海水绕流作用下表层套管偏移量预测方法研究

Prediction of Conductor Deflection Caused by Sea Water Flow

自升式钻井平台探井作业表层套管下入过程中,套管在海水绕流作用下会发生挠曲,因此需要移动悬臂梁和井架来使套管重入井眼。为克服悬臂梁和井架移动作业的盲目性,研究建立了表层套管偏移量预测模型。算例分析表明,套管偏移量会随海水流速、套管入水深度、顶驱到海面距离的增大而增大,且海水流速的影响最大;忽略套管重力作用将导致套管底部偏移量预测值显著偏高。现场应用结果表明,考虑了重力作用的预测模型,其预测精度能满足工程应用需要,可以有效指导悬臂梁和井架移动作业,提高作业效率。

During the running of surface casing in the exploration operation of jack-up drilling platform,the casing will bend under the action of sea current.In order to make the conductor run into the original wellbore,the cantilever beam and the derrick should be moved.To guide the movement of the cantilever beam and derrick,a quantitative prediction model of conductor deflection is established.Case study shows that conductor deflection increases with the increase of seawater velocity,depth of sea water and distance from top drive to sea surface.The influence of seawater velocity is the largest.Ignoring the casing gravity will lead to significantly higher predicted value of casing bottom offset.The practical application shows that the prediction accuracy of the model can meet the needs of engineering application;the model can effectively guide the movement of the cantilever beam and derrick,and improve the operation efficiency.