Disturbed Space Division Of Abandoned Working Face And Evaluation Of Residual Coalbed Methane Resources

The evaluation and development of remaining coalbed methane resources in abandoned working face is of great significance.This thesis takes 12501 working face of abandoned working face in Nanwupan District of Tunlan Mine in Xishan Coalfield of Shanxi Province as the research object.By means of numerical simulation,physical similarity simulation and analysis test,the different zones of abandoned working face are quantitatively divided.The variation characteristics of pore and fissure in coal reservoir under coal seam mining disturbance are studied,and the amount of coalbed methane resources left in 12501 working face is calculated.The main understanding is as follows:Firstly,based on the similar physical simulation results,the height of the caving zone at the bottom of the disturbed rock mining area is 13.24 m after the coal seam excavation of 12501 working face is completed and stabilized.The height of the gas-conducting fracture zone with dense penetration and separation fractures is 46.8m,and the bending subsidence zone extends to 112.5 m from the coal seam roof.Combined with the numerical simulation results,the distribution law of stress field and fracture field in the disturbed area was analyzed,and the remaining coalbed methane occurrence space was considered.Finally,12501 working face was divided into floor fracture zone,recompaction zone,gas conduction fracture zone and pressure bearing zone,and the gas conduction fracture zone was the favorable area for the development of coalbed methane resources.Second,According to the experimental results of NMR,SEM and MIP of coal samples,the compressibility of adsorption pores in confined coal reservoirs is poor,and the compressibility of macropores and microfractures is strong,which provides the main compressed space for the whole sample.After the coal reservoir is compressed until destroyed,the medium-sized pores in the pores and fractures are irreversible compressed due to the plastic change,resulting in the decrease of porosity.However,after the destruction and decompression,it also promotes the increase of cracks and extends through.Third,the calculation results of residual CBM resources show that the CBM resources in the pressure-bearing area are 2.01×10~7m~3;the CBM resources in the floor fissure area are 7.4×10~5m~3;the total amount of CBM resources in the recompacted area is 1.18×10~6m~3;the total amount of coalbed methane resources in the gas flowing fractured zone is 2.68×10~6m~3.The total resources of adsorbed CBM and free CBM in each mining disturbance area of 12501 working face are 2.32×10~7m~3and 1.48×10~6m~3,respectively,with a total of 2.468×10~7m~3.