WO2017070833A1 - 电磁检测仪器的偏置误差校正方法 - Google Patents

电磁检测仪器的偏置误差校正方法 Download PDF

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WO2017070833A1
WO2017070833A1 PCT/CN2015/092923 CN2015092923W WO2017070833A1 WO 2017070833 A1 WO2017070833 A1 WO 2017070833A1 CN 2015092923 W CN2015092923 W CN 2015092923W WO 2017070833 A1 WO2017070833 A1 WO 2017070833A1
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field strength
coil
strength measurement
electromagnetic
vcp
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PCT/CN2015/092923
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French (fr)
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李光
渠晓东
陈洁
黄玲
方广有
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中国科学院电子学研究所
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/12—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with electromagnetic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V13/00—Manufacturing, calibrating, cleaning, or repairing instruments or devices covered by groups G01V1/00 – G01V11/00

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  • the present invention relates to geophysical electromagnetic surveying, and more particularly to an offset error correcting method for an electromagnetic detecting instrument.
  • frequency domain electromagnetic method is widely used in geological survey, mineral exploration, UXO detection and archaeology.
  • the frequency domain electromagnetic method based on magnetic dipoles as transmitting and receiving is also called electromagnetic Slingram method.
  • the basic principle of the Slingram method is to generate a magnetic field signal (ie, a primary field) in the earth through the transmitting coil, and generate a primary field signal to generate an induced eddy current with the earth or a conductive abnormal body, thereby generating a secondary magnetic field signal (ie, The secondary field) receives the corresponding secondary field signal through the receiving coil to achieve the purpose of detecting the earth conductivity distribution or the underground abnormal body.
  • the method does not need to be in contact with the earth, and the Slingram detection instrument can be composed of different coil structures according to different arrangements of the transmitting and receiving coils, including horizontal coplanar (HCP), vertical coplanar (VCP), Vertical Coaxial (VCA) and Orthogonal (PERP) coil architectures are shown in Figure 1.
  • HCP horizontal coplanar
  • VCP vertical coplanar
  • VCA Vertical Coaxial
  • VPA Vertical Coaxial
  • PROP Orthogonal
  • the primary field received by the receiving coil can be theoretically calculated, thereby eliminating the ideal primary field received by the receiving coil.
  • the value is zero for the output of the receiving coil.
  • the output of the receiving coil is not zero, and a corresponding offset error is generated.
  • the existence of the offset error will result in the inability to accurately invert the earth conductivity information from the measured data, so the offset error of the detection instrument needs to be measured and corrected.
  • the offset error correction method of the conventional electromagnetic Slingram method detection instrument mainly includes the following methods.
  • a simple method for correcting the offset error is to place the instrument in the air to minimize the influence of unknown earth and abnormal bodies in the external environment. It can be considered that the non-zero signal received by the receiving coil is the instrument.
  • Offset error, and the RESOLVE system is measured by the helicopter to the height of the offset error (see Cain M J, Resolve survey for US geological survey east poplar oil fields, Montana.FUGRO AIRBORNE SURVEYS Report #04034, 2004); Japan Mitsuhata et al.
  • the second method consists in first measuring the earth conductivity distribution at the position of the measuring point by means of a standard conductivity method instrument, and then using the measured earth conductivity distribution model to correct the offset error of the GEM-2 instrument (Deszcz- Pan M, Fitterman D V, Labson V F. Reduction of inversion errors in helicopter EM data using auxiliary information [J]. Exploration Geophysics, 1998, 29(1/2): 142-146.). For example, Minsley et al. used a DC conductivity method to invert the earth 2D model at the measurement location and used this model to correct the bias error of the slingram instrument (Minsley B J, Smith B D, Hammack R, et al. Calibration and Filtering strategies for frequency domain electromagnetic data [J].
  • This type of method uses other types of conductivity method instruments.
  • the working mechanism is different from that of the Slingram-based instrument.
  • the spatial distribution of the measured conductivity in the earth is also different, which affects the correction of the bias error of the Slingram method. Precision.
  • this method cannot be used for correction.
