基于改进tilt梯度的三维磁异常解释技术
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摘要
当工区存在强剩磁或范围较大时,化极处理很难获得满意结果。为此,本文基于tilt梯度,推广得到可以突出x、y方向信息的tilt梯度分量,并根据这两个分量的水平导数,提出了改进tilt梯度水平总梯度的三维磁异常解释技术。该方法可以直接计算三维磁异常,无需化极。理论模型实验表明,相对于其他常用的磁数据处理方法,本文方法可以有效识别不同磁化方向下的长方体边界及球体质心的水平位置,具有更高的分辨率和精度。将该方法应用于中国内蒙塔木素地区航磁数据,解释结果与地质资料及地震推断结果对应较好,为研究区圈定隐伏磁性体提供了依据。
The delineation of magnetic anomaly and the division of structure are the important contents of the magnetic exploration.There is often no correspondence between the magnetic anomaly and the geologic body because of the influence of magnetization direction.At present,most methods for 3 D magnetic interpretation require the magnetic anomaly reduced to the pole beforehand.However,it is difficult to achieve satisfactory results by reduction to the pole when a study area is relatively large or magnetic anomaly contains remanence.In addition,magnetic reduction to the pole may bring errors,which results in the failure of exploration.This paper proposes a 3 D magnetic interpretation technique that can be directly used without reduced to the pole of magnetic anomaly.The proposed method is based on improved tilt angle,which can highlight the information of magnetic sources in the x and y directions.Model tests show that the proposed method can effectively identify the horizontal positions of the boundaries of prisms and sphere's centroid.Furthermore,the proposed method achieves better resolution and better identification of magnetic anomaly compared to other methods.The proposed method is applied to aeromagnetic data from Tamusu of Inner Mongolia,North China,and obtains detailed information of magnetic sources.The results have good correspondence with the geological data and seismic interpretation.In addition,the calculation results of the proposed method provide guides for delineation of hidden magnetic sources in the study area.
The delineation of magnetic anomaly and the division of structure are the important contents of the magnetic exploration.There is often no correspondence between the magnetic anomaly and the geologic body because of the influence of magnetization direction.At present,most methods for 3 D magnetic interpretation require the magnetic anomaly reduced to the pole beforehand.However,it is difficult to achieve satisfactory results by reduction to the pole when a study area is relatively large or magnetic anomaly contains remanence.In addition,magnetic reduction to the pole may bring errors,which results in the failure of exploration.This paper proposes a 3 D magnetic interpretation technique that can be directly used without reduced to the pole of magnetic anomaly.The proposed method is based on improved tilt angle,which can highlight the information of magnetic sources in the x and y directions.Model tests show that the proposed method can effectively identify the horizontal positions of the boundaries of prisms and sphere's centroid.Furthermore,the proposed method achieves better resolution and better identification of magnetic anomaly compared to other methods.The proposed method is applied to aeromagnetic data from Tamusu of Inner Mongolia,North China,and obtains detailed information of magnetic sources.The results have good correspondence with the geological data and seismic interpretation.In addition,the calculation results of the proposed method provide guides for delineation of hidden magnetic sources in the study area.
引文
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[3] 马龙,孟军海,付强,等.独立分量分析在重磁数据处理中的应用[J].石油地球物理勘探,2017,52(6):1344-1353.MA Long,MENG Junhai,FU Qiang,et al.Application of independent component analysis in gravity and magnetic data processing[J].Oil Geophysical Prospecting,2017,52(6):1344-1353.
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[6] Nabighian M N.The analytic signal of two-dimensional magnetic bodies with polygonal cross-section:Its properties and use for automated anomaly interpretation[J].Geophysics,1972,37(3):507-517.
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[14] Li X.Understanding 3D analytic signal amplitude[J].Geophysics,2006,71(2):L13-L16.
[15] Verduzco B,Fairhead J D,Green C M.New insights into magnetic derivatives for structural mapping[J].The Leading Edge,2004,23(2):116-119.
[16] Wijns C,Perez C,Kowalczyk P.Theta map:Edge detection in magnetic data[J].Geophysics,2005,70(4):L39-L43.
