Comparison of main differences and similarities between CBM and conventional natural gas

The CBM industry is a rising industry that has emerged in the world for more than two decades. CBM is a type of methane gas that is mainly adsorbed and is generated and stored in the coal seam and its surrounding rocks. Its calorific value is greater than 8,100 kcal/m3, which is similar to the conventional natural gas as follows:

1, the same point 1 gas composition is roughly the same:

The CBM is mainly composed of more than 95% of methane, and the other 5% of the gas is generally CO2 or nitrogen; and the natural gas composition is also mainly methane, and the remaining components vary greatly.

2 uses the same:

Both gases are high quality energy and chemical raw materials that can be mixed and mixed.

2. Different points 1 The coal bed methane gas basically does not contain heavy hydrocarbons with carbon number 2 or higher, and the output does not contain inorganic impurities. Natural gas generally contains heavy hydrocarbons containing more than two carbons, and contains inorganic impurities when it is produced. 2 Different ways exist in the underground. Coalbed methane is mainly present in coal seams in the form of adsorption of macromolecules, while natural gas exists mainly in free gas in sandstone or limestone. 3 Production methods and yield curves are different. CBM is used to reduce formation pressure through drainage, so that coalbed methane is desorption-diffusion-flow in the coal seam to produce ground, while natural gas is mainly produced by its own positive pressure; the initial production of coalbed methane is low, but the production cycle is long, up to 20 -30 years, natural gas production is high in the initial period, and the production cycle is generally about 8 years. 4 Coalbed methane, also known as coal mines, is the main safety factor for coal mine production. At the same time, coalbed methane resources are directly related to coal mining. If gas production was not used before, coal-bed methane was released into the atmosphere during coal mining. According to relevant statistics, China's coal resources are reduced by more than 19 billion m3 per year, while natural gas resources are less affected by other mining activities. Can be controlled programmatically. The table is summarized as follows:
Various conventional gas reservoirs CBM reservoirs 1. The buried depth is deep and shallow, generally greater than 1500 meters and less than 1500 meters. 2. The resource calculation is unreliable and reliable. 3. The exploration, development and development mode. Rolling exploration and development or exploration and development after the first Exploration and development 4. Traps of gas storage methods, free gas is adsorbed in the coal formation (most of them) 5, gas components are hydrocarbon gases, mainly C 1 - C 4 95% or more is methane 6, and the pore structure of the reservoir is mostly Single pore structure, double pore structure, development of micropores and fissures 7, high permeation permeability, low sensitivity to stress, low permeability, sensitive to stress, 8 large-area contiguous mining within the scope of trapping. With large well spacing, single wells can be used, usually with a small number of production wells to be mined, well networks must be used, the number of wells is more than 10, reservoir pressure is overpressure or underpressure at normal pressure, or atmospheric pressure is 11, the production mechanism is gas in nature Seepage to the wellbore under pressure, wellhead pressure requires drainage and pressure reduction, gas desorption after pressure drop, diffusion in the pores, and then seepage through the fracture to the wellbore 12, the initial single well output high and low yield increase measures generally do not need 14 Drill And the production process is relatively simple and more complex, the need to manually upgrade drainage gas.