  • the third method is to measure at different heights at the same measurement point. Since the distribution of the underground conductivity at the same location is the same, it is possible to use the measured values of different heights to jointly invert the underground conductivity information and the offset error of the instrument (Sasaki Y, Son J S, Kim C, et al. Resistivity and Offset error estimations for the small-loop electromagnetic method[J].Geophysics,2008,73(3):F91-F95.;Minsley B J,Kass M A,Hodges G,et al.Multielevation calibration of frequency-domain electromagnetic data [J]. Geophysics, 2014, 79 (5): E201-E216.). This kind of method has great influence on the parameter selection of the earth model when inversion. If the model parameters are not selected correctly, the offset error value of the inversion will be inaccurate.
  • a method for correcting an offset error of an electromagnetic Slingram method detecting instrument comprising the steps of:
  • the first field strength measurement Second field strength measurement And the gradient, calculating an offset error value offset of the electromagnetic detecting instrument, and correcting an offset error of the electromagnetic Slingram method detecting instrument by using the calculated offset error value offset.
  • the electromagnetic Slingram method detecting instrument comprises at least one pair of transceiver coils.
  • the field strength measurement is a secondary field measurement.
  • the at least one pair of transceiver coils are placed along the x-axis and point in the y-axis direction; in the HCP coil architecture, the at least one pair of transceiver coils are disposed along the x-axis and point to z Axis direction.
  • the offset error value offset of the electromagnetic detecting instrument is calculated according to the following equation:
  • I the gradient of the secondary field of the VCP coil architecture for the transmission and reception distance
  • ⁇ 0 is the original transmission and reception distance of the pair of transceiver coils
  • ⁇ 1 is the transmission and reception distance after the pair of transceiver coils are rotated.
  • the angle of rotation is in the range of -26° to +26°.
  • ⁇ z is the displacement of the transmitting and receiving coils along the z-axis before and after the rotation of the coil.
  • the instrument can be realized. Correction of the offset error.
  • it is not necessary to place the electromagnetic detecting instrument in the high air, but the relationship between the secondary field and the secondary field measured by the different placement modes of the instrument itself is adopted. There is also no need for additional conductivity method instruments or determining the parameters of the earth model for inversion correction.
  • Figure 1 shows four coil architectures of a conventional electromagnetic Slingram method instrument.
  • FIG. 2 is a flow chart showing a method of correcting an offset error of an electromagnetic detecting apparatus according to an embodiment of the present invention.
  • Figure 3 shows a schematic diagram of a layered earth measurement by an electromagnetic detection instrument under the VCP coil architecture.
  • Figure 4 shows a schematic diagram of the layered earthwork measured by an electromagnetic detection instrument under the HCP coil architecture.
  • Figure 5 shows a schematic diagram of the electromagnetic detection instrument under the VCP coil architecture rotating about the y-axis at a central point.
  • Embodiments of the present invention provide a bias error correction method for a gradient-based electromagnetic Slingram method detection instrument.
  • the idea of the present application is to first derive the secondary field under the HCP coil architecture based on the layered earth model. Secondary field under VCP coil architecture Gradient of secondary field pair transmission and reception distance under VCP coil architecture And the relationship equation between them Under the condition that the offset error of the same instrument is constant within the time of instrument offset error correction, the Slingram method of VCP coil architecture is used to measure the secondary field under the VCP coil structure.
  • an offset error correction method of an electromagnetic Slingram method detecting instrument may include:
  • step S103 the VCP coil is rotated at a center point thereof by a corresponding angle around the y-axis and the third field strength measurement after the rotation is obtained.
  • step S105 according to the second field strength measurement value And the third field strength measurement Calculating the gradient of the secondary field to the transmission and reception distance under the VCP coil architecture;
  • step S107 according to the first field strength measurement value Second field strength measurement And the gradient, calculating the offset error value offset of the electromagnetic Slingram method detecting instrument, and correcting the offset error of the electromagnetic detecting instrument by using the calculated offset error value offset.
  • Figure 3 shows the Slingram test instrument under the VCP coil architecture.
  • the transceiver coils are placed along the x-axis and are all pointing in the y-axis direction.
  • the coordinates of the transmitting coil are (0, 0, z t ), and the coordinates of the receiving coil are (x r , y r , z r ). If the VCP coil structure is rotated 90 degrees along the x-axis, the Slingram test instrument under the HCP coil structure can be obtained, as shown in Fig. 4.
  • the secondary field received by the receiving coil under the VCP and HCP coil architecture can be expressed by the following formula:
  • the secondary field component value received by the y-axis The value of the secondary field component received by the z-axis for the z-axis.
