塔里木盆地中4井钻具损伤分析

中4井是塔里木盆地卡塔克隆起卡4区块的一口重点预探直井，完钻井深7220m。该井钻井过程中钻具失效严重，失效形式主要有钻具断裂、钻杆二台阶、钻具腐蚀等。从钻具的材质、井下施工条件、地层流体等方面分析了钻具失效的原因：热处理不当造成钻杆接头横向材料冲击功较低，导致加重钻杆接头纵向开裂；蹩跳钻加快了钻具疲劳裂纹的萌生与扩展，扭矩过大致使钻杆在井下产生二次上扣现象，井底与地面的温差大，使原合适的扭矩变大，还有螺纹扣底部没有应力减轻槽，导致钻铤和钻杆断裂；地层流体矿化度高，存在较高质量浓度的Cl^-、SO4^2-，地层中存在CO2、H2S等腐蚀性气体，导致钻具严重腐蚀。对塔里木盆地以后超深井钻井时的钻具使用提出了建议。

Analyses of Drilling Tools' Damages During Drilling Zhong 4 Well in Tarim Basin

Zhong 4 Well, completed at the depth of 7220m, is a key vertical exploration well in the Katakelongqika-4 block in Tarim Basin. Severe drilling tools failures such as drilling tools twisting off, drillpipe wear, and drill-tool corrosion happened during drilling this well. Causes resulting in drilling tools' failures are analyzed in terms of tool materials, downhole operating conditions, formation fluids, etc. Improper heat treatments lead to lower radial concussion power of drill pipe connections, e. g. axial cracks of HWDP connections. Bit bounces quicken drilling tools' fatigue fracture development and expansion. Excessive torques lead to down-hole secondary making up. Initial torques get larger due to bigger temperature differences between surface and bottom hole. There is no stress mitigation slot at the bottom of threads which results in drill collars and drill pipes twist off. High formation fluids mineralization such as Cl- and SO42- and corrosive gases presented in formation lead to severe drilling tools' corrosion. Finally the paper gives suggestions for properly using drilling tools while drilling ultra-deep wells in Tarim Basin in the future.