Maintaining wellborestabilityinunconventionalgas wellsis muchimportanttotheexplorationand productionofnaturalgasincoalＧbearingformationinthesouthwesternregionofGuizhouProvince．Thispaper investigatesthewellborefailuremechanismincoalandmudshaleformation,andfindsoutthatthetwokindsof wellborefailuremechanismsareessentiallydifferent．Inaddition,solutionsforwellboreinstabilityareinvestigated intermsofchemistry,mechanicsand mechanicscoupled withchemistry．Influenceof wellboreinstabilityon wellＧradiusvariationsandcorerecoveryisanalyzedinthecontextofaCBM wellinZhinaCoalfield,leadingtothe findingthatwellboreenlargementisgreaterwithlowercorerecoveryoverthecoalＧmudstonesection．Predicting accuratelytheformationpressuresofexploration wells,optimizingthedrillingfluidsystem anddensity,and choosingtherightdrillingtechniquescontributetoCBM wellborestabilityinthesouthwesternregionofGuizhou Province．