Abstract: Well KL-2 is a wildcat well drilled in the predmont structure of Kelasu structure in Tarim basin. Complex situations such as undergauge, overflow, lost circulation and differential sticking are easy to occurs when drilling in salt-gypsum layers and overpressured gas layers.These problems are solved through using polysulfonate potassium chloride drilling fluid and keeping drilling fluid density at 1.75 to 1.80g/cm3 in halite intervals and at 2.20 to 2.40 g/cm3 in overpressured gas intervals to balance formation pressure.