After coal seam mining,stress change and rock movement in adjacent rock strata, make permeability and other fields change in adjacent coal seam. At the same time, due to the exploitation of coal seams, material exchange may occur in the adjacent coal seams. It also caused desorption of near coal seam near the mining working face. Recent years, with the development of coalbed methane mining technology under pressure relief in mining areas, it is necessary to carry out numerical simulation under coalbed methane mining conditions to realize the optimization of coalbed methane extraction simulation under mining conditions. The coupling effect of dynamic virtual well and variable permeability field advancing with the mining face is used to simulate the output of coalbed methane under mining conditions: the dynamic virtual well is used to advance with the mining face to characterize the influence of the working face on the material exchange of adjacent coal seams in the mining process; the use of variable permeability field to realize the influence of the permeability of the adjacent coal seam during the advancement of the working face. Finally, through the dynamic coupling of variable permeability field and dynamic virtual well with the mining face, the rapid pressure relief effect of high speed and short time on the adjacent layer under the influence of mining is characterized. The simulation results of the computer simulation software written by the algorithm show that when the mining effect is not considered, that is, when the algorithm does not consider the dynamic virtual well production and the variable permeability field, it is basically consistent with the commercial software simulation results, but for the consideration of mining condition is a situation that commercial software cannot simulate, and the simulation results of this algorithm are more consistent with the actual monitoring data of the mine. This method achieves numerical simulation of CBM under mining conditions by improving the mature algorithm, which can provide effective guidance for future CBM capacity prediction under mining conditions.

Weizhou 11-4N oilfield is a medium-low-porosity and low-permeability reservoir. The oilfield was initially developed by edge and bottom water energy and then transferred to water injection development. Affected by poor physical properties and heterogeneity of the reservoir, the oilfield appeared in the process of water injection development. When the water injection pressure increases, the water injection volume continues to decrease, and it is difficult to meet the injection requirements. On the basis of the analysis of reservoir heterogeneity, void structure, and clay minerals of reservoir, the water injection compatibility experiment, damage evaluation experiment, and nuclear magnetic resonance-velocity sensitivity experiments were carried out to clarify the damage in the process of oilfield water flooding development. Experiments show that the main causes of damage in Weizhou 11-4N oilfield water flooding development process are water quality incompatibility and strong velocity-sensitive damage. The determination of water type shows that the injected water and formation water are MgCl2 water type and NaHCO3 water type, respectively, under the classification of Surin water type, resulting in the formation of scale with calcium carbonate as the main component in the reservoir. Incompatibility of water quality is an important cause of reservoir damage and scaling. In the reservoir-sensitive flow experiment, the experimental core showed strong velocity sensitivity, the average velocity sensitivity damage rate was 466.31%, and the average critical velocity was 2.98 m/d. Nuclear magnetic resonance experiments show that the core has a significant decrease in average pore size after water flooding. The main damage range is the tiny throat of 0-2 μm. In this paper, the main damage interval of velocity-sensitive damage in the Weizhou 11-4N area and the change trend of void structure after velocity-sensitive experiment are clarified by nuclear magnetic resonance and velocity sensitivity experiments. The main cause of block reservoir damage provides the basis for the oilfield to take targeted measures and provides a guarantee for the efficient development of the subsequent oilfield.