Velocity sensitivity and its influencing factors of high-rank coal reservoirs in southern Qinshui basin

The result of sensitivity evaluation experiment for flow velocity of gas flowing through coal is used for determining a reasonable recovering rate of coal bed gas reservoir, which is of great significance for CBM development. Because of low porosity and low permeability of the high rank coal reservoir, the velocity sensitivity evaluation of the high-rank coal reservoir can not follow the liquid experimental methods of conventional reservoir. Therefore, this paper put forward a new method of sensitivity evaluation of high rank coal reservoir by using the nitrogen, and conducted the flow sensitivity test on samples of high rank coal in southern Qinshui basin. The results show that high rank coal has low velocity-sensitive damage rate in Southern Qinshui basin, the damage rate ranges mainly from non to weak and weak medium. Original permeability is the main control factors of velocity-sensitive damage for high rank coal reservoir, the higher the coal reservoir permeability, the higher the velocity-sensitive damage rate. The clay content in coal reservoir has limited influence on velocity sensitivity, the velocity-sensitive damage rate is mainly associated with the mode of occurrence of clay mineral in coal. When the clay minerals occur mainly in coal fracture, the velocity-sensitive damage rate is relatively large for high rank coal.