<h1 class="pgc-h-arrow-right" data-track="1" > introduction </h1>
More than 13 billion years ago, a big bang formed the present universe. At first, various elements floated aimlessly in the universe, collided and merged with other elements, slowly formed matter, and finally evolved into planets such as Earth and various celestial bodies.
Since then, various substances on the earth have changed over time, forming various resources such as oil, minerals, and natural gas that we need today.
Tips: When the solar system was formed, the dust in the universe was re-aggregated due to the gravitational field, which contained most of the elements on the earth, and these elements fell on the earth with meteorites to form a metamorphic state, and the monomer state existed in the soil circle, and the enriched part became an ore vein, and the three major fossil fuels, that is, the organic matter of nature, circulated through the organism.
The time required to form these resources is very long, it cannot be regenerated in a short period of time, and human civilization is developing rapidly, and the formation rate of various resources is far from keeping up with the rate of human exploitation and consumption.
<h1 class="pgc-h-arrow-right" data-track="5" > combustible ice: a cleaner new energy source that is more efficient</h1>
This kind of traditional energy is very easy to pollute the environment when used, and the disposal of exhaust gases is a rather difficult problem. Scientists began to study and find more efficient and clean new energy sources, such as combustible ice is one of the more successful examples. Combustible ice actually refers to methane gas water clathrates, and water contains a large amount of methane in a solid form with a lattice.
Tips: In 1934, American Hammer Schmidt found burning ice in a blocked gas pipeline, the first time a human discovery of "methane gas hydrate."
Combustible ice is often found at the bottom of shallow oceans or in sediments deep in the ocean. Scientists speculate that this substance is formed by natural gas and water at high and low pressures. Combustible ice has the characteristics of wide distribution, large total amount and high energy density, and is considered to be the most promising new alternative energy source.
<h1 class="pgc-h-arrow-right" data-track="8" > the difficulty of extracting combustible ice</h1>
The biggest challenge now is the way combustible ice is mined. Because combustible ice is extremely unstable at room temperature and pressure, it is impossible to directly mine like mineral deposits, and there are three ideas for the mining method proposed so far, one is pyrolysis, the other is the pressure reduction method, and the third is the carbon dioxide replacement method.
It is worth mentioning that the third method will cause a large amount of methane to leak, causing a much more serious greenhouse effect than carbon dioxide, which will pose a very serious threat to the earth's environment. If all the methane on the earth in a frozen state is thawed, it may even lead to species extinction.
While most countries are still overcoming the problems of mining and transporting combustible ice, China has completed the trial mining of combustible ice in May 2017, and at the same time, China is still conducting research and development of other new energy sources.
In the same year, China drilled 236 degrees Celsius hot dry rock for the first time in the Qinghai Gonghe Basin, and a large number of available hot dry rock resources were found here. On the road to discovering the use of new energy sources, China has taken another significant step.
<h1 class="pgc-h-arrow-right" data-track="13" > geothermal resource: hot dry rock </h1>
So, what is hot dry rock?
Hot dry rock actually belongs to a kind of geothermal resources. Geothermal energy comes from the heat emitted by the core of the Earth, which heats the magma until it is piping hot as it passes through the mantle, and then transmits it to the outermost crust. At the same time, it is also the "culprit" that triggers volcanic eruptions and earthquakes.
At present, we can only develop the geothermal resources of the shallow crust, which requires suitable geological conditions, such as where the crust breaks, or the edge of the plate tectonics.
If one day we can invent the technology to develop deep geothermal resources, then our energy problems will naturally be solved. Because geothermal energy coexists with the earth, as long as the earth still has vitality, geothermal energy will be endless.
Tips: The composition of this rock mass can vary greatly, most of which are mesozoic intrusive rocks, but they can also be Metamorphic rocks of the Mesozoic Era, or even massively thick bulk sedimentary rocks.
<h1 class="pgc-h-arrow-right" data-track="18" > human use of geothermal resources </h1>
Humans have been using this energy for a long time, and in the early days they only used water sources that had been heated by geothermal heat, such as hot springs and underground hot water for heating.
In modern times, when science and technology are more advanced, geothermal energy is mostly used in agriculture, such as building greenhouses to cultivate crops, controlling environmental water temperature to improve the efficiency of aquaculture, and so on.
It was not until the 1950s or so that people really realized the availability of geothermal resources and began to develop and use them further. Today, this energy source is mostly used to generate electricity, and people often build geothermal power stations in areas rich in geothermal resources.
