Well wall collapse pressure calculation method considering under-balanced drilling of infilled well

The invention discloses a method for calculating under-balanced drilling well wall collapse pressure in consideration of an infilled well. Comprising the following steps: establishing a three-dimensional geomechanical model and loading a prefabricated well track, collecting a reservoir core to carry out a mechanical experiment and obtain key mechanical parameters, establishing a seepage mathematical equation under the unbalanced drilling condition of the infilled well and setting boundary conditions, and obtaining a dynamic geomechanical field. Stress data under the condition of a prefabricated well track are collected, rock mechanical parameters are updated, and collapse pressure of the infilled well is solved; according to the method, the phenomenon that water invasion is induced by capillary action and chemical potential action under the unbalanced condition is considered, the influence of pore pressure field distribution on stratum stress redistribution under different drilling condition loading is compre