Causes analysis of well collapse and understanding of drilling fluid in Jin58 well area of Dongsheng gas field

In view of the wellbore instability in the drilling construction of Jin58 well area, based on the analysis of formation lithology and clay mineral composition, the main causes of wellbore instability are explained. According to the construction difficulties, the drilling fluid node control is strengthened, the drilling fluid performance index is optimized, the drilling fluid countermeasures to prevent well leakage and well collapse are put forward, and a relatively complete drilling fluid technology is formed. The field application of JPH-438 well shows that the strong inhibition and sealing property of drilling fluid are beneficial to wellbore stability. Density is the key to prevent anti-collapse. The drilling fluid of this well has stable performance, good lubricity and regular well bore. The greatly reduced hole diameter enlargement ratio can effectively prevent well leakage and well collapse, achieving effective drilling and good application effect.