尼日利亚A区块Kukaku-1井卡钻事故的处理

Kukaku-1井是尼日利亚A区块的第一口探井，该井地质情况复杂，在阿格巴达组存在着高压层。钻进中在?311.1 mm井眼中提前钻遇高压层并发生井涌，压井液密度和漏失密度窗口太窄导致压井中发生井漏，堵漏过程中由于堵漏浆与材料储备不足，采用海水循环后导致井壁垮塌而造成卡钻。处理卡钻事故中由于井壁垮塌程度加剧、卡点不断上移并最终埋掉了几乎所有裸眼井段的钻具，通过三次切割钻具后起出部分钻具，最终该井眼报废，填井侧钻。该事故处理过程中的经验和教训对该区块后续钻井的顺利施工具有重要借鉴意义。

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.