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Using microseismic events to improve the accuracy of sensor orientation for downhole microseismic monitoring
Geophysical Prospecting ( IF 2.6 ) Pub Date : 2021-04-15 , DOI: 10.1111/1365-2478.13099
Yuanhang Huo 1, 2 , Wei Zhang 2, 3 , Jie Zhang 1 , Hui Yang 2, 4
Affiliation  

Event locations are essential for microseismic monitoring endeavours to map hydraulic fractures. For downhole monitoring, the event back-azimuthal angle, which is commonly evaluated as the average of the P-wave polarization angle at each sensor, is necessary to project the 2D location in the vertical plane determined by the traveltime information to the 3D space. The accuracy of the P-wave polarization angle at each sensor depends on the signal-to-noise ratio of the waveforms, as well as relies on the accuracy of the sensor orientation. The conventional approaches of the sensor orientation require an event with known back-azimuth angle, such as surface orientation shots, perforation shots, ball-drop events or teleseismic events. In terms of availability, the signals of the perforation shots or ball-drop events are the most widely used information. But they are usually characterized by a low signal-to-noise ratio. We propose a new method to incorporate high-signal-to-noise ratio microseismic events with unknown back-azimuth angles into the sensor orientation process. It can significantly improve the accuracy of the relative orientation angles among all of the sensors, and also improve the accuracy of the absolute orientation angles by linking the relative orientation angles to the sensors with the high-signal-to-noise ratio waveforms of the perforation shots or ball-drop events. We use both synthetic and field data to test the feasibility and reliability of the new method. The results reveal that the new method can reduce the uncertainty of the orientation angle and improve the accuracy of the microseismic location, compared with the conventional approach when utilizing a perforation shot or ball-drop event alone.

中文翻译:

利用微震事件提高井下微震监测传感器定位精度

事件位置对于绘制水力裂缝的微震监测工作至关重要。对于井下监测,事件后方位角通常被评估为每个传感器的 P 波偏振角的平均值,对于将走时信息确定的垂直平面中的 2D 位置投影到 3D 空间是必要的。每个传感器 P 波偏振角的精度取决于波形的信噪比,以及传感器方向的精度。传感器定向的传统方法需要具有已知后方位角的事件,例如表面定向射击、射孔射击、落球事件或远震事件。就可用性而言,射孔或落球事件的信号是使用最广泛的信息。但它们通常具有低信噪比的特点。我们提出了一种新方法,将具有未知后方位角的高信噪比微地震事件纳入传感器定向过程。它可以显着提高所有传感器之间的相对方位角的精度,也可以通过将相对方位角与穿孔的高信噪比波形链接到传感器来提高绝对方位角的精度投篮或落球事件。我们使用合成数据和现场数据来测试新方法的可行性和可靠性。结果表明,新方法可以降低方位角的不确定性,提高微震定位精度,
更新日期:2021-06-14
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