基于概率理论的连续管钻井调整工具面扭矩预测方法研究

Torque Calculation Method for Adjusting Tool Face during CTD Based on Probability Theory

为研究不确定性因素对连续管钻井(CTD)过程中调整工具面扭矩的影响,构建了基于概率理论的分析方法预测调整工具面扭矩的基本思想。在建立调整工具面扭矩模型的基础上,采用Monte-Carlo法对钻压、地层摩擦因数、井眼曲率等参数的随机性进行了模拟统计试验,得到了各参数及等效接触力的分布形式,并推导出调整工具面扭矩的概率分布函数。通过现场实例分析了参数的随机性对CTD调整工具面扭矩不确定性的影响,并与实测扭矩进行了对比分析。结果表明,不确定性分析方法预测的调整工具面的扭矩不是单一曲线,而是与累积概率有关的区间,区间窗口的大小与参数信息的精确程度有关,置信水平越高,扭矩预测区间的窗口越大,反之,置信水平越低,扭矩预测区间的窗口越小。预测结果与实测扭矩具有较好的一致性,说明采用概率理论预测扭矩更加科学合理。该方法对CTD定向过程中的扭矩预测以及CTD定向工具的设计及应用具有一定的指导意义。

For studying uncertain factors affecting the calculation of torque for tool face adjustment during CTD,the basic idea for the calculation of torque based on probability analysis method is built.Based on the torque model of adjusting the tool face during CTD,Monte-Carlo method is used for the simulation of parameters,such as weight on bit,friction coefficient and borehole curvature.According to the simulation results,the distribution of the parameters and the equivalent contact force are obtained.The probability distribution function of torque is obtained.A field example is presented to demonstrate the effects of random field parameters on the uncertainty of torque.These results are compared with the measured torque.The results show that the torque obtained from the uncertainty method is not a single curve and it is an interval related with cumulative probability.The size of interval windows is related to the accuracy of parameters.The higher the confidence level is,the wider the torque range is,otherwise the lower the confidence level is,the narrower the window for torque range is.The calculation results agree well with the field test value.Therefore,the method based on uncertainty theory is more scientific and reasonable.The probability analysis method can provide reference for the calculation of torque and the design and application of CTD orientation tool.