  • J 0 ( ⁇ ), J 1 ( ⁇ ) are the first-order 0-order Bessel function and the first-order first-order Bessel function;
  • m is the emission magnetic moment, and N is an integer greater than or equal to 1.
  • r TE is the reflection coefficient and can be determined by:
  • the Slingram detection instrument of the VCP coil structure is rotated at a small angle around the y-axis at its center point, as shown in FIG. 5, so that the transmitting and receiving coils are moved up and down by ⁇ z, satisfying the coordinates of the z-axis of the transmitting and receiving coils before and after the rotation, that is, z
  • the measured values at the same measurement point have the same reflection coefficient, which is independent of the layer number and conductivity distribution of the layered earth model, and the specific parameters of the layered earth model may not be considered.
  • the method according to an embodiment of the invention is simple and easy. Those skilled in the art will appreciate that multiple measurements can be made to more accurately determine the offset error value of the instrument system in an averaging manner. Moreover, due to the relationship between the VCP coil architecture and the HCP coil architecture, those skilled in the art can readily apply the embodiments of the present invention to the correction of the HCP coil architecture.
  • the electromagnetic Slingram method detecting apparatus in the embodiment includes only one transceiver coil pair.
  • the electromagnetic detecting instrument may also be a VCP coil structure having a plurality of transmitting coils and a plurality of receiving coils; the correction may be performed by separately performing correction.
  • the embodiment of the present invention can be applied to a transmitting and receiving coil of any shape, as long as it can be equivalent to a magnetic dipole;
  • the rotation angle can be arbitrarily selected; generally, ⁇ z ⁇ /10 is taken, and the rotation angle is changed between -26° and +26°.
  • the gradient of the secondary field to the transmission and reception distance under the VCP coil structure can be obtained by the secondary field measured by any two rotations around the y-axis, and is not limited to the secondary field measured by the horizontal state.

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Abstract

