共查询到19条相似文献，搜索用时 187 毫秒
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将场源区剖分成长方体单元,通过采集的重磁数据反演出这些单元的密度或者磁化率变化,勾画出场源的分布图像,这种方式是重磁三维反演的重要方向.重磁相关成像通过计算测量的重磁异常与地下各点在测区上的重磁异常的归一化相关,显示出异常地质体的空间赋存状态和等效剩余重磁物性.该方法计算速度快,方法简单、稳定,但是反演的结果只是在-1到+1之间的等效物性,不能够直接反演剩余密度或者磁化率,并且无法引入已知的地质约束.本文通过对物性模型的正演和实测结果的残差进行相关成像,迭代更新物性模型实现对物性参数的反演过程.模型实验证明该方法相对相关成像不仅能提高分辨率,还能够得到真正的物性参数. 相似文献
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2D磁异常分步反演方法是利用二维(剖面)磁测数据确定场源几何参数以及物性参数的一种反演方法,该方法的优点是构造的形态函数S不受场源磁化特征的影响,因此可以在未知场源物性参数的前提下,通过拟合依次反演得到磁性源形体横截面几何参数、磁化强度以及磁化方向.本文阐述了2D磁异常分步反演方法的原理及步骤,对形态函数S的特征及求取方法进行了讨论,分析了区域背景干扰(正常场)对反演结果的影响并提出了初步解决方案.在方法研究的基础上,进行了单一理论模型及组合理论模型的试算,得到了较好的反演结果.为了验证该方法的效果,对实测剖面进行了试算,得到了场源的边界及场源埋深信息,为进一步反演提供了有用的参考. 相似文献
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谱矩方法可以对数据的表面形貌做较为细致的描述.它以随机过程为理论基础,用各阶谱矩及统计不变量等具体的参数表征表面的几何形态,算术平均顶点曲率是一种基于四阶谱矩的统计不变量.通常,埋深不同的场源所引起的磁异常尺度不同,从曲率的角度来理解即为磁异常曲面的弯曲程度不同.因此,本文应用算术平均顶点曲率提取磁异常的几何信息,并将所提取的信息用于场源深度的反演.理论上推导了基于谱矩的球状磁源体和板状磁源体的反演公式,得到了场源深度与磁异常、曲率之间的关系式.结合理论模型计算验证了方法的有效性,并与欧拉反褶积方法进行对比.与传统的方法相比,该方法快速简单,无需调节参数,且有较好的反演精度.最后,将该方法用于塔里木盆地航磁异常的反演和解释中,反演出的磁源体深度可满足区域磁异常数据分析和解释的要求,为克拉通沉积盆地磁异常源的深度划分提供丰富的信息. 相似文献
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在磁异常数据处理中,利用等效源技术重构磁异常场具有较好的稳定性和较高的计算精度,因而被广泛应用.传统方法是采用设置在近地表的单层等效源拟合实测磁异常数据,尽管拟合精度很高,但向上延拓之后往往会出现较大的拟合误差,即可能存在磁异常信号的"泄漏",尤其在原始数据中存在背景场时更容易出现此种误差.本文提出一种多层等效源技术方案,应用分布于不同深度范围内的等效源模拟实测数据,减少了等效源参数设置的盲目性.理论模型试验表明,采用多层等效源方法重构的磁异常及其梯度与分量,较单层等效源方法具有更高精度,可以吸收更完整的实测磁异常信息.论文详细地讨论了如何优化多层等效源设置、等效源参数选择以及计算方法,通过二维和三维理论模型试验,验证了在复杂条件下多层等效源方法的可行性和适应性,并且将该方法应用于广西某地的实测磁异常数据转换之中,取得了较好的应用效果. 相似文献
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化极转换是磁异常解释的重要基础,为了克服在地磁纬度较低的地区尤其是磁赤道附近化极不稳定的问题,出现了多种化极方法．本文基于概率成像技术提出了一种等效物性的反演方法,实现对地下等效场源的反演成像,取得了对低纬度磁异常稳定化极的效果．化极反演中逐次对剩余异常进行反演成像,实现由概率模型到物性模型的复杂映射,避免了类似反演中需要大型方程组求解等问题,并将概率模型的构制、物性参数的反演和反演评价有机地集成到一起,加速了反演成像的进程,使反演成像速度与目前概率成像的计算速度达到可相比拟的程度．对理论模型和实际资料的计算表明,该方法对低纬度磁异常化极处理是稳定有效的,而且可以较好地压制噪声干扰,能够在噪声干扰条件下进行反演化极． 相似文献
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Theta图是利用位场(重磁)数据识别边界的常用方法,其表达式为重磁异常水平变化与垂直变化的比值函数.该方法计算浅源地质体边界的效果较好,而由于深源位场数据在换算过程中会产生趋同效应,在深源地质体识别应用中计算结果不准确,为此,本文提出Theta-Depth法并进行地质体埋深的计算.首先给出直接利用Theta图像进行场源体深度估算的方法,然后推导出基于Theta导数的线性方程来自动估算场源位置参数,本文方法可有效地利用Theta图像的特征为约束条件来提高反演结果的精度.理论模型试验证明本文提出的Theta-Depth法能有效地计算出场源体位置和深度.将该方法应用于满都拉地区实测磁数据的解释,帮助圈定了矿脉的分布. 相似文献
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将地下场源区域规则划分成很多小长方体单元，并且通过反演确定这些单元的物性变 化，勾画出场源的分布图像，这种方式逐步成为重磁反演，特别是三维反演的重要方向；遗 传算法等非线性技术进行该类反演将逐步成为发展趋势. 本文指出，在应用遗传算法进行该 类反演过程中，隐含着数据量较大时超常规的计算量，它已成为制约该类反演充分发挥作用 的瓶颈问题；同时，本文提出了针对性的分离并存储几何格架的计算策略、以及独特的几何 格架等效压缩存储技术，可以从根本上提高非线性反演计算速度，为该类反演的有效应用奠 定了坚实的基础. 相似文献
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垂直线电流源的三维电阻率成像 总被引：5，自引：0，他引：5
在油井注水和深井注浆的电法监测中,地表布设平面的电位测量网,而将钻井的钢套管作为线电流源来供电,据此可确定流体的运动方向和分布特征.数据处理中需解决垂直线电流源的三维电阻率反演.本文叙述了相应的反演理论和偏导数计算方法.在某油田的试验中,以生产井为电极圈的中心,每圈均匀布设18个电极,共6圈,在地表得到了108个电位数据,获得500～2 000m之间5个不同深度层的真电阻率分布图像,并对深度层为1 500～1 600m的图像进行了初步解释.结果表明,该方法可以对井下某深度层中的流体运动和分布可进行有效的监测. 相似文献
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为了实现曲面随机点位场数据的曲面延拓和转换,以磁异常位场数据为例,采用一组磁偶极子作为等效源,置于观测面下方的一个曲面上,把观测磁异常作为这组磁偶极子所产生磁异常的边界条件,通过求解线性方程组的方法反演磁偶极子磁矩的大小,再根据反演结果正演所要计算的磁异常数据,实现了曲面随机点磁异常位场数据的向上延拓、向下延拓、求导以及化极处理.在数据量较大时,为了提高反演计算的速度,把磁异常数据和磁偶极子分成若干小块,再利用各块磁异常数据分别反演该块数据下方磁偶极子的磁矩,并通过迭代计算来逐步取得更准确的反演结果.模型试验表明,磁异常位场数据向上延拓的均方根误差小于±2nT,向下延拓和化极也可以取得较高的精度,所提出的分块处理方法提高了延拓和转换的速度,实际资料处理给出了曲面随机点航磁异常数据向下延拓和化极的一个例子. 相似文献
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Elimination of the water-layer response from multi-component source and receiver marine electromagnetic data 总被引：1，自引：0，他引：1