[17] 邰振华,张凤旭,刘国兴,等.基于差分求导的伪总梯度余弦值法的位场边界检测[J].石油地球物理勘探,2014,49(4):807-814.TAI Zhenhua,ZHANG Fengxu,LIU Guoxing,et al.Potential field edge detection based on difference derivative with cosine of pseudo total gradient[J].Oil Geophysical Prospecting,2014,49(4):807-814.
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[19] Schmidt P,Clark D,Leslie K,et al.GETMAG:a SQUID magnetic tensor gradiometer for mineral and oil exploration[J].Exploration Geophysics,2004,35(1):297-305.
[20] Schmidt P W,Clark D A.The magnetic gradient tensor:Its properties and uses in source characterization[J].The Leading Edge,2006,25(1):75-78.
[21] Beiki M,Clark D A,Austin J R,et al.Estimating source location using normalized magnetic source strength calculated from magnetic gradient tensor data[J].Geophysics,2012,77(6):J23-J37.
[22] 马国庆,李丽丽,杜晓娟.磁张量数据的边界识别和解释方法[J].石油地球物理勘探,2012,47(5):815-821.MA Guoqing,LI Lili,DU Xiaojuan.Boundary detection and interpretation by magnetic gradient tensor data[J].Oil Geophysical Prospecting,2012,47(5):815-821.
[23] 张恒磊,Marangoni Y R,左仁广,等.改进的各向异性标准化方差探测斜磁化磁异常源边界[J].地球物理学报,2014,57(8):2724-2731.ZHANG Henglei,Marangoni Y R,ZUO Renguang et al.The improved anisotropy normalized variance for detecting non-vertical magnetization anomalies[J].Chinese Journal of Geophysics,2014,57(8):2724-2731.
[24] 周文纳,杜晓娟,李吉焱.重力数据的平面全张量梯度角度边界识别方法[J].石油地球物理勘探,2013,48(6):1009-1015.ZHOU Wenna,DU Xiaojuan,LI Jiyan.Gravity data edge identification using plane full tensor gradient angle[J].Oil Geophysical Prospecting,2013,48(6):1009-1015.
[25] 王万银.位场总水平导数极值位置空间变化规律研究[J].地球物理学报.2010,53(9):2257-2270.WANG Wanyin.Spatial variation law of the extreme value positions of total horizontal derivative for potential field data[J].Chinese Journal of Geophysics,2010,53(9):2257-2270.
[2] Miller H G,Singh V.Potential field tilt:a new concept for location of potential field sources[J].Journal of Applied Geophysics,1994,32(1):213-217.
[3] 马龙,孟军海,付强,等.独立分量分析在重磁数据处理中的应用[J].石油地球物理勘探,2017,52(6):1344-1353.MA Long,MENG Junhai,FU Qiang,et al.Application of independent component analysis in gravity and magnetic data processing[J].Oil Geophysical Prospecting,2017,52(6):1344-1353.
[4] 王彦国,张凤旭,刘财,等.位场垂向梯度最佳自比值的边界检测技术[J].地球物理学报,2013,56(7):2463-2472.WANG Yanguo,ZHANG Fengxu,LIU Cai,et al.Edge detection in potential fields using optimal auto-ratio of vertical gradient[J].Chinese Journal of Geophysics,2013,56(7):2463-2472.
[5] 英高海,姚长利,郑元满,等.基于磁异常的边界特征增强方法对比研究[J].地球物理学报,2016,59(11):4383-4398.YING Gaohai,YAO Changli,ZHENG Yuanman,et al.Comparative study on methods of edge enhancement of magnetic anomalies[J].Chinese Journal of Geophysics,2016,59(11):4383-4398.
[6] Nabighian M N.The analytic signal of two-dimensional magnetic bodies with polygonal cross-section:Its properties and use for automated anomaly interpretation[J].Geophysics,1972,37(3):507-517.
[7] Hsu S K.Depth to magnetic source using the generali-zed analytic signal[J].Geophysics,1998,63(6):1947-1957.
