Coal occupies such a "prominent" position in the energy structure and should be loved by people. However, for a long time, oil explorers have been very annoyed with coal seams or coal-bearing strata encountered in oil and gas exploration. This is because for a long time, people have always thought that coal and oil are a pair of opposing "enemies", that is, the coal-forming environment is not suitable for generating oil. Therefore, once oil exploration workers confirm that the sedimentary basin they are engaged in is a coal-bearing basin, or that an exploration series belongs to a coal-bearing series, oil exploration often ends or slows down.
In fact, in a large number of domestic and foreign documents, it has been recorded that a small amount of oil was discovered during coal mining. However, these phenomena have not attracted the attention of petroleum geology. The idea that coal-bearing basins or coal-bearing strata are out of touch with oil has bound the thoughts of several generations of petroleum geologists.
People's understanding of nature is endless. In the 1960s and 1980s, with the efforts of several generations of petroleum and geological workers, typical oil fields formed by coal seams or coal-bearing strata were finally discovered in Australia, New Zealand, Canada, Indonesia and other countries.
Why coal can form oil has not been paid attention to by petroleum geologists before? Theoretically, oil is mainly formed by geochemistry, biochemistry and thermal metamorphism of lower organisms (including phytoplankton (algae) and zooplankton) in water. Coal is mainly formed by coalification of terrestrial higher plants. In essence, the "parent materials" of both are biological organic matter, which can be called "homology". So, what is the relationship between coal and oil?
Under the microscope, three basic organic components in coal can be identified: vitrinite (mainly from lignin and cellulose of plants), flint (carbon-rich component formed by silk carbonization of plant tissues) and chitin (hydrogen-rich component composed of plant spores, pollen, cuticle, cork and matrix vitrinite). Vitrinite and chitin are the main oil-generating substances.
Through simulation experiments, scientific and technical personnel found that the higher plant cork mainly existing in bark and humus mainly formed by higher plant lignocellulose can form oil and natural gas under the condition of low temperature and pressure (called "low maturity stage" in petroleum geology), which is the main oil and gas generation stage in the stratum. However, some components in coal can only generate oil when the temperature and pressure are further increased. Under the fluorescence microscope, coal does form petroleum, and many substances with strong fluorescence can be seen in the cracks and holes of the coal block, which is the heavy asphalt left after the coal discharges light liquid hydrocarbons. This phenomenon proves that coal not only generates oil, but also discharges from the coal seam. Many years' petroleum geology and coal petrology research show that if the content of cork in coal reaches more than 3%, it can become an oil source rock with oil generation ability.
Because coal-derived oil has obvious physical and geochemical characteristics, it is easy to be identified. After coal generates oil, the heavy part is often trapped in coal because of the strong adsorption force generated by holes in coal, while the light part is relatively easy to be discharged, so the oil formed by coal or coal-bearing strata is mostly high-grade light oil.
However, due to the strong adsorption of coal and the existence of a large number of micropores in coal, the oil generated in coal is more difficult to discharge than that generated in rocks, which is one of the main reasons why there are countless coal mines in the world, but few coal-based oil fields.
China is extremely rich in coal reserves, and its coal output ranks first in the world for many years. According to incomplete statistics, the distribution area of Carboniferous-Permian, Jurassic and Paleogene coal-producing strata in China accounts for 1/8 of China's land area. Turpan-Hami Oilfield, the third largest oilfield in Xinjiang discovered in Turpan-Hami Basin in recent years, is an example of oil generation and reservoir formation in coal-bearing strata.
Coal can not only produce oil, but also produce abundant natural gas. Because of the strong adhesion of methane molecules, the pore volume in coal is huge. Compared with conventional sandstone reservoirs, the gas storage capacity of coal is greater, which can often reach more than twice that of sandstone reservoirs.
According to the calculation of more than 200 coal-bearing basins with different types and areas discovered in China, the coal resources buried below 2000 meters can reach 5.0882 trillion tons. If the average gas content per ton of coal is 7. 14 cubic meter, the natural gas resources produced by coal can reach 33.6 trillion cubic meters, which is about 65.438+0.596 billion tons of recoverable crude oil.
Of course, among the researchers at home and abroad, some people hold a categorically negative attitude towards coal-to-oil China's petroleum geology generally believes that coal can generate oil, but to form a large-scale oil reservoir with industrial significance, the main contributor should be argillaceous rocks rich in organic matter sandwiched between coal seams, that is, coal-bearing rock series.
Can humans make oil?
The answer to this question is yes. Moreover, the research on artificial (synthetic) oil is almost carried out at the same time as the industrial development of natural oil. Since the beginning of the 20th century, on the one hand, human beings have been increasingly strengthening the exploration and exploitation of underground oil, on the other hand, they have been persistently looking for effective methods to manufacture artificial oil. Especially those countries lacking natural oil resources are particularly interested in the research of synthetic oil.