Janniche Iren Nordskag Lasse Amundsen Lars Løseth Egil Holvik 《Geophysical Prospecting》2009,57(5):897-918
This paper presents the theory to eliminate from the recorded multi‐component source, multi‐component receiver marine electromagnetic measurements the effect of the physical source radiation pattern and the scattering response of the water‐layer. The multi‐component sources are assumed to be orthogonally aligned above the receivers at the seabottom. Other than the position of the sources, no source characteristics are required. The integral equation method, which for short is denoted by Lorentz water‐layer elimination, follows from Lorentz' reciprocity theorem. It requires information only of the electromagnetic parameters at the receiver level to decompose the electromagnetic measurements into upgoing and downgoing constituents. Lorentz water‐layer elimination replaces the water layer with a homogeneous half‐space with properties equal to those of the sea‐bed. The source is redatumed to the receiver depth. When the subsurface is arbitrary anisotropic but horizontally layered, the Lorentz water‐layer elimination scheme greatly simplifies and can be implemented as deterministic multi‐component source, multi‐component receiver multidimensional deconvolution of common source gathers. The Lorentz deconvolved data can be further decomposed into scattering responses that would be recorded from idealized transverse electric and transverse magnetic mode sources and receivers. This combined electromagnetic field decomposition on the source and receiver side gives data equivalent to data from a hypothetical survey with the water‐layer absent, with idealized single component transverse electric and transverse magnetic mode sources and idealized single component transverse electric and transverse magnetic mode receivers. When the subsurface is isotropic or transverse isotropic and horizontally layered, the Lorentz deconvolution decouples into pure transverse electric and transverse magnetic mode data processing problems, where a scalar field formulation of the multidimensional Lorentz deconvolution is sufficient. In this case single‐component source data are sufficient to eliminate the water‐layer effect. We demonstrate the Lorentz deconvolution by using numerically modeled data over a simple isotropic layered model illustrating controlled‐source electromagnetic hydrocarbon exploration. In shallow water there is a decrease in controlled‐source electromagnetic sensitivity to thin resistors at depth. The Lorentz deconvolution scheme is designed to overcome this effect by eliminating the water‐layer scattering, including the field's interaction with air. 相似文献
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本文提出了能提高异常体分辨能力,同时得到绝对电导率的地面磁电阻率数据三维反演方法.磁电阻率响应用准直流的低频磁场代替;数值模拟由频率域电场满足的Helmholtz方程出发,采用三维交错网格有限差分法;长直导线源作为发射源,其中源的计算包含在背景场中;结合地面磁电阻率数据各分量的特点,选择y分量进行反演研究;反演采用三维非线性共轭梯度反演技术,为了提高异常体的深度分辨能力,进行迭代重构反演;用印模法对初始模型进行重构,采用的是辅模型在浅部,元模型在深部的组合方式.从合成数据和实际数据的反演结果可以得到以下的认识:(1)由频率域麦克斯韦方程组出发,低频磁场数据反演可以直接得到电导率,而不是相对电导率之比;(2)采用印模法组合初始模型,进行迭代重构反演,可以提高地面磁电阻率数据反演对异常体的分辨能力,确定埋深位置,同时不会丧失对于浅部异常体的分辨能力;(3)在结合印模法的地面磁电阻率数据三维反演中,深部异常体的分辨能力受地表不均匀导电体影响较小;(4)确定印模深度可以采用上一次重构反演结束时的模型变化量,通过相邻两次重构反演结束时的模型变化量之差来确定迭代重构是否终止.因为静磁场与重力场在数学上的相似性,本文的反演方法可以被运用到重力场等位场的地面数据的反演中. 相似文献
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Inversion of potential field data using the structural index as weighting function rate decay 总被引：1，自引：0，他引：1
