基于多分量测量的固定翼航空电磁数据电导率深度成像研究

发布时间：2018-05-14 19:53

本文选题：多分量测量 + 固定翼航空电磁探测　；参考：《吉林大学》2015年硕士论文

【摘要】：随着经济水平的不断发展，我国对能源的需求与日俱增，进行高效的资源勘探及开发已势在必行。固定翼航空电磁探测是一种基于法拉第电磁感应定律，以固定翼飞机为载体，采用偶极-偶极收发装置的地球物理探测方法，具有探测效率高、成本低等优势，广泛应用于地质勘查、油气探测、水文普查等领域。固定翼航空电磁数据量庞大，反演解释耗时费力，一般采用电导率深度成像技术(CDI，Conductivity-Depth Imaging)快速处理海量航空电磁数据，得到地下电导率分布图，从而确定地下异常分布。本文依托国家自然科学基金项目“固定翼时间域航空电磁探测整体反演方法研究”以及国家重大科研装备研制专项子课题“航空瞬变电磁系统数据处理与反演成像”，结合固定翼航空电磁探测仪器参数设计，研究了固定翼航空电磁探测三分量一维正演计算以及单分量电导率深度成像算法；基于固定翼航空电磁探测的多分量测量，借助姿态角度等辅助信息，提出了多分量联合电导率深度成像算法，主要研究内容如下：基于航空电磁探测理论，研究了阶跃发射电流的多分量off-time电磁响应计算方法，推导了任意发射电流波形下的多分量二次场全波响应；根据毕奥-萨伐尔定律，得到任意发射电流波形条件下接收线圈处的一次场，从而得到全场响应。基于正演算法，结合仪器参数设计的需要，以梯形发射电流与半正弦发射电流为例，对比研究了不同发射电流参数的电磁响应，经分析得出：若采用梯形发射电流，脉冲宽度为4ms，当上升沿宽度在0.2ms波动，下降沿宽度在0.1ms波动时，电磁响应均方相对误差均低于4%；若采用半正弦发射电流，脉冲宽度为4ms，当脉冲宽度在0.4ms波动时，电磁响应均方相对误差低于4%。固定翼航空电磁探测三分量接收线圈悬挂于飞机下方，难以准确获取大地坐标系下的多分量信息，一般采用总场数据进行解释成像。本文基于正演计算，分析了B场与dB dt电磁响应特点，发现B场能量主要集中在低频段，易于良导体探测；在此基础上分别研究了dB dt与B场的单分量与总场电导率深度成像，仿真实例表明，在良导体探测中，B场较dB dt响应具有更好的成像效果。同时飞行高度及发射电流波形对成像结果的影响表明，飞行高度及发射电流的微小偏差也会引起较大的成像误差。目前随着激光惯导等技术的发展，可以准确测量各分量接收线圈姿态，使得精确获取大地坐标系下的多分量电磁响应成为可能。本文基于多分量测量，结合姿态角度等辅助信息，提出了一种基于B场响应的双分量联合电导率深度成像算法，基于固定翼时间域航空电磁正演理论，建立水平分量磁场(即Bx)-垂直分量磁场(即Bz)-电导率-飞行高度数据表，利用磁场双分量联合查表与插值算法，确定视电导率，根据扩散深度公式得到视深度，并计算成像深度，从而得到双分量联合电导率深度成像结果。本文基于一维大地模型正演数据与准二维大地模型正演加噪数据，分别采用磁场双分量联合查表法、总场查表法和单分量查表法对仿真数据进行电导率深度成像，结果表明磁场双分量联合查表法优于单分量与总场查表法，成像精度提高了7%。最后本文研究了双分量联合电导率深度成像对异常体探测能力的影响，在仪器分辨率为0.01nT时，研究了航空电磁的异常体探测能力，，得到同等仪器分辨率下对应大地模型的分辨极限。基于准二维大地模型正演加噪数据，对比研究了Bx分量查表法、Bz分量查表法、总场查表法以及Bx-Bz分量联合查表法对异常体探测能力的影响，结果证明在同等仪器分辨率的条件下，Bx-Bz分量联合查表法对异常体具有更好的探测能力，相当于间接提高了仪器分辨率。
[Abstract]:With the continuous development of the economic level, China's demand for energy is increasing, and it is imperative to carry out efficient resource exploration and development. Fixed wing aero electromagnetic detection is a geophysical exploration method based on Faraday's law of electromagnetic induction, using the fixed wing aircraft as the carrier and using dipole dipole transceiver, and has the detection efficiency. High, low cost advantages, widely used in geological exploration, oil and gas detection, hydrographic census and other fields. The fixed wing aero electromagnetic data is huge, and the inversion interpretation is time-consuming and laborious. In general, the conductivity depth imaging (CDI, Conductivity-Depth Imaging) is used to quickly deal with the mass aero electromagnetic data and obtain the distribution map of the underground conductivity, thus determining the distribution of the underground conductivity. Abnormal distribution of underground.
This paper, based on the National Natural Science Foundation Project "study on the integrated inversion method of aero electromagnetic detection in fixed wing time domain" and the "data processing and inversion imaging of Aeronautical transient electromagnetic system", and the parameter design of the fixed wing aero electromagnetic explorer, have studied the fixed wing aero electromagnetic field. The three component one dimensional forward calculation and the single component conductivity depth imaging algorithm are detected. Based on the multi component measurement of the fixed wing aero electromagnetic detection and the aid of the attitude angle, the multi component joint conductivity depth imaging algorithm is proposed. The main research contents are as follows:
Based on the theory of aero electromagnetic detection, the multi component off-time electromagnetic response calculation method of step emission current is studied, and the multicomponent two field full wave response under arbitrary emission current is derived. According to Biot Savart law, the first field at the receiving coil under the condition of arbitrary emission current is obtained, and the full field response is obtained. Yu Zheng algorithm, combined with the need of instrument parameter design, takes the trapezoid emission current and the semi sinusoidal emission current as an example to compare and study the electromagnetic response of different emission current parameters. The analysis shows that if the trapezoid emission current is used, the pulse width is 4ms, when the rising edge is in the 0.2ms fluctuation and the drop along the width is in the 0.1ms fluctuation, the electromagnetic response is observed. The relative error of the mean square is less than 4%. If the half sinusoidal emission current is used, the pulse width is 4ms, and the relative error of the electromagnetic response is less than 4%. when the pulse width is fluctuating in the 0.4ms.