一种电磁检测仪器的偏置误差校正方法，包括步骤：获得针对HCP线圈架构的第一场强测量值和针对VCP线圈架构的第二场强测量值（S101）；将VCP线圈架构在其中心点处围绕y轴旋转一个角度并获得旋转后的第三场强测量值（S103）；根据第二场强测量值和第三场强测量值计算二次场对于收发距的梯度（S105）；根据第一场强测量值、第二场强测量值、和梯度，计算电磁Slingram法检测仪器的偏置误差值（S107），利用了仪器本身不同的摆放方式所测得的二次场及二次场对于收发距的梯度之间的关系，可实现对电磁Slingram法检测仪器偏置误差的校正，而不需要额外的电导率法仪器或确定大地模型的参数进行反演校正。

Description

电磁检测仪器的偏置误差校正方法 技术领域
本发明涉及地球物理电磁勘探，更具体地，涉及一种电磁检测仪器的偏置误差校正方法。
背景技术
频率域电磁法作为地球物理电磁法勘探的一种，广泛应用于地质普查、矿物勘探、UXO探测以及考古等领域。其中，基于磁偶极子作为发射与接收的频率域电磁法又称为电磁Slingram方法。Slingram方法的工作的基本原理是：通过发射线圈在大地中产生一次磁场信号(即一次场)，产生的一次场信号与大地或可导异常体作用产生感应涡流，进而产生二次磁场信号(即二次场)，通过接收线圈接收相应的二次场信号，达到探测大地电导率分布或地下异常体的目的。该方法不需要与大地接触，且根据收发线圈不同的排布可组成不同线圈架构的Slingram法检测仪器，包括水平共面(Horizontal Coplanar，即HCP)、垂直共面(Vertical Coplanar，即VCP)、垂直共轴(Vertical Coaxial，即VCA)以及正交(Perpendicular，即PERP)线圈架构，如图1所示。
基于电磁Slingram法检测仪器的工作原理，在没有外部二次场输入且收发线圈位置固定的情况下，由接收线圈接收到的一次场可以理论算出，进而可以消除掉接收线圈接收到的理想一次场值，实现接收线圈的输出为零。但是由于收发线圈的位置偏差(一次场影响)、接收线圈的特性以及后续调理电路等因素的影响使得接收线圈的输出不为零，会产生相应的偏置误差。而偏置误差的存在将导致由测得的数据无法准确地反演出大地电导率信息，因此需要对检测仪器的偏置误差进行测量并校正。传统电磁Slingram法检测仪器的偏置误差校正方法主要包括以下方法。
一种较简单的偏置误差校正方法在于：将仪器放置于高空中，使其受外部环境中未知大地及异常体的影响达到最小，可以认为此时接收线圈接收到的非零信号是仪器的偏置误差，而RESOLVE系统就是被直升机拉至高空测得其偏置误差(参见Cain M J，Resolve survey for US geological survey east poplar oil fields，Montana.FUGRO AIRBORNE SURVEYS Report#04034，2004)；日本的Mitsuhata等人将GEM-2竖直放 置并抬至4m高的位置，此时测得的虚部及实部响应分别接近于将GEM-2水平放置并分别抬至7m的虚部，10m高的实部响应，以实现对未知大地及异常体响应的抑制，且认为此时测量的值为系统的偏置误差值(Mitsuhata Y，Imasato T.On-site bias noise correction in multi-frequency slingram-type electromagnetic induction measurements[J].Journal of Environmental&Engineering Geophysics，2009，14(4)：179-188.)。该类方法对于航空的Slingram法检测仪器较容易实现，而对于地面的Slingram法检测仪器则不切实际，且存在若仪器被拉至的高度不够高时，测得的偏置误差值误差较大的问题。
第二种方法在于：先通过标准的电导率法仪器测量出测点位置处的大地电导率分布，再利用测得的大地电导率分布模型实现对GEM-2仪器偏置误差的校正(Deszcz-Pan M，Fitterman D V，Labson V F.Reduction of inversion errors in helicopter EM data using auxiliary information[J].Exploration Geophysics，1998，29(1/2)：142-146.)。如Minsley等人利用直流电导率法仪器反演出测量位置处的大地2D模型，并利用该模型校正了slingram法仪器的偏置误差(Minsley B J，Smith B D，Hammack R，et al.Calibration and filtering strategies for frequency domain electromagnetic data[J].Journal of Applied Geophysics，2012，80：56-66.)。该类方法采用其它类型的电导率法仪器，其工作机理与基于Slingram法的仪器不同，相应测得的电导率在大地中的空间分布也不相同，进而影响Slingram法检测仪器偏置误差的校正精度。此外，若野外实验中仅有Slingram法检测仪器的情况下，则无法采用该类方法进行校正。
第三种方法则是通过对同一测量点处，采用不同的高度进行测量。由于同一位置处地下电导率的分布是一样的，可以利用不同高度的测量值联合反演出地下电导率信息，以及仪器的偏置误差(Sasaki Y，Son J S，Kim C，et al.Resistivity and offset error estimations for the small-loop electromagnetic method[J].Geophysics，2008，73(3)：F91-F95.；Minsley B J，Kass M A，Hodges G，et al.Multielevation calibration of frequency-domain electromagnetic data[J].Geophysics，2014，79(5)：E201-E216.)。该类方法受反演时大地模型的参数选取影响大，若模型参数选取不正确，反演的偏置误差值也会不准确。
