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1.
应用地震资料约束下大地电磁资料反演古潜山或基底内部结构的新方法. 首先利用地震及井资料,反演得到古潜山或基底之上各层的厚度及电阻率,建立了古潜山或基底以上的地电模型;并利用大地电磁一维反演资料,建立了古潜山或基底及其以下的地电模型. 在初始模型建立的基础上,应用高效快速的二维大地电磁正演算法——模式匹配方法,进行正演计算. 利用共扼梯度迭代方法,进行正反演迭代计算. 通过对胜利油田南北618剖面反演, 基底以下在地震资料没有显示的构造信息,在反演结果中得到了较好地反映. 相似文献
2.
稀疏测线大地电磁资料三维反演研究:合成算例(英文) 总被引：2，自引：1，他引：1
受勘探成本和工区环境等因素的影响,当前大多数大地电磁实际工作采取布置稀疏测线采集数据和使用二维反演方法解释这些稀疏测线数据的方式。然而,二维反演方法在解释三维地电构造数据时存在局限性,有时甚至做出错误的地质解释。本文尝试了使用三维反演方法对大地电磁稀疏测线数据进行反演解释。使用大地电磁全信息资料三维共轭梯度反演程序对理论模型合成稀疏测线数据进行了三维反演。结果表明:这种反演方案是可行与有效的。同时,我们发现在不同数据的三维反演结果中,四个张量阻抗元素和两个倾子数据同时反演的结果相对更为准确,更接近理论模型。 相似文献
3.
在已有研究成果的基础上,为了适应物性参数剧烈变化的复杂模型并满足联合反演的要求,开发了速度和电阻率随机分布共网格单元模型的建模技术.基于这种统一的物性随机分布的网格介质模型,利用有限元方法和改进的射线追踪法分别正演计算大地电磁场和地震走时,结合改进的模拟退火算法,研究实现了电阻率和速度随机分布条件下的大地电磁与地震资料的同步联合反演.对物性界面不完全一致和物性变化剧烈的带地形复杂模型的试验,表明了该方法在精细反演复杂电阻率和速度结构方面的效果,克服了以往研究局限于简单模型的不足.对地震资料品质差的地区开展的实际资料联合反演,表明了方法的适用性,先验信息约束下的联合反演提高了反演精度. 相似文献
4.
Franco Macchioli-Grande Fabio Zyserman Leonardo Monachesi Laurence Jouniaux Marina Rosas-Carbajal 《Geophysical Prospecting》2020,68(5):1633-1656
In glacial studies, properties such as glacier thickness and the basement permeability and porosity are key to understand the hydrological and mechanical behaviour of the system. The seismoelectric method could potentially be used to determine key properties of glacial environments. Here we analytically model the generation of seismic and seismoelectric signals by means of a shear horizontal seismic wave source on top of a glacier overlying a porous basement. Considering a one-dimensional setting, we compute the seismic waves and the electrokinetically induced electric field. We then analyse the sensitivity of the seismic and electromagnetic data to relevant model parameters, namely depth of the glacier bottom, porosity, permeability, shear modulus and saturating water salinity of the glacier basement. Moreover, we study the possibility of inferring these key parameters from a set of very low noise synthetic data, adopting a Bayesian framework to pay particular attention to the uncertainty of the model parameters mentioned above. We tackle the resolution of the probabilistic inverse problem with two strategies: (1) we compute the marginal posterior distributions of each model parameter solving multidimensional integrals numerically and (2) we use a Markov chain Monte Carlo algorithm to retrieve a collection of model parameters that follows the posterior probability density function of the model parameters, given the synthetic data set. Both methodologies are able to obtain the marginal distributions of the parameters and estimate their mean and standard deviation. The Markov chain Monte Carlo algorithm performs better in terms of numerical stability and number of iterations needed to characterize the distributions. The inversion of seismic data alone is not able to constrain the values of porosity and permeability further than the prior distribution. In turn, the inversion of the electric data alone, and the joint inversion of seismic and electric data are useful to constrain these parameters as well as other glacial system properties. Furthermore, the joint inversion reduces the uncertainty of the model parameters estimates and provides more accurate results. 相似文献
5.
