Burning combustible ice is the most amazing energy source in the world. In people's impression, water and fire are never compatible, water can put out fire, fire can also devour water. But the magic of combustible ice is that, as a piece of ice solidified by water and the temperature is below 0 ℃, it can burn up like a candle. In fact, it burns much more intensely than a candle.
In 1810, a scientist inadvertently created combustible ice while conducting an experiment. But people at the time didn't know what it was, so they didn't care.
In 1934, the first human discovery of combustible ice was made when American Hamer Schmidt discovered combustible ice in a blocked gas transmission pipeline.
In 1968, Soviet geologists discovered combustible ice within the cold, biting permafrost of Mesoiaha, Siberia, and development began within a decade thereafter.
After the news spread, countries all over the world started to study and explore this kind of ice that can burn.
Combustible ice is not really ice, it just looks like ice, and it is called "combustible ice" because of the characteristic of burning when it meets fire. Combustible ice is actually an ice-like crystalline substance formed by natural gas and water under high pressure and low temperature conditions.
Three basic conditions must be met for combustible ice to form: temperature, pressure, and raw materials. First, combustible ice can be generated above 0°C, but it will decompose when it exceeds 20°C. And the seafloor temperature is generally maintained at about 2~4℃.
Secondly, combustible ice can be generated at 0°C with only 30 atmospheres of pressure, and with the depth of the ocean, 30 atmospheres of pressure is easily guaranteed, and the greater the pressure, the less likely the hydrate will decompose.
Finally, the organic matter on the seafloor settles and the abundant carbon in it is biotransformed to produce an ample source of gas. The stratum of the seafloor is a porous medium, and under the conditions of temperature, pressure and gas source, combustible ice crystals will be generated in between the voids of the medium.
Combustible ice is widely distributed in nature on the slopes of continents, islands, uplifts at the edges of active and passive continents, on the polar continental shelves, and in the deep-water environments of oceans and some inland lakes.
About 27% of the Earth's land is a potential area where combustible ice could form, and about 90% of the ocean is also in such a potential area. In the submarine area alone, combustible ice is distributed over 40 million square kilometers, accounting for 1/4 of the total area of the Earth's oceans. 2011, as many as 116 combustible ice distribution areas have been discovered in the world, and the thickness and scale of its mineral layers are incomparable to those of conventional natural gas fields.
Scientists estimate that globally, there are twice as many reserves of combustible ice as there are existing reserves of natural gas and oil, enough for more than 1,000 years of human use.
And China's combustible ice reserves are very considerable, ranking first in the world. According to preliminary predictions, the combustible ice resources in China's waters are about 80 billion tons of oil equivalent. The sea located in the northern slope of the South China Sea in China is a combustible ice rich area, with a forecast reserve of about 19.4 billion cubic meters, which is quite rare. On land, China's tundra also contains a large amount of combustible ice, and in 2009, experts predicted that the combustible ice reserves on the Qinghai-Tibet Plateau reached 35 billion tons of oil equivalent.
The biggest advantage of combustible ice over traditional energy sources, coal and oil, is its low pollution and high calorific value. Scientific experimental data show that after burning combustible ice, only a small amount of carbon dioxide and water will be produced, pollution is far less than coal and oil, and the pollution to the environment is extremely low. However, it produces 10 times more heat than traditional energy sources, and 1 cubic meter of combustible ice can be converted into 164 cubic meters of natural gas and 0.8 cubic meters of water.
In the context of global energy resources tension and increasingly serious environmental pollution, combustible ice, as a new type of energy with abundant reserves, high calorific value and low pollution, will certainly change the global energy landscape if it can be exploited by human beings on a large scale.
However, currently, countries around the world, including China, have not yet exploited combustible ice on a large scale, which is why?
The main reason is that combustible ice is usually located in areas with harsh natural environments, such as the bottom of the ocean at a depth of hundreds or thousands of meters, making it extremely difficult to mine, and countries around the world are currently very cautious about this.
There are many mining methods for combustible ice, such as thermally excited mining, decompression mining, chemical reagent injection mining, CO2 replacement mining and solid mining. However, these methods are not mature enough technically and economically.
The extraction of combustible ice can change the temperature and pressure conditions under which it occurs, causing the decomposition of gas hydrates. If the temperature and pressure conditions are not effectively controlled during the extraction of combustible ice, a series of environmental problems may arise, such as the intensification of the greenhouse effect, changes in marine ecology, and submarine slip events.
For mankind, there is still a long way to go for large-scale mining and utilization of combustible ice. However, it is encouraging to note that China is already at the forefront of the world in the exploitation of combustible ice.
In 2017, China's "Blue Whale No. 1" conducted test mining operations of combustible ice in the South China Sea. The test mining operation lasted for 60 days and produced more than 300,000 cubic meters of gas in total, achieving a number of major breakthrough results such as the longest continuous gas production time, the largest total gas production, stable airflow and environmental safety, creating a world record for the length of gas production and total gas production.
In 2020, China conducted a second round of test mining operations of combustible ice in the Shenhu Sea in the South China Sea. In this round of test mining for 1 month, the total gas production reached 861,400 cubic meters, which is 2.8 times of the total gas production in 60 days in the first round. The test production has overcome the core key technology of drilling horizontal wells in shallow and soft strata in deep sea and achieved a significant increase in gas production scale, which has laid a solid technical foundation for productive test production and commercial exploitation. As a result, China became the first country in the world to adopt horizontal well drilling technology to test-mine gas hydrate in the sea.