Nonparametric inverse methods provide a general framework for solving potential‐field problems. The use of weighted norms leads to a general regularization problem of Tikhonov form. We present an alternative procedure to estimate the source susceptibility distribution from potential field measurements exploiting inversion methods by means of a flexible depth‐weighting function in the Tikhonov formulation. Our approach improves the formulation proposed by Li and Oldenburg (1996, 1998) , differing significantly in the definition of the depth‐weighting function. In our formalism the depth weighting function is associated not to the field decay of a single block (which can be representative of just a part of the source) but to the field decay of the whole source, thus implying that the data inversion is independent on the cell shape. So, in our procedure, the depth‐weighting function is not given with a fixed exponent but with the structural index N of the source as the exponent. Differently than previous methods, our choice gives a substantial objectivity to the form of the depth‐weighting function and to the consequent solutions. The allowed values for the exponent of the depth‐weighting function depend on the range of N for sources: 0 ≤N≤ 3 (magnetic case). The analysis regarding the cases of simple sources such as dipoles, dipole lines, dykes or contacts, validate our hypothesis. The study of a complex synthetic case also proves that the depth‐weighting decay cannot be necessarily assumed as equal to 3. Moreover it should not be kept constant for multi‐source models but should instead depend on the structural indices of the different sources. In this way we are able to successfully invert the magnetic data of the Vulture area, Southern Italy. An original aspect of the proposed inversion scheme is that it brings an explicit link between two widely used types of interpretation methods, namely those assuming homogeneous fields, such as Euler deconvolution or depth from extreme points transformation and the inversion under the Tikhonov‐form including a depth‐weighting function. The availability of further constraints, from drillings or known geology, will definitely improve the quality of the solution. 相似文献
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Imaging magnetic sources using Euler's equation 总被引：3，自引：0，他引：3
Shu&#;Kun Hsu 《Geophysical Prospecting》2002,50(1):15-25
The conventional Euler deconvolution method has the advantage of being independent of magnetization parameters in locating magnetic sources and estimating their corresponding depths. However, this method has the disadvantage that a suitable structural index must be chosen, which may cause spatial diffusion of the Euler solutions and bias in the estimation of depths to the magnetic sources. This problem becomes more serious when interfering anomalies exist. The interpretation of the Euler depth solutions is effectively related to the model adopted, and different models may have different structural indices. Therefore, I suggest a combined inversion for the structural index and the source location from the Euler deconvolution, by using only the derivatives of the magnetic anomalies. This approach considerably reduces the diffusion problem of the location and depth solutions. Consequently, by averaging the clustered solutions satisfying a given criterion for the solutions, we can image the depths and attributes (or types) of the causative magnetic sources. Magnetic anomalies acquired offshore northern Taiwan are used to test the applicability of the proposed method. 相似文献
