中文
China is a coal rich country with abundant and widely distributed coal,rock,and gas resources,and enormous potential for exploration and development.However,it has always been regarded as a forbidden zone for exploration and development.
According to Li Guoxin,due to the limitations of traditional coalbed methane geological theory,traditional coalbed methane mainly exists in the coal matrix in an adsorbed state under groundwater pressure sealing.As the burial depth increases and the formation temperature rises,the adsorption capacity of coal matrix for methane decreases.Therefore,traditional theory suggests that the main development depth of coalbed methane is 300-1200 meters.When the burial depth exceeds 1500 meters,the gas content is low and the development cost increases,so it is called a restricted area
With the deepening of exploration and development practices,the industrial and academic communities have discovered significant differences between coal rock gas and traditional coalbed methane.The gas produced by”gas loving”coal has characteristics such as a high proportion of free gas,micro migration,free gas dominance in the early stages of production,and adsorption gas substitution.It is a new type of unconventional natural gas that falls between conventional gas and coalbed methane.
Coalbed methane is buried relatively shallowly,and sometimes due to the influence of fracture damage,its sealed layer is like a pot lid being opened when cooking,and a large amount of gas is lost.Only some adsorbed gas exists in the middle of the meal,which is difficult to extract.Coal rock gas is the’storage’environment of coal rock gas inside the pot when the pot lid is intact and not opened.”Li Guoxin further compared it.
“Although this new type of coalbed methane and traditional coalbed methane both use coal as the reservoir,they are very different in geological and development characteristics.Traditional coalbed methane requires long-term drainage and depressurization to produce gas,and the production is low.”Zhang Shuichang,an academician of the CAS Member,said,”Compared with traditional coalbed methane,the coalbed methane reservoir has a deeper burial depth and better preservation conditions.The coalbed methane with a burial depth of more than 2000 meters has the characteristics of high pressure,high temperature,high gas content,high saturation,and high migration.”
Overall,the coal and rock gas reserves are more optimistic.Currently,the annual gas production is equivalent to the scale of two million tons of oil fields,and the future is promising,”said Li Guoxin.