Pressure containment lost circulation control technology in long open-hole of upper salt bed formation of well AT22

There is a salt bed in in long open-hole of well AT22, to increase mud weight, control creeping of salt-bed and prevent pipe-stuck, the pressure containment capability of upper formation must be increased. According to the formation characteristics and demand of pressure containment, the open-hole section is divided into five parts, and a series of LCM mud formulations are developed in laboratory. However, after the pressure containment operation, the first time of lost circulation test is failed to meet the demand of bottom equivalent density of 1.73 g/cm3, because drilling fluid density is low (1.45 g/cm3) that the equivalent density at the cashing shoe is much more than the formation breakdown pressure. After pressure containment operation at the formation of casing shoe, the second time of lost circulation test is successful, and the equivalent density at bottom reaches to 1.74 g/cm3 with the drilling fluid density of 1.60 g/cm3, which meets the requirement of improving drilling fluid density to drill salt bed formation safely.