In order to illustrate the influences of the in-situ stress heterogeneity and cleat angle on wellbore stability of coal seam

the following researches have been done. The basic physical properties

mechanical parameters

macro and micro structure of cleats and in-situ stress states of coal and rock in an area have been acquired. Based on the discrete element numerical simulation method

comprehensive evaluation and analysis of the in-situ stress heterogeneity and cleat angles on wellbore stability in coal seam has been conducted by two kinds of evaluation method i.e. the maximal displacement and normalized the plastic area radius. The results of the numerical simulation show that under the condition of isotropic in-situ stress

cleat angle has little influence on the borehole stability. With the increases of the heterogeneity of in-situ stress

the influence of cleat angle on borehole stability is becoming more and more obvious. The maximum displacement around the well increases first and then decreases with the increase of the cleat angle from 0° to 90°. Meanwhile

with the increase of in-situ stress heterogeneity

the anisotropy of the radius of the circumferential plastic area caused by the change of cleat angle becomes more obvious. Therefore

the influence of cleat angle on wellbore stability should not be ignored in coal and rock strata with great difference in in-situ stress. The research results can provide reference for the drilling plan design of vertical and horizontal wells of coal seam in the study area.