Analysis of Drainage and Depressurization Model and Drainage Laws of CBM Well Based on Seepage Mechanics

The reservoir pressure drop funnel calculation model for single well and group wells is established, and the reservoir pressure drop propagation law of 10 CBM wells in 4 moments is simulated in southern block of Shizhuang by Matlab software, it is found that the shape can be divided into two categories by observing the dynamic drawing of 10 wells: one is that the velocity of lateral expansion of the pressure drop funnel is slow, and the velocity of longitudinal expansion is fast, such a shape leads to larger reservoir pressure drop; the other one is that the velocity of lateral expansion of the pressure drop funnel is fast, and the velocity of the longitudinal expansion is slow, the coal reservoir pressure is not obvious far away from the wellbore area, and increases rapidly in the near wellbore area. In the case of group wells production, the phenomenon of inter well interference can increase the total production of coalbed methane and increase the gas production rate. Meanwhile, the interwell interference shows a certain direction along the direction of the principal stress.