Among the numerous invention patents, German chemist Friedrich? Fischer and Hans? Fischer-Tropsch synthesis method, founded by Tuozai 1923, has stood the test of history and is still a synthetic petroleum method. During World War II, German scientists and technicians used this method to achieve the pioneering work of providing 1 10,000 tons of synthetic oil to fascist Germany every year. This method was introduced to South Africa in 1955. At present, South Africa's synthetic capacity has reached 6.5 million tons/year.
Fischer-Tropsch synthesis is to synthesize hydrocarbons with hydrogen and carbon monoxide (or carbon dioxide) as raw materials and iron as catalyst. Its chemical reaction mechanism is similar to plant photosynthesis, that is, carbon monoxide (or carbon dioxide) catalyzes hydrogenation and reduction polymerization to form organic compounds.
Japan has recently developed a method to convert seawater into oil. The method they invented has seven steps: ① preparing organic carbides containing carbon elements; (2) preparing carbide (binary compound formed by combining carbon with metal elements with lower electronegativity than itself); (3) manufacturing organic carbon substances; (4) manufacturing organic lead substances (organic carbon compounds containing lead); ⑤ Artificial petroleum raw materials; ⑥ Natural artificial petroleum raw materials; ⑦ Purify artificial petroleum products.
The advantages of this method are low price and rich raw materials. The prepared oil is suitable for automobile engines and the like. Undoubtedly, this method is of great significance.
Not long ago, Bater Laboratory in the Pacific Northwest of the United States proposed a simple method to extract oil from sludge. They first concentrated the sludge in sewers and rivers to reduce its volume by at least 20%. Then a strong alkali is added, and the mixture of sludge and strong alkali is converted into petroleum substances under pressure, and then processed into fuel oil.
The "low temperature conversion method" invented by Canadian and German scientists can also convert sludge into petroleum substances. This manufacturing process can also get 30% concentration of expensive fatty acids. This is a low-cost and environmentally friendly method, which has attracted the attention of industrial departments in many countries. Imagine how exciting it would be if the inexhaustible sludge around the world could be turned into valuable oil after technical treatment!
Modern geochemical research has confirmed that algae is an important substance for oil production, so theoretically algae rich in oil can be used for oil production. Researchers at the American Institute of Solar Energy have successfully developed this technology. The main component of oil produced by this method is gasoline. It converts algae into gasoline and other oils through cracking and casein transfer reaction. This is a relatively expensive oil production technology. It is estimated that at the end of 1990s, the price of gasoline manufactured by this method could reach nearly 500 USD/ton.
Biochemists estimate that each gram of Chlorella can provide 22 kilojoules of energy. Therefore, with the improvement of science, technology and technology, the development and utilization of algae energy has a very broad prospect.
In the vast rural areas, most people directly burn plant cellulose such as wood, vegetation and crop straw, which not only has low calorific value and low utilization rate, but also pollutes the environment. When people try their best to improve the utilization rate of these substances, they find that they can be used to make oil.
In the early 1990s, British scientists converted plant cellulose such as fresh grass into fuel oil through fermentation and some chemical methods. Brazilians get fuel from sugarcane by fermentation, and 65 liters of alcohol and other fuel oil with purity of 96% can be produced from 1 ton sugarcane.
In Maoming, Guangdong Province and Fushun, Northeast China, people have carried out the method of extracting oil from dark brown oil shale rich in organic matter under the condition of high temperature and high pressure catalyst, which should also belong to a method of artificial oil production.
Judging from the methods that have been realized at present, the raw materials for oil production in China are very rich and cheap, and these methods will undoubtedly play an important role in alleviating the energy shortage in China.
In addition, man-made oil also has an important and rich material source-coal. At the high temperature of 400℃ and the atmospheric pressure of 50 ~ 300, coal powder can almost completely become liquid synthetic oil through chemical reaction. This synthetic oil is not much different from natural oil. This proves the possibility of artificial oil in theory and practice.
Many countries attach great importance to producing oil from coal. As early as 1930s, the Soviet Union began to study the hydrogenation of coal, and Soviet scholars also adopted the method of gasifying coal first, and then liquefying coal gas into oil in the presence of catalyst. At the end of 1980s, the cost of synthesizing oil from coal in European countries was 0.5 times higher than that of natural oil at that time, but if the process is improved and production is expanded, the two are expected to be even.
International energy experts believe that the use and consumption of oil by modern large enterprises are increasing, and it should be appropriate to rely on extremely rich coal as raw material to expand liquid fuel production. Some experts even estimate that by the middle of 2 1 century, coal-to-oil may replace natural oil. Of course, the speed of this "replacement" will also depend on the increase of proven oil reserves, the development of modern chemical technology and the changes in the global international political structure.