Study On N₂ Displacement Of CBM Well In Luan Mining Area

With the rapid development of China's economy,the gap between supply and demand of natural gas continues to increase,and the development of CBM is paid more and more attention.The CBM resources are abundant,gas content is large,and the threat of gas disaster is becoming more and more serious with increasing mining depth,Therefore,development of CBM in luan mining area is great significance.However,it is difficult to increase production of low-yield and capability reduced well,because low-permeability/pressure and low diffusive characteristics of the coal reservoir.Based on the coal reservoir characteristics and gas phase displacement technical principle,analysis and research the conditions of N₂ displacement by laboratory experiment and numerical simulation.?1?Ssingle component isothermal adsorption experiment.The Langmuir volume CO₂>CH₄>N₂,respectively 41.60m³/t,29.38m³/t and 21.72m³/t.?2?Langmuir pressure CO₂<CH₄<N₂,respectively 0.73MPa,1.27MPa and3.52MPa,N₂ has strongest ability of reduce-pressure and desorption,and the CH₄ is second,CO₂ is weakest.?3?N₂ displacement CH₄ experiment.The permeability change was:early rapid increase-middle period slowly increased-latter basically stable;and permeability increased from 0.0053489mD to 0.0063534mD,with an increase of 19%.The percentage of N₂ was increased and CH₄ decreased.?4?The change rule of gas and water for producing Wells in N₂ displacement process:gas production in early rapid decline-middle rising fast-late steady decline,water production early rising fast-middle rapid decline-late basically stable.?5?Established numerical model by COMENT3 numerical simulation software,Analysised relationship between the displacement effects and production injection well spacing,drainage time,N₂ injection pressure,N₂ injection mode and water saturation,and optimize the N₂ displacement scheme,the scheme net increasing CH₄production 547,000m³ and N₂ injection 1,391,000m³ in 10 years for single well,1m³ N₂ replacement 0.40m³ CH₄,replacement ratio of 1:0.40.