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Do you know? Why is coalbed methane called "sweet gas"?
Coalbed methane, also known as coalbed natural gas, refers to natural gas extracted from coal seams. In recent decades, it has become an important energy source in the United States, Canada, Australia and other countries. The characteristic of coalbed methane is that its main component is methane and it is called "sweet gas" because it does not contain hydrogen sulfide. This characteristic makes coalbed methane more attractive in the market, especially today with increasing energy demand.
Coalbed methane is formed by the adsorption of methane inside coal seams. Compared with traditional sandstone or other conventional natural gas reservoirs, coalbed methane has a unique storage method. It mainly stores methane in coal through the adsorption process.
How is coalbed methane formed? With the thermal maturation process of organic matter and solid hydrocarbons, coalbed methane gradually forms in coal. This natural process gives coalbed methane its special chemical properties, including a lower proportion of heavier hydrocarbons than those found in conventional natural gas.
The history of coal bed methane
The discovery of coal seam methane mainly stems from the ventilation of coal seams. As early as centuries ago, the methane in coal seams was known to miners, so holes were usually drilled before mining to allow the methane to escape to ensure safety. In the late 1970s, coalbed methane began to gain greater attention as a natural gas resource as the U.S. government supported research into non-traditional natural gas sources.
Coalbed methane extraction technology continues to advance, making it one of the most important sources of energy, especially in countries with increasing energy demand.
In Australia, commercial coal seam methane mining began in Queensland in 1996. Coal seam methane resources here now account for about 10% of Australia's natural gas production.
Reservoir characteristics of coalbed methane
The reserve distribution of coalbed methane is related to many factors, including its porosity and adsorption capacity. Coalbed methane reservoirs are mostly dual-porosity reservoirs, which means that the natural fractures of coal (called clear fractures) have an impact on the flow behavior of gas, while its internal structure is mainly responsible for the storage of its gas. In addition, the type and quality of coal also directly affects its gas adsorption capacity, which usually ranges from 100 to 800 standard cubic feet/ton of coal.
Extraction process
The coalbed methane extraction process requires drilling 100 to 1,500 meters underground. As the pressure in the coal seam drops, gases and produced water rise through pipes to the surface. Depending on the geological conditions, the quality of produced water will vary and it may contain undesirable chemicals. The coalbed methane production process also typically involves significant initial investment, but the returns are relatively substantial.
Production data show that the production curve of a coalbed methane well will show a "negative attenuation" characteristic, that is, when water is pumped out, the gas production rate will gradually increase.
Environmental impact
Although coalbed methane is a relatively clean natural gas, its extraction process still has environmental impacts, especially in terms of emissions and water resources. Since methane has a greater impact on global warming than carbon dioxide, its release cannot be ignored. Studies in some areas have pointed out that the extraction of coalbed methane may affect the distribution of groundwater resources and even cause geological problems.
In addition, many studies have also shown that coalbed methane mining will lead to a decline in water quality, so it is particularly important to take effective water treatment measures. Some companies are implementing harmful gas emission reduction plans and are committed to reducing the environmental impact of mining activities.
If you have more questions about the extraction and utilization of coalbed methane, would you like to learn more about its environmental impact and energy potential?