因此，需要一种电磁Slingram法检测仪器的偏置误差校正方法来克服传统技术中的上述问题。
发明内容
根据本发明的一个方面，提出了一种电磁Slingram法检测仪器的偏置误差校正方法，包括步骤：
获得针对HCP线圈架构的第一场强测量值
Figure PCTCN2015092923-appb-000001
和针对VCP线圈架构的第二场强测量值
Figure PCTCN2015092923-appb-000002
将所述VCP线圈架构在其中心点处围绕y轴旋转一个旋转角度并获得旋转后的第三场强测量值
Figure PCTCN2015092923-appb-000003
根据第二场强测量值
Figure PCTCN2015092923-appb-000004
和第三场强测量值
Figure PCTCN2015092923-appb-000005
计算二次场对于收发距的梯度；
根据第一场强测量值
Figure PCTCN2015092923-appb-000006
第二场强测量值
Figure PCTCN2015092923-appb-000007
和所述梯度，计算所述电磁检测仪器的偏置误差值offset，并利用计算的偏置误差值offset对所述电磁Slingram法检测仪器的偏置误差进行校正。
优选地，所述电磁Slingram法检测仪器包括至少一对收发线圈。
优选地，所述场强测量值是二次场测量值。
优选地，在所述VCP线圈架构中，所述至少一对收发线圈沿x轴放置且指向y轴方向；在所述HCP线圈架构中，所述至少一对收发线圈沿x轴设置且指向z轴方向。
优选地，根据以下等式计算所述电磁检测仪器的偏置误差值offset：
Figure PCTCN2015092923-appb-000008
其中，
Figure PCTCN2015092923-appb-000009
是所述VCP线圈架构下的二次场对于收发距的梯度，ρ0是所述收发线圈对的原始收发距，ρ1是所述收发线圈对旋转之后的收发距。
优选地，所述旋转角度在-26°～+26°的范围内。
优选地，
Figure PCTCN2015092923-appb-000010
其中Δz是线圈旋转前后收发线圈沿z轴的位移。
根据本发明实施例的偏置误差校正方法，由于测量的二次场中包含偏置误差，而VCP线圈架构下二次场对于收发距的梯度中不包含偏置误差，可以实现对仪器的 偏置误差的校正。根据本发明实施例的方法，不需要将电磁检测仪器放置于高空中，而是利用了仪器本身不同的摆放方式所测得的二次场及二次场对于收发距的梯度之间的关系，也不需要额外的电导率法仪器或确定大地模型的参数进行反演校正。
附图说明
通过以下参照附图对本发明实施例的描述，本公开的上述以及其他目的、特征和优点将更为清楚，在附图中：
图1示出了传统电磁Slingram法检测仪器的四种线圈架构。
图2示出了本发明实施例的电磁检测仪器的偏置误差校正方法流程图。
图3示出了VCP线圈架构下的电磁检测仪器测量层状大地示意图。
图4示出了HCP线圈架构下的电磁检测仪器测量层状大地示意图。
图5示出了VCP线圈架构下的电磁检测仪器在中心点处绕y轴旋转示意图。
具体实施方式
现在对本发明的实施例提供详细参考，其范例在附图中说明，图中相同的数字代表相同的元件。将参考附图来描述本发明实施例。
本发明实施例提供了一种基于梯度的电磁Slingram法检测仪器的偏置误差校正方法。本申请的思想在于，首先基于层状大地模型，正演推导出HCP线圈架构下的二次场
Figure PCTCN2015092923-appb-000011
VCP线圈架构下的二次场
Figure PCTCN2015092923-appb-000012
VCP线圈架构下二次场对收发距的梯度
Figure PCTCN2015092923-appb-000013
以及它们之间的关系等式
Figure PCTCN2015092923-appb-000014
在仪器偏置误差校正的时间内同一台仪器偏置误差恒定不变的情况下，利用VCP线圈架构的Slingram法仪器分别测量VCP线圈架构下的二次场
Figure PCTCN2015092923-appb-000015
绕所定义坐标系的x轴旋转90度测得HCP线圈架构下的二次场
Figure PCTCN2015092923-appb-000016
在其中心点处绕所定义坐标系的y轴旋转较小的角度下测得旋转后的VCP线圈架构下的二次场
Figure PCTCN2015092923-appb-000017
可以求出VCP线圈架构下的二次场对于收发距的梯度
Figure PCTCN2015092923-appb-000018
由于测得的二次场中包含偏置误差，而VCP线圈架构下二次场对于收发距的梯度中不包含偏置误差，可以实现对仪器偏置误差的校正。
图2示出了本发明实施例的电磁Slingram法检测仪器的偏置误差校正方法的流程图。如图2所示，一种电磁Slingram法检测仪器的偏置误差校正方法可以包括：
在步骤S101，获得针对HCP线圈架构的第一场强测量值
Figure PCTCN2015092923-appb-000019
和针对VCP线圈架构的第二场强测量值
Figure PCTCN2015092923-appb-000020
