Orientation load prediction method based on randomness/stochasticity of multi-source parameters in coiled tubing drilling
Orientation load prediction method based on randomness/stochasticity of multi-source parameters in coiled tubing drilling
复制标题
基于多源参数随机性/随机性的连续油管钻井定向载荷预测方法
DOI：
10.1016/j.petrol.2020.107017
复制
发表时间：
2020
影响因子：
--
通讯作者：
Chen Weiqing
中科院分区：
文献类型：
--
作者：
Li Meng;Hu Shuli;Su Kanhua;Wan Lifu;Guo Xiaole;He Huiqun;Chen Weiqing
井眼轨迹控制一直是定向钻井的关键。井下参数测量和钻具组合的配置与调整对实现有效的井眼轨迹控制起着至关重要的耦合作用。然而，这两个阶段都普遍存在误差。与以往的定值预测模型相比，基于不确定性分析的预测方法将使预测结果更加合理，对钻具组合性能的控制更有意义。针对连续油管钻井过程中井下多源参数的随机性，提出了一种在一定置信度下的定向载荷不确定性预测方法。在梁柱理论的基础上，引入概率统计理论，统计出主要参数的分布形式。推导了连续油管钻井停泵和开泵时定向载荷预测模型的概率密度函数和累积概率函数。对数正态分布与定向载荷的概率函数具有较好的相关性，并对定向载荷的置信区间进行了分析。在此基础上，进行了相关的验证实验，并对连续油管钻井中的不确定定向载荷进行了预测。根据现场试验结果得出了几点结论。钻压、钻柱与井壁或套管界面摩擦系数、工具工作面角度的随机性是影响连续油管钻井定向载荷不确定性的主要因素。用不确定度方法预测的方向载荷不是单一曲线或单一值，而是具有一定置信水平的区间。区间窗的宽度取决于参数信息的准确度和精度。置信度越高，定向载荷的预测区间越宽，不确定性范围越大。与不确定度法的预测结果相比，传统的单值计算法的预测结果存在误差。该误差随钻压和地层的变化而变化，可以是正的，也可以是负的。同时，恢复更准确的主要原始数据，如钻压、地层性质等，将降低预测的不确定性。这种定向载荷预测方法有助于提高连续油管钻井定向钻井的效率。
Well trajectory control is always the key point of directional drilling. Downhole parameters measurements and BHA (bottom hole assembly) configuration and adjustment have the vital and coupling effect on realizing effective and efficient trajectory control. However, error exists universally in both of these phases. Compared with previous fixed value prediction models on controlling parameters prediction, uncertainty analysis based method will make the prediction results more reasonable and meaningful to control the BHA performance. With the consideration of the randomness of downhole multi-source parameters in coiled tubing drilling, an uncertainty prediction method for orientation load at a certain confidence level is proposed. Based on the beam-column theory, the probability and statistics theory is introduced and the distribution forms of main parameters are counted statistically. The probability density function and cumulative probability function of the orientation load prediction model when pump off and pump on in coiled tubing drilling are derived. The lognormal distribution has better correlation with the probability function of the orientation load, and the analysis on the confidence interval of the orientation load is described. Then, several relevant validation experiments are carried out, and the prediction of uncertain orientation load in coiled tubing drilling is also made. Several conclusions are made regarding to the field trial results. The randomness of weight on bit, friction coefficient of the interfacial between drill string and borehole wall or drill string and casing and tool face angle are the principal factors affecting the uncertainty of orientation load in coiled tubing drilling. The orientation load predicted with the uncertainty method is not a single curve or a single value, but an interval with a certain confidence level. The width of interval window is determined by the accuracy and precision of parameters information. The higher the confidence level is, the wider the predicted interval of orientation load and the larger the uncertainty range become. Compared with the predicted results of the uncertainty method, an error exists in the result of traditional single-value calculation method. The error varies with the change of weight on bit and formations and can be positive or negative. Meanwhile, retrieving more accurate principal original dada, e.g. WOB, formation properties, will make the uncertainty of the prediction lower. This orientation load prediction method is helpful to improve the efficiency of directional drilling in coiled tubing drilling.