The three component receiving coil of fixed wing aero electromagnetic detection is suspended under the aircraft. It is difficult to obtain the multi component information in the geodetic coordinate system. Generally, the total field data is used to explain the imaging. Based on the forward calculation, the electromagnetic response characteristics of B field and dB DT are analyzed. It is found that the energy of the B field is mainly concentrated in the low frequency section, and it is easy to detect the good conductor. On this basis, the single component and total field conductivity depth imaging of dB DT and B field are studied. The simulation example shows that in the good conductor detection, the B field has a better imaging effect than the dB DT response. At the same time, the influence of the flight height and the emission current waveform on the imaging results shows that the slight deviation of the flying height and the emission current will also cause the comparison. Large imaging error.
At present, with the development of laser inertial navigation technology, it is possible to accurately measure the attitude of each component receiving coil, making it possible to obtain the multi component electromagnetic response in the geodetic coordinate system accurately. Based on multicomponent measurement and combined with the auxiliary information of attitude angle, a kind of dual component joint conductivity depth imaging based on B field response is proposed. Method, based on the fixed wing time domain aero electromagnetic forward theory, the horizontal component magnetic field (Bx) vertical component magnetic field (Bz) - conductivity flight height data table is set up. The apparent conductivity is determined by the double component joint lookup and interpolation algorithm of the magnetic field, the apparent depth is obtained according to the diffusion depth formula, and the imaging depth is calculated, thus the dual component is obtained. In this paper, based on the positive data of one dimensional earth model and the quasi two-dimensional geodetic model, this paper uses the magnetic double component joint table method, the total field lookup table method and the single component lookup method to carry on the conductivity depth imaging to the simulation data. The result shows that the magnetic field double component joint lookup method is superior to the single component. The total field look-up table method has improved the imaging precision of 7%.
At the end of this paper, the influence of the dual component combined conductivity depth imaging on the detection ability of abnormal body is studied. When the resolution of the instrument is 0.01nT, the detection ability of the abnormal body of aero electromagnetic is studied and the resolution limit of the corresponding earth model is obtained under the same resolution of the same instrument. Based on the quasi two-dimensional geodetic model, the Bx fraction is compared and studied. The measurement table method, the Bz component look-up table method, the total field lookup table method and the Bx-Bz component joint table method influence the abnormal body detection ability. The results show that under the same resolution conditions, the Bx-Bz component joint look-up table method has better detection ability for the abnormal body, which is equivalent to the indirect lifting of the instrument resolution.

【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.326

【参考文献】