Handing of pipe stuck in Well Kukaku-1 block A of Nigeria

Well Kukaku-1was located in Block A of Nigeria which was the first exploration well in this block. Geological conditions in Block A were complex with high potential sloughing, mud loss risks. The high pressure section in Agbada formation was a challenge for safe drilling. Well kick was encountered in ?311.1 mm hole section because of the high pressure before the expected depth and hole size. And then severe lost circulation occurred while killing the well due to the narrow gap between kill mud weight and formation loss gradient. Finally, the pipe was stuck resulted from well collapse when replace kill mud with sea water due to the shortage of mud and LCM. Part of the drilling tool was freed after 3 times pipe cutting operation, but still almost total drilling tool in open hole was lost in the hole because of the increase of well collapse degree and upward movement of stuck point during the treatment. The original wellbore was abandoned for sidetrack and huge losses of cost were experienced. Although the treatment of this down hole problem was failure, the experiences and lessons from the treatment process are valuable guides for the future drilling operation in this block.