在步骤S103，将所述VCP线圈在其中心点处围绕y轴旋转相应的角度并获得旋转后的第三场强测量值
Figure PCTCN2015092923-appb-000021
在步骤S105，根据第二场强测量值
Figure PCTCN2015092923-appb-000022
和第三场强测量值
Figure PCTCN2015092923-appb-000023
计算VCP线圈架构下二次场对于收发距的梯度；
在步骤S107，根据第一场强测量值
Figure PCTCN2015092923-appb-000024
第二场强测量值
Figure PCTCN2015092923-appb-000025
和所述梯度，计算所述电磁Slingram法检测仪器的偏置误差值offset，并利用计算的偏置误差值offset对所述电磁检测仪器的偏置误差进行校正。
下文将结合图2-5来详细描述根据本发明实施例的电磁Slingram法检测仪器的偏置误差校正方法。
图3所示为VCP线圈架构下的Slingram法检测仪器，其收发线圈沿着x轴向摆放，且均指向y轴方向。其中发射线圈的坐标为(0，0，zt)，接收线圈的坐标为(xr，yr，zr)。若将VCP线圈架构沿着x轴向旋转90度即可得到HCP线圈架构下的Slingram法检测仪器，如图4所示。
如图3和图4所示，在共计N层的层状大地模型下，VCP及HCP线圈架构下接收线圈接收到的二次场可以由以下公式表示：
Figure PCTCN2015092923-appb-000026
其中
Figure PCTCN2015092923-appb-000027
为y轴发射，y轴接收的二次场分量值，
Figure PCTCN2015092923-appb-000028
为z轴发射，z轴接收的二次场分量值。
Figure PCTCN2015092923-appb-000029
为收发距，即，发射线圈与接收线圈之间的水平距离；J0(λρ)，J1(λρ)分别为第一类0阶贝塞尔函数和第一类1阶贝塞尔函数；m为发射磁矩，N是大于等于1的整数。其中rTE是反射系数，可以由下式确定：
Figure PCTCN2015092923-appb-000030
Figure PCTCN2015092923-appb-000031
Figure PCTCN2015092923-appb-000032
Figure PCTCN2015092923-appb-000033
Figure PCTCN2015092923-appb-000034
其中kn为层状大地第n层的波数，满足
Figure PCTCN2015092923-appb-000035
其中μn，σn分别为层状大地的磁导率及电导率，通常认为大地的磁导率等于自由空间的磁导率，即μn＝μ0；ω为发射线圈发射的角频率；hn为层状大地第n层的厚度；满足层状大地最底层即第N层
Figure PCTCN2015092923-appb-000036
已知第一类0阶贝塞尔函数与第一类1阶贝塞尔函数J0(λρ)，J1(λρ)满足下式：
Figure PCTCN2015092923-appb-000037
因此，在yr＝0的情况下，可得到HCP线圈架构下的二次场、VCP线圈架构下的二次场，以及VCP线圈架构下二次场对于收发距的梯度之间的关系式：
Figure PCTCN2015092923-appb-000038
将VCP线圈架构的Slingram法检测仪器在其中心点处绕y轴旋转较小的角度，如图5所示，使得收发线圈上下均移动Δz，满足旋转前后收发线圈z轴向的坐标和即zt+zr的值不变，Δz＜＜ρ且仪器的线圈轴向未发生变化，而只有收发距(收发线圈之间的水平距离)发生了变化。认为未发生旋转时的状态为状态0，而发生旋转后的状态为状态1。即旋转之前的收发距为ρ0＝ρ，而旋转之后的收发距为
Figure PCTCN2015092923-appb-000039
可以根据旋转前后
Figure PCTCN2015092923-appb-000040
的差分代替上述式4中的梯度。
Figure PCTCN2015092923-appb-000041
在层状大地模型下，由于偏置误差的存在，且满足偏置误差在校正的时间内是恒定不变的，则有下式成立：
Figure PCTCN2015092923-appb-000042
Figure PCTCN2015092923-appb-000043
Figure PCTCN2015092923-appb-000044
其中
Figure PCTCN2015092923-appb-000045
为不考虑偏置误差的理论测量值；
Figure PCTCN2015092923-appb-000046
和
Figure PCTCN2015092923-appb-000047
为相应的实际测量值，其中均包含有相同的偏置误差。将式5、6带入式4中，则可以得到电磁检测仪器的偏置误差值：
Figure PCTCN2015092923-appb-000048
由上式可知，可以根据线圈旋转之前的测量值
Figure PCTCN2015092923-appb-000049
测量值
Figure PCTCN2015092923-appb-000050
原始收发距以及旋转前后二次场对于收发距的梯度来得到电磁检测仪器的偏置误差值。
由于
Figure PCTCN2015092923-appb-000051
均为在同一测量点处的测量值，具有相同的反射系数，与层状大地模型的层数及电导率分布无关，可以不用考虑层状大地模型的具体参数。根据本发明实施例的方法简单易行。本领域技术人员可以理解，可以进行多次测量，以求平均的方式更加精确地求取仪器系统的偏置误差值。此外，由于VCP线圈架构与HCP线圈架构之间的关系，本领域技术人员可以容易地将本发明实施例用于HCP线圈架构的校正。