Tips: China currently uses 20 ~ 25 ° C as the lower limit of hot water, most of the foreign countries use 20 ° C as the temperature limit of hot and cold water, but generally call groundwater higher than the local average annual temperature as hot water.
<h1 class="pgc-h-arrow-right" data-track="22" > Iceland: a country rich in geothermal energy </h1>
At present, various countries have made different attempts at the further development and utilization of geothermal energy, and some places can make full use of geothermal resources by virtue of geographical advantages, such as Iceland, which is crossed by the mid-Atlantic ridge. Just by hearing the name, we might think it's a very cold country, but in fact, Iceland is not cold.
Iceland is located between two large geological plates, and there is a wealth of geothermal energy under the ground, and almost all of Iceland's electricity is provided by this geothermal energy. With this timing and location, Iceland has become the country with the highest utilization rate of clean energy in the world. It is precisely because of these rich geothermal resources that Iceland, although it looks icy and snowy, is full of hot springs.
<h1 class="pgc-h-arrow-right" data-track="25" > the mining and utilization of hot dry rock </h1>
Geothermal resources are divided into hydrothermal type and hot dry rock type。 Among them, the hot dry rock type has much more resources than the hydrothermal type. There is no consensus among various countries on the definition of hot dry rock.
However, usually we think of hot dry rock as a kind of hot rock mass buried 3 to 10 kilometers underground, with a temperature greater than 180 degrees Celsius, and the interior is dense and impervious. When we mine hot dry rock, we can artificially create a crack in this rock mass, inject cold water from the crack, and wait until the cold water is heated into hot water and water vapor before extracting the heat.
Some researchers say that geothermal resources are generated by the earth's core, so as long as the depth is sufficient, hot dry rock can be developed anywhere.
Tips: The use of hot dry rock to generate electricity, only need to invest manpower and material resources in the early stage of drilling, after the completion of the project, relying on its own energy to convert the electricity to maintain the power generation equipment to continue to operate.
Hot dry rock is efficient, clean, and renewable. In the development of hot dry rock, it is safe and environmentally friendly, and it is possible to save energy while having high efficiency.
Moreover, hot dry rock also has the advantages of thermal energy continuity not affected by seasonal climate and low cost, and has now become a new energy source widely concerned by the world.
Tips: China's hot dry rock accounts for 98% of all geothermal resources, while hydrothermal geothermal resources account for only 2%.
The world's first project to utilize hot dry rock resources was initiated by the United States in 1974, and in the course of this project, the United States used the hydraulic fracturing technology that previously exploited shale gas, and produced a maximum temperature of 192 degrees Celsius of hot dry rock.
In 2008, the Massachusetts Institute of Technology in the United States published a research report called "The Future of Geothermal Sources", in which the idea of enhancing geothermal system technology was proposed, and it was believed that this technology could be used to mine hot dry rock. Moreover, the United States is very promising to commercialize the use of hot dry rock mining technology in the next 10 to 15 years.
When we first used geothermal energy, most of them were directly utilized hydrothermal geothermal resources, and there were not often abundant water resources near hot dry rocks.
The working method of the enhanced geothermal system is to widen the gap between the formations by injecting cold water, so that the circulation effect of groundwater is better, and then the geothermal heat is fully absorbed by the water, and finally the hot water or water vapor is collected to extract heat energy.
This is the most popular mining method at present, but there are also certain drawbacks, that is, we cannot accurately control the direction and extent of the widening of the formation fissures for the time being. In this kind of engineering, the error is very fatal, in addition to the inability to achieve the purpose of extracting thermal energy, there may be results that we cannot predict.
Moreover, the expansion of stratigraphic fissures is accompanied by an increase in the risk of earthquakes. If the thermal energy is not exploited, and the area becomes an "artificial seismic belt", it will not be worth the loss.
< h1 class="pgc-h-arrow-right" data-track="37" > more than one country </h1>
In 1973, the United Kingdom also began to develop research on hot dry rock resources, which was named the Rosmanus Project because it was carried out in the area of Rosmanus Volcano.
In 1977, the UK launched the second largest hot dry rock project in history, but this time the UK only detected a depth of 2600 meters, and the measured temperature was 100 degrees Celsius.
In 2009, the project was also sponsored by the European Union. At present, the United Kingdom also plans to develop and utilize a geothermal resource located 4 kilometers underground, and once the power station is completed, it can provide one-tenth of the uk's electricity consumption.
