Research on the comprehensive development mode of coal and coalbed methane

I. Foreign coal bed methane development mode

(1) Underground coal mine extraction mode. Britain, Germany and other Western European countries coal bed methane resources are small, tons of coal with low gas content, is not suitable for ground development of coal bed methane, coal bed methane development is mainly used in coal mining underground pumping and closed pumping in the air-sealed area, no ground development.

(2) Ground development mode. The United States, Canada and Australia are rich in CBM resources, with high gas content in tons of coal and development of primary coal, mainly adopting the ground CBM mining mode. 2008, the United States produced about 557×108m3 of CBM in ground development, and pumped 60×108m3 in wells; the annual output of CBM in ground development in Australia was 36×108m3, and pumped 10×108m3 in wells; and the ground development in Canada produced 86×108m3, with the annual output of 86×108m3, and pumped 10×108m3 in wells. The annual production of coalbed methane in Australia is 36×108m3, and underground extraction is 10×108m3; the annual production of coalbed methane in Canada is 86×108m3, and underground extraction is 6×108m3.

The second is the concept of China's development mode of gas mining before coal mining

(a) The current mode of development of coal and coalbed methane can't eliminate the gas disaster fundamentally

Coalbed methane is the main culprit of the protruding and exploding of gas in coal mines, and the deaths of the people who died in the coal mine accidents in the country in the recent decade are mostly more than 5,000 people. In the past 10 years, the number of people killed in coal mine safety accidents each year in China has been over 5,000, accounting for 80% of the death toll in the global coal industry, of which the deaths caused by gas disasters are generally over 2,000, and although it has declined in the past two years, it is still much higher than the world average.

For a long time, the coal mine drainage work is mainly taken by the "extraction while digging, extraction while mining, extraction and discharge after mining" and other methods of management of gas, gas extraction in the coal mine mining, digging and carry out, the danger is very great, the vicious gas explosion accidents are difficult to put an end to at all, and at the same time lead to the mine of coalbed methane gas extraction rate is low and low concentration of gas extraction, utilization rate is low.

Practice has proved that the traditional gas management can not fundamentally eliminate gas disasters, with the increasingly mature coalbed methane ground development technology, making it possible to develop coalbed methane through ground drilling, through the ground and underground mining, different phases have their own focus, to maximize the reduction of gas content in coal mines, and fundamentally eliminate coal mine safety accidents, maximize the use of resources, protect the environment, can receive a good safety effect, can also be used to protect the environment, can receive a good safety effect, can also be used to protect the environment.

With the rapid development of coalbed methane industry, there are two misunderstandings in the development and utilization of coalbed methane: one is that coal mining enterprises treat coalbed methane as a hazardous gas, and the extraction of coalbed methane is to ensure the safety of coal mine production, ignoring the huge resource effect, environmental effect and social effect of coalbed methane. Secondly, the development of CBM in recent years has not taken into account the impact on subsequent coal mining, which will bring potential safety hazards to subsequent coal mining. Therefore, how to rationalize the coordinated relationship between coal production and CBM development and utilization, and establish a CBM development mode combining underground extraction and surface development, so that the coal industry and CBM industry can be coordinated and orderly development is an urgent problem in front of us.

(2) China should take the CBM development mode combining underground extraction and surface development

The development of China's CBM industry should learn from the successful experience of North America's surface development of CBM and Western Europe's underground extraction of CBM in coal mining areas, and based on the geologic features of CBM and the degree of coal mining in different regions, take the road combining surface development of CBM and underground extraction, which is the best way to realize the comprehensive development of China's coal and CBM. It is an effective way to realize the comprehensive development and utilization of coal and CBM in China.

Therefore, the comprehensive development of China's coalbed methane and coal should follow the principles: First, different geological conditions are treated differently, and different mining methods are adopted, not one size fits all. Secondly, the coal mine production area and coal mine planning area are treated differently, the coal mine production area is mainly to protect the safety, under the premise of ensuring the safe production of coal as far as possible to develop and utilize the coal bed methane; the coal mine planning area is strictly in accordance with the first gas mining and then coal mining development procedures.

1. Different geological conditions are treated differently, and different mining methods are adopted

Coalbed methane in China has complex geological conditions, and the difficulty of development varies greatly. In areas where the geological conditions are simple and the coal structure is well preserved, it is easier to develop coalbed methane on the ground; while in areas where the tectonic conditions are complex and the coal structure is seriously damaged, it is more difficult to develop coalbed methane on the ground. Therefore, it should be treated differently according to different geological conditions.

For gas-bearing areas where the gas content of tons of coal is higher than 6m3/t and the structure of coal body is well preserved and the primary structural coal is developed, the gas should be extracted first and then the coal should be extracted; and for tectonic coal development areas where the structure of coal body is poorly preserved and low-gas-bearing areas, the main focus should be on downhole pumping, which should be done first and then the coal should be extracted.

2. The gas content of tons of coal is higher than 6m3/t and the primary structural coal development of coal mine production area and planning area are treated differently

Coal production area: the main focus is to ensure the safety of coal production, as far as possible under the premise of ensuring the safe production of coal development and utilization of coalbed methane, if the safety of production can not be guaranteed, should unconditionally stop coal mining, the use of ground drilling and downhole pre-mining pumping methods to reduce the gas content of coal seams, so that the coalbed gas content can be reduced to a certain level. Reduce the gas content of coal beds to meet safety standards before coal mining.

Coal planning area: for the gas content greater than 6m3/t of primary structural coal development of coal planning area, should be strictly in accordance with the first ground gas mining and then underground coal mining development procedures, namely: ① use the protection of coal seams of the ground drilling and completion of the wells of the measures to increase production, pre-pumping of coal bed methane of the original seams; ② mining period of mining, the use of mining work of the overpressure, mining pressure, downhole coal bed methane extraction; ③ The coal bed methane extraction in the air-mining area and abandoned mines, after the main coal seam is mined, the unloading of pressure is more adequate, and the coal bed methane is extracted through the surface drilling, buried pipe and roadway; ④ the recycling of coal bed methane for mine ventilation (Figure 5-18).

Figure 5-18 Schematic flow chart of China's CBM development model