Accuracy limitations of FOG-based continuous measurement-while-drilling surveying instruments for horizontal wells
Accuracy limitations of FOG-based continuous measurement-while-drilling surveying instruments for horizontal wells
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DOI：
10.1109/tim.2002.808025
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发表时间：
2002-12-01
影响因子：
5.6
通讯作者：
Mintchev, MP
中科院分区：
文献类型：
--
作者：
Noureldin, A;Irvine-Halliday, D;Mintchev, MP
石油工业中的水平钻井过程利用定向随钻测量 (MWD) 仪器来实时监控底部钻具组合 (BHA) 的位置和方向。据报道，单个光纤陀螺仪（FOG）可以与三轴加速度计结合，提供水平井的实时随钻测量。然而，这种基于光纤陀螺仪的仪器系统的长期性能和精度限制尚未得到讨论。本文旨在描述一种在钻井近垂直部分时对各种测量误差进行定量长期分析的方法。它还提供了一些技术来提高基于光纤陀螺的井下测量仪器的实验模型的长期测量精度。测量误差通过卡尔曼滤波技术进行优化估计，其长期分析基于研究相应的均方估计误差。为了限制测量误差的长期增长，我们建议通过连续速度更新或在某些预定测量站进行零速度更新来改进基于光纤陀螺的系统提供的速度计算。这些技术显着限制了位置误差的长期增长（在超过 2 小时的实验中小于 100 m）。此外，与 BHA 定向组件相关的误差保持在小于 1 度。所提出的方法显着提高了基于 FOG 的 MWD 测量系统实验模型的测量精度。
Horizontal drilling processes in the oil industry utilize directional measurement-while-drilling (MWD) instruments to provide real-time monitoring of the position and the orientation of the bottom hole assembly (BHA). It has been reported that a single fiber optic gyroscope (FOG) can be incorporated with three-axis accelerometers to provide real-time MWD surveying of horizontal wells. However, the long-term performance and the accuracy limitations of this FOG-based instrumentation system have not been discussed. This article aims at describing a methodology for quantitative long-term analysis of the various surveying errors while drilling the near-vertical sections of the well. It also offers some techniques to enhance the long-term surveying accuracy in an experimental model of the FOG-based downhole-surveying instrument. The surveying errors are optimally estimated by the Kalman filtering techniques, and their long-term analysis is based on studying the corresponding mean square estimation errors. In order to limit the long-term growth of the surveying errors, we suggest improving the velocity computation provided by the FOG-based system either by continuous velocity update or by zero velocity update at some predetermined surveying stations. These techniques have significantly limited the long-term growth of the position errors (less than 100 m over a more than 2-h experiment). Moreover, the errors associated with the BHA orientation components were kept at less than 1degrees. Suggested methodology significantly improved the surveying accuracy in an experimental model of the FOG-based MWD surveying system.