此外，上述对各元件和方法的定义并不仅限于实施例中提到的各种具体结构、形状或方式，本领域普通技术人员可对其进行更改或替换而不超出本发明的保护范围，例如：
(1)实施例中电磁Slingram法检测仪器仅包括一个收发线圈对。电磁检测仪器也可以是具有多个发射线圈、多个接收线圈的VCP线圈架构；可通过分别进行校正的方式实施校正。
(2)本发明实施例可用于任意形状的收发线圈，只要能够等效为磁偶极子即可；
(3)适用于满足旋转角度较小，Δz＜＜ρ的条件下，旋转角度可以任意选取；一般取Δz≤ρ/10，此时旋转角度在-26°～+26°之间变化。
(4)VCP线圈架构下二次场对收发距的梯度可由任意两次绕y轴旋转所测得的二次场求出，而不局限于校正时必须包含水平状态测得的二次场。
尽管已经参考本发明的典型实施例，具体示出和描述了本发明，但本领域普通技术人员应当理解，在不脱离所附权利要求所限定的本发明的精神和范围的情况下，可以对这些实施例进行形式和细节上的多种改变。

Claims (7)

  1. 一种电磁Slingram法检测仪器的偏置误差校正方法，包括步骤：
    获得针对HCP线圈架构的第一场强测量值
    Figure PCTCN2015092923-appb-100001
    和针对VCP线圈架构的第二场强测量值
    Figure PCTCN2015092923-appb-100002
    将所述VCP线圈架构在其中心点处围绕y轴旋转一个旋转角度并获得旋转后的第三场强测量值
    Figure PCTCN2015092923-appb-100003
    根据第二场强测量值
    Figure PCTCN2015092923-appb-100004
    和第三场强测量值
    Figure PCTCN2015092923-appb-100005
    计算VCP线圈架构下二次场对于收发距的梯度；
    根据第一场强测量值
    Figure PCTCN2015092923-appb-100006
    第二场强测量值
    Figure PCTCN2015092923-appb-100007
    和所述梯度，计算所述电磁Slingram法检测仪器的偏置误差值offset，并利用计算的偏置误差值offset对所述电磁检测仪器的偏置误差进行校正。
  2. 根据权利要求1所述的方法，其中，所述电磁Slingram法检测仪器包括至少一个收发线圈对。
  3. 根据权利要求2所述的方法，其中，所述场强测量值是二次场测量值。
  4. 根据权利要求2所述的方法，其中，在所述VCP线圈架构中，所述至少一对收发线圈沿x轴放置且指向y轴方向；在所述HCP线圈架构中，所述至少一对收发线圈沿x轴放置且指向z轴方向。
  5. 根据权利要求2所述的方法，其中，根据以下等式计算所述电磁检测仪器的偏置误差值offset：
    Figure PCTCN2015092923-appb-100008
    其中，
    Figure PCTCN2015092923-appb-100009
    是所述VCP线圈架构下二次场对于收发距的梯度，ρ0是所述收发线圈对的原始收发距，ρ1是所述收发线圈对旋转之后的收发距。
  6. 根据权利要求2所述的方法，其中，所述旋转角度在-26°～+26°之间。
  7. 根据权利要求5所述的方法，其中，
    Figure PCTCN2015092923-appb-100010
    其中Δz是线圈旋转前后收发线圈沿z轴的位移。
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140012505A1 (en) * 2011-03-31 2014-01-09 Laurentian University Of Sudbury Multi-component electromagnetic prospecting apparatus and method of use thereof
CN104237956A (zh) * 2014-03-06 2014-12-24 长安大学 电性源瞬变电磁地空探测方法
US20150048834A1 (en) * 2013-08-13 2015-02-19 Groundwater Imaging Pty Ltd Towable transient electromagnetic survey device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140012505A1 (en) * 2011-03-31 2014-01-09 Laurentian University Of Sudbury Multi-component electromagnetic prospecting apparatus and method of use thereof
US20150048834A1 (en) * 2013-08-13 2015-02-19 Groundwater Imaging Pty Ltd Towable transient electromagnetic survey device
CN104237956A (zh) * 2014-03-06 2014-12-24 长安大学 电性源瞬变电磁地空探测方法

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