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利用重力异常揭示地壳三维密度结构是重力资料地质解释的目标和任务,密度反演的好坏至关重要.本文对华北克拉通进行了重力异常多尺度密度反演研究,首先利用小波变换对重力异常进行多尺度分解,接着利用功率谱分析方法估算各层场源的平均深度,然后利用广义密度反演方法进行各层密度反演,对华北地区进行了多层密度反演,得到其密度结构,并进行地质解释和油气藏分析.结果显示了重力场多尺度密度反演方法的有效性,对华北地区密度结构的地质含义进行了初步分析,位于造山带中的低密度异常主要反映沿造山带展布的花岗岩体.对比华北东部区浅层密度扰动与油气坳陷位置,发现油气坳陷都表现为低幅度的低密度异常区.说明利用小波多尺度反演提取的密度信息对油气勘探的部署有一定指导意义. 相似文献
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Euler deconvolution of the analytic signal and its application to magnetic interpretation 总被引：2，自引：0，他引：2
Euler deconvolution and the analytic signal are both used for semi‐automatic interpretation of magnetic data. They are used mostly to delineate contacts and obtain rapid source depth estimates. For Euler deconvolution, the quality of the depth estimation depends mainly on the choice of the proper structural index, which is a function of the geometry of the causative bodies. Euler deconvolution applies only to functions that are homogeneous. This is the case for the magnetic field due to contacts, thin dikes and poles. Fortunately, many complex geological structures can be approximated by these simple geometries. In practice, the Euler equation is also solved for a background regional field. For the analytic signal, the model used is generally a contact, although other models, such as a thin dike, can be considered. It can be shown that if a function is homogeneous, its analytic signal is also homogeneous. Deconvolution of the analytic signal is then equivalent to Euler deconvolution of the magnetic field with a background field. However, computation of the analytic signal effectively removes the background field from the data. Consequently, it is possible to solve for both the source location and structural index. Once these parameters are determined, the local dip and the susceptibility contrast can be determined from relationships between the analytic signal and the orthogonal gradients of the magnetic field. The major advantage of this technique is that it allows the automatic identification of the type of source. Implementation of this approach is demonstrated for recent high‐resolution survey data from an Archean granite‐greenstone terrane in northern Ontario, Canada. 相似文献
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This paper presents a new inversion method for the interpretation of 2D magnetic anomaly data, which uses the combination of the analytic signal and its total gradient to estimate the depth and the nature (structural index) of an isolated magnetic source. However, our proposed method is sensitive to noise. In order to lower the effect of noise, we apply upward continuation technique to smooth the anomaly. Tests on synthetic noise-free and noise corrupted magnetic data show that the new method can successfully estimate the depth and the nature of the causative source. The practical application of the technique is applied to measured magnetic anomaly data from Jurh area, northeast China, and the inversion results are in agreement with the inversion results from Euler deconvolution of the analytic signal. 相似文献
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为了探索我国海域油气和水合物等高阻目标体CSEM勘探的可行性和方法技术,本文研究了在海水中水平电性源激励下有限水深海洋地电模型的频率域电磁响应,为进一步的1D和3D仿真计算奠定了理论基础.在推导电磁响应公式时,首先给出了各层介质的Lorentz势,然后根据Coulomb势与Lorentz势的关系,得到了各层介质的Coulomb势.各层介质中的电磁场均可以由Lorentz势或者Coulomb势计算得到,但在有限元计算时Coulomb势具有优势.长导线源的电磁场和势函数可以由电偶源的电磁场和势函数沿导线长度积分得到.文中具体给出了海水中水平电偶源和长导线源在海水层的电磁场公式,并根据该公式计算了不同水深环境下海底表面的电磁场分布,分析了海水深度对海底油气储层电磁异常的影响.结果表明,随着水深减小,异常幅度和形态特征发生明显变化.当水深很浅时(如50 m),只有同线方向的Ex和Ez两个电场分量存在明显异常.最后,以两个已知海底油田为例,计算了不同水深环境下可观测到的电场异常,展示了电性源频率域CSEM在海底勘探中(包括浅海环境)的良好应用前景.对于该方法实用化过程中还需进一步解决的问题,文中结尾部分也进行了初步探讨. 相似文献