Karst caves in the shallow fracture zone in Sichuan and Chongqing are developed. The problem of leakage and collapse is widespread，which seriously affects the ROP. In view of the problems that the traditional cement plug is difficult to stay and the karst cave is difficult to plug, an ultra low density foam cement slurry quick drying plugging system has been developed, with a density range of 0.7～1.0 g/cm3, the thickening time is adjustable, and the 24 h plugging strength is higher than 2 MPa. The technology of nitrogen?foam??plugging has been successfully applied in five wells, and the plugging success rate was 100%.It not only improves the filling effect of Karst cave, but also consolidates the well wall. The major technical problems of leakage, collapse and collapse were solved at one time. The surface drilling period was shortened by 72%, ensuring the follow-up excellent and fast drilling, and providing a technical reference for the treatment of leakage and collapse in the shallow fracture zone.