大位移井套管磨损预测及剩余强度计算

Prediction of Casing Wear and Calculation of Residual Strength in Large Displacement Wells

在大位移井钻进过程中,由于水垂比大的特点,钻柱在井下运行形式复杂,造成套管内壁磨损严重,套管强度降低,极大地影响了后续钻井和生产作业。应用基于能量传递的套管磨损效率模型,采取分段法求取管柱侧向力,对套管月牙形磨损进行分析,并依据API(American Petroleum Institute)最小壁厚法,简化月牙状套管磨损,建立套管磨损预测及剩余强度计算方法。利用该模型对南海某大位移井进行计算。结果表明:侧向力是影响套管磨损的主要因素,倒划眼对套管的磨损效果明显强于正常钻进。全井段磨损最严重的位置是狗腿角最大的井段,套管失效的风险最大,是采取防磨措施的关键井段。经计算该井四开作业完成之后,狗腿角最大处的套管磨损深度为1.15 mm,套管强度衰减至原始强度的58.24%,但仍能满足强度要求;该研究成果为南海大位移井套管磨损的防治提供了依据和参考。

During the drilling process of large displacement wells,due to the high horizontal-vertical ratio,the movement of the drill string underground is complex,resulting in severe wear on the casing wall and a reduction in casing strength,greatly affecting subsequent drilling and production operations.A casing wear efficiency model based on energy transfer was applied.The segmented method was used to determine the lateral force on the pipe string,and the crescent-shaped wear of the casing was analyzed.Based on the API(American Petroleum Institute)minimum wall thickness method,the crescent-shaped casing wear was simplified,and a method for predicting casing wear and calculating residual strength was established.Using this model,calculations were performed on a large displacement well in the South China Sea.The results show that lateral force is the main factor affecting casing wear,and reverse circulation drilling has a significantly greater effect on casing wear than normal drilling.The most severely worn section of the entire wellbore is the section with the greatest dogleg severity,where the risk of casing failure is highest,making it the critical section for implementing anti-wear measures.After the completion of the four-stage operation in this well,the depth of casing wear at the location of the maximum dogleg severity is 1.15 mm,and the casing strength has decreased to 58.24%of its original strength,but still meets strength requirements.The research outcome provides a basis and reference for the prevention and control of casing wear in highdisplacement wells in the South China Sea.