, it can be ignited like solid alcohol, so it is called "combustible ice". What can be done? Combustible ice is a solid compound of natural gas and water combined, similar in appearance to ice. Because it contains a lot of flammable gases such as methane, it is highly flammable. Under the same conditions, combustible ice generates dozens of times more energy than coal, oil, and natural gas, and does not produce any residue and exhaust gas after combustion, avoiding the most troublesome pollution problems. Scientists are so lucky that they call combustible ice "the energy of the future". What are the characteristics? The biggest feature of combustible ice is its high energy density. It occupies a small size, but contains a lot of energy. For example, if a car powered by natural gas can run 300 kilometers with 100 liters of natural gas at a time, then add the same volume of combustible ice and the car can run 50,000 kilometers. If the same volume of solid alcohol and combustible ice are ignited at the same time, the combustion time of combustible ice is much longer than that of solid alcohol. Combustible ice is like the "energy block" that robots compete for in "Transformers". It occupies a small size but contains immeasurable energy. In fact, 1 cubic meter of combustible ice can decompose and release more than 160 cubic meters of natural gas. What are the risks? The use of combustible ice has broad prospects, but there are also risks. It is estimated that the total amount of methane in the global seabed combustible ice is about 3,000 times the total amount of methane in the earth's atmosphere. If careless mining leads to a large amount of methane gas leakage, it may cause a strong greenhouse effect. How to safely and economically exploit combustible ice and separate methane gas from it remains the core problem in the research and utilization of combustible ice in various countries. The difficulty of mining is afraid of loss of pressure and high temperature. Zheng Junwei, director of the editorial department and researcher of "Natural Gas Geoscience", said that the difficulty of mining combustible ice is not to extract it from the seabed or permafrost. The difficulty lies in orderly, controllable, and no secondary disasters such as geology. Zheng Junwei explained that natural gas hydrates are combustible ice, which is formed under conditions of high pressure and low temperature at the same time. Once the pressure is lost, or the temperature rises, the combustible ice will turn into gas and increase in volume by more than 160 times. In permafrost, the difficulty of mining is relatively small. Fear of "submarine landslides" On the seabed, there is water and rocks, some silt has combustible ice, and some rock layers also store combustible ice. Once the borehole is not well sealed, a large amount of seawater is poured into it, which may cause a wider range of instability, a large amount of greenhouse gases escape, and even cause submarine landslides and greater disasters. In the article "Combustible Ice, How Far is It from Large-scale Exploitation" published by Gao Datong of the School of Chemical Engineering of China University of Petroleum (East China), when quoting relevant scholars, the trap of "submarine landslides" is also mentioned. Zheng Junwei concluded that, therefore, the key technology for combustible ice mining is still drilling technology. If it can ensure orderly, smooth and continuous natural gas production, it will be a big breakthrough. He initially estimated that due to technical and economic factors, commercial mining of combustible ice may take another 10 to 20 years. Fear of "sand production" problems In March 2013, the Japanese deep-sea drilling ship "Earth" (Chikyu) conducted the world's first offshore combustible ice test mining. But on the sixth day of the test mining, the operators observed a sudden increase in water production rate, an immediate increase in downhole pressure, and gas production stopped, and sand production was obvious. Due to the difficulty in dealing with this sand production problem, the mining work was suspended, and the operators were unable to recover the underground production equipment. The main component of combustible ice that is particularly easy to decompose is methane, which is the main component of natural gas used by people in daily cooking. Researchers use liquid nitrogen to create low temperature conditions in the laboratory. The synthetic combustible ice has high purity and no gravel, so it is snow-white. But in permafrost, silt, and rock, combustible ice looks like ore because it is mixed with gravel. It can be ignited like solid alcohol. Once combustible ice is mined, if it is not stored in liquid nitrogen, it will decompose and methane gas will escape. Combustible ice is regarded by various countries as a strategic alternative energy source for oil and natural gas in the future. It is a strategic resource that attracts the attention of the world. It is also of great significance to our country's energy security and economic development. " In 1998, compared with the international exploration and study of combustible ice as early as the 1960s, our country's combustible ice research started later than 1998, but it took less than 20 years for Chinese scientific and technological workers to complete the whole process from blank to catch up. In 2007, combustible ice was drilled in the Shenhu Sea, which made our country the fourth country to drill combustible ice on the seabed through national research and development programs after the United States, Japan and India. In 2015, our country's scientific and technological workers accurately located two combustible ice ore bodies in the Shenhu Sea. In 2016, geological survey staff carried out 8 drilling stations in the Shenhu Sea around the test mining, and all of them found combustible ice. At 9:20 on May 10, 2017, the test production of combustible ice in Shenhu sea area began, and after 5 hours and 32 minutes, the test production ignition was successful. As of the 18th, after the test gas ignition, the test production has been continuous for more than a week, the maximum output 35,000 cubic meters/day, the average daily output exceeded 16,000 cubic meters, the cumulative gas production 120,000 cubic meters, the natural gas production is stable, and the methane content is up to 99.5%.