Abstract: Wellbore collapse in the carbargilite section in Changqing gas field has resulted in frequent occurrence of downhole troubles and sidetracking. To resolve these problems, rock samples taken from the carbargilite formation were studied for the microstructure, cation exchange capacity, mineral composition and physiochemical property. The effect of drilling fluid on the mechanical characteristics and collapse pressure of the rock samples was tested, and the mechanisms in which the carbargilite formation collapses and ideas on which the drilling fluid technology for preventing carbargilite formation collapse was studied were determined. A high performance drilling fluid having strong plugging capacity and high inhibitive capacity was formulated through laboratory experiment. Plugging agents of different hardness and shale inhibitors selected, and nano-emulsion were used to render the drilling fluid properties required. The HTHP filter loss and API filter loss are ≤ 6 mL and ≤ 2 mL, respectively. Rate of sandstone (Shihezi formation) plugged by the drilling fluid is ≥ 85%. Rate of linear swelling of artificial rock cores is reduced by at least 60%. Field application of the drilling fluid on 18 wells in Changqing gas field showed that the percentage of sidetracking when drilling the carbargilite formation was reduced to 16.7%. Average drilling time was reduced by 30 d. The use of this drilling fluid has achieved the desired effect, and satisfied the needs of safely drilling the carbargilite formation in Changqing gas field.