[8] Bastani M,Pedersen L B.Automatic interpretation of magnetic dike parameters using the analytical signal technique[J].Geophysics,2001,66(2):551-561.
[9] Salem A,Ravat D.A combined analytic signal and Euler method (AN-EUL) for automatic interpretation of magnetic data[J].Geophysics,2003,68(6):1952-1961.
[10] Ma G,Du X.An improved analytic signal technique for the depth and structural index from 2D magnetic anomaly data[J].Pure and Applied Geophysics,2012,169(6):2193-2200.
[11] Cooper G R J.Using the analytic signal amplitude to determine the location and depth of thin dikes from magnetic data[J].Geophysics,2015,80(1):J1-J6.
[12] Roeat W R,Verhoef J,Pilkington M.Magnetic interpretation using the 3-D analytic signal[J].Geophy-sics,1992,57(1):116-125.
[13] Hsu S K,Sibuet J C,Shyu C T.High-resolution detection of geologic boundaries from potential-field anomalies:An enhanced analytic signal technique[J].Geophysics,1996,61(2):373-386.
[14] Li X.Understanding 3D analytic signal amplitude[J].Geophysics,2006,71(2):L13-L16.
[15] Verduzco B,Fairhead J D,Green C M.New insights into magnetic derivatives for structural mapping[J].The Leading Edge,2004,23(2):116-119.
[16] Wijns C,Perez C,Kowalczyk P.Theta map:Edge detection in magnetic data[J].Geophysics,2005,70(4):L39-L43.
[17] 邰振华,张凤旭,刘国兴,等.基于差分求导的伪总梯度余弦值法的位场边界检测[J].石油地球物理勘探,2014,49(4):807-814.TAI Zhenhua,ZHANG Fengxu,LIU Guoxing,et al.Potential field edge detection based on difference derivative with cosine of pseudo total gradient[J].Oil Geophysical Prospecting,2014,49(4):807-814.
[18] Pedersen L B,Rasmussen T M.The gradient tensor of potential field anomalies:Some implications on data collection and data processing of maps[J].Geophy-sics,1990,55(12):1558-1566.
[19] Schmidt P,Clark D,Leslie K,et al.GETMAG:a SQUID magnetic tensor gradiometer for mineral and oil exploration[J].Exploration Geophysics,2004,35(1):297-305.
[20] Schmidt P W,Clark D A.The magnetic gradient tensor:Its properties and uses in source characterization[J].The Leading Edge,2006,25(1):75-78.
[21] Beiki M,Clark D A,Austin J R,et al.Estimating source location using normalized magnetic source strength calculated from magnetic gradient tensor data[J].Geophysics,2012,77(6):J23-J37.
[22] 马国庆,李丽丽,杜晓娟.磁张量数据的边界识别和解释方法[J].石油地球物理勘探,2012,47(5):815-821.MA Guoqing,LI Lili,DU Xiaojuan.Boundary detection and interpretation by magnetic gradient tensor data[J].Oil Geophysical Prospecting,2012,47(5):815-821.
[23] 张恒磊,Marangoni Y R,左仁广,等.改进的各向异性标准化方差探测斜磁化磁异常源边界[J].地球物理学报,2014,57(8):2724-2731.ZHANG Henglei,Marangoni Y R,ZUO Renguang et al.The improved anisotropy normalized variance for detecting non-vertical magnetization anomalies[J].Chinese Journal of Geophysics,2014,57(8):2724-2731.
[24] 周文纳,杜晓娟,李吉焱.重力数据的平面全张量梯度角度边界识别方法[J].石油地球物理勘探,2013,48(6):1009-1015.ZHOU Wenna,DU Xiaojuan,LI Jiyan.Gravity data edge identification using plane full tensor gradient angle[J].Oil Geophysical Prospecting,2013,48(6):1009-1015.
[25] 王万银.位场总水平导数极值位置空间变化规律研究[J].地球物理学报.2010,53(9):2257-2270.WANG Wanyin.Spatial variation law of the extreme value positions of total horizontal derivative for potential field data[J].Chinese Journal of Geophysics,2010,53(9):2257-2270.