In 1987, France, Germany and the United Kingdom cooperated in experimental research related to hot dry rock, and in the process of constantly exploring the mining technology of hot dry rock, it has now matured. In 1997, the International Energy Agency developed a four-year Hot Dry Rock Action Plan, which was joined by Australia, Japan and Sweden in addition to the United States, Germany and the United Kingdom.
Among them, Australia is the country that started the hot dry rock research the latest. In 2003, Australia was developing a hot dry rock project in the Cooper Basin, and according to the website of the Australian company at the time, the reserves of geothermal resources below this basin were equivalent to 50 billion barrels of oil. Australia drilled the well to a depth of 4500 meters and measured a temperature of 270 degrees Celsius.
The first to achieve stable power generation from hot dry rock was the Soultz power station in France, a geothermal research project in 1987 in cooperation between Germany and France.
After more than 30 years of continuous research and attempts, the technology of converting hot dry rock energy into electrical energy has finally been developed, which is a major breakthrough in geothermal energy research, so even if the return on investment of this power station is not high, it still enjoys a high reputation in the international scientific community.
<h1 class="pgc-h-arrow-right" data-track="45" > China's research and exploration of hot dry rocks </h1>
China's research on hot dry rock started slightly earlier than Australia, but in the early stage of research, it did not develop rapidly in Australia.
In 1993, China and Japan carried out a two-year cooperation in Fangshan District, Beijing, focusing on the experimental projects related to hot dry rock power generation. Since then, the Chinese team has begun to understand the mining technology of various hot dry rocks and independently studied related development issues.
Tips: With the sustained and rapid growth of China's economy, in order to cope with the energy crisis and promote the development of Renewable Energy in China, the exploration, development and utilization of geothermal resources have once again attracted the attention of relevant state departments, and some national geothermal resources survey and evaluation projects have been launched, and the development and utilization of geothermal resources is about to set off a new round of upsurge。
In 2007, the Geothermal Committee of the China Energy Research Association and the Australian company also cooperated for two years. During this period, experts from the two countries came to the area that may be rich in hot dry rock resources to investigate and analyze and test the collected samples.
It was found that the distribution area of geothermal resources in Daqing City reached 5,000 square kilometers, and these geothermal resources were 10,000 times the oil and gas energy of the city at that time.
Tips: The hot dry rock research project lasted for three years and achieved certain results in exploring resources, simulating experiments, designing power generation systems, and material applications.
In 2012, the National High-tech Research and Development Program deployed four topics for the hot dry rock research project, which were issued to four universities in China, of which Jilin University was the leading unit of the project.
The first time China drilled wells to obtain superior quality hot dry rock was in 2014. At that time, experts inferd that there were a large number of hot dry rock resources in the north-central part of the Qinghai Gonghe Basin through research and analysis of various geological data, supplemented by a variety of survey techniques.
The reconnaissance well in the Republic Basin began in June 2013, and after 10 months of effort, hot dry rock was drilled for the first time at 2230 meters underground, where the temperature of hot dry rock was only 153 degrees Celsius. It wasn't until about three years later that the team drilled hot dry rocks with temperatures of up to 236 degrees Celsius at 3,705 meters underground, breaking the record for the highest temperature of hot dry rocks previously surveyed.
Tips: Hot dry rock power generation technology can greatly reduce the impact of greenhouse effects and acid rain on the environment, and is not constrained by seasons and climate, and the cost of using hot dry rock power generation is only half of wind power generation and only one-tenth of solar power.
In the Qinghai Gonghe Basin, the distribution range of hot dry rocks reaches 230 square kilometers, and the hot dry rocks between 2.1 km and 6 km underground weigh nearly 4.5 billion tons after energy conversion into standard coal. Experts pointed out that the discovery in the Qinghai Republican Basin is a driving force to promote the research of hot dry rock in China to a new level.
In 2019, China found a large number of hot dry rock resources in Rizhao, Weihai and other places in Shandong, equivalent to more than 18.7 billion tons of standard coal. In the same year, Chinese scientists went to France and Italy for academic exchanges, inspected geothermal power stations, and absorbed and learned experience and advanced technologies in hot dry rock power generation.
<h1 class="pgc-h-arrow-right" data-track="56" > conclusion </h1>
Nowadays, China's hot dry rock research industry is still developing, I believe that in the future, we will be able to overcome technical difficulties, achieve efficient use of hot dry rock resources, and solve energy problems in the country and even the world.