Marina G. Persova Yuri G. Soloveichik Denis V. Vagin Dmitry S. Kiselev Alexander M. Grif Yulia I. Koshkina Anastasia P. Sivenkova 《Geophysical Prospecting》2020,68(7):2217-2253
We propose the approach to 3D inversion of airborne electromagnetic data, which is intended for discovering subvertical bodies overlapped by essentially inhomogeneous conductive layers. The approach is based on the geometric inversion in which a geoelectrical medium is parameterized with the use of block structures. During the inversion, the coordinates of the borders between the blocks and the rows of the blocks as well as resistivities inside them are determined. In order to solve the forward problem of the airborne electromagnetic survey, we use the non-conforming optimized mesh with the hexahedral cells, which enables us to reduce the number of degrees of freedom and smoothly approximate the curved borders of a geological medium. For a more reliable discovery of subvertical objects, we propose to carry out 3D inversions at several rotations of block structures relative to the flight lines. The workability of this approach is demonstrated using the data which are synthesized for complex geoelectrical models with topography, inhomogeneous overlapping layers and target subvertical bodies oriented differently relative to the flight lines. The results of this investigation show that, in some way or other, the elongated subvertical object is discovered and its orientation (the direction of its long side) is defined at different rotations of block structures used in 3D inversions. However, the most accurate recovery of the subvertical object length is achieved when the direction of its long side almost coincides with the direction of one of the block structures axes. Thus, the block structures rotations allow not only more reliably discovering a target object in complex geoelectrical conditions, but also more exactly defining its orientation and length. 相似文献
6.
Many joint inversion schemes use 1D forward modelling in the integrated interpretation of various geophysical data. In extending the joint inversion approach to the investigation of 2D structures, the discretization of the model parameters and the appropriate choice of the forward‐modelling procedure play a very important role. In this paper, a hybrid seismic–geoelectric joint inversion method is proposed for the investigation of 2D near‐surface geological structures. The electric and seismic models are coupled together through the use of common boundaries between the adjacent layers. Assuming a 2D model composed of homogeneous layers with curved boundaries, a fast ray‐tracing algorithm is used for the calculation of refraction seismic traveltime data. In the geoelectric forward modelling, a locally 1D approximation is used. The boundary surfaces are written in the form of series expansion; the inversion algorithms are formulated for the expansion coefficients and the petrophysical parameters as unknowns. Two versions of the inversion method are proposed: in versions A and B, interval‐wise constant functions and Chebyshev polynomials are, respectively, used as basis functions of the series expansion. The versions are tested by means of synthetic and in situ measured data. The tests show that both methods are stable and accurate. 相似文献
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8.
可控源音频大地电磁法(CSAMT)一直沿用大地电磁法(MT)的办法,通过计算电场分量与磁场分量的比值,求取卡尼亚视电阻率.而CSAMT场源已知,电场分量和磁场分量都与地下电阻率存在一定的关系,可以单独采用CSAMT电场分量或者磁场分量提取地下介质的视电阻率.本文通过分析电场分量与磁场分量的数据特性,提出利用CSAMT电场单分量数据进行视电阻率的计算,用改进的广义逆矩阵反演方法,使初始模型中的地电层数等于频道个数,克服了以往反演计算中层数较少的问题;实现全场区电场分量视电阻率曲线的拟合反演.同时对单分量视相位计算方法进行分析,结合山西大同地区积水采空区探测及数据解释结果,论证本文提出的单分量解释方法的有效性. 相似文献
9.
Mohammad Israil 《Acta Geophysica》2006,54(2):126-141
Two techniques have been presented for the delineation of boundaries from smooth models obtained by smooth inversion techniques
of geoelectrical sounding data, such as straightforward inversion scheme, Occam’s and Zohdy’s methods. The smooth model consists
of a large number of equally spaced layers, wherein the real geological boundaries are missing. The techniques proposed here
suppress the geologically irrelevant boundaries and support the real structural boundaries present in the geoelectrical data.
In the first technique, solution of linear inverse problem is improved iteratively through weighted minimum norm inverse,
the weight being taken from the current solution. The technique is referred as Iterative Straightforward Inversion Scheme.
The second method is analytical, based on the application of smoothing filter, referred in the literature as edge-preserving
smoothing. A few examples of theoretical magnetotelluric, dc resistivity and field sounding data have been presented to demonstrate
the capabilities of the techniques. The methodologies also reduce the conspicuous oscillations in the smooth solutions caused
by the conversion of sharp boundaries to the smooth ones. 相似文献
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为推进大地电磁三维反演的实用化,本文实现了基于L-BFGS算法的带地形大地电磁三维反演.首先推导了大地电磁法三维反演的Tikhonov正则化目标函数以及Hessian矩阵逆矩阵近似表达式和计算方法,然后设计了一种既能保证空气电阻率固定不变又能保证模型平滑约束的协方差矩阵统一表达式,解决带地形反演问题.在反演算法中采用正则化因子冷却法以及基于Wolf条件的步长搜索策略,提升了反演的稳定性.利用开发的算法对多个带地形地电模型（山峰地形下的单个异常模型、峰-谷地形下的棋盘模型）的合成数据进行了三维反演,并与已有大地电磁三维反演程序（ModEM）进行对比,验证了本文开发的三维反演算法的正确性和可靠性.最后,利用该算法反演了华南某山区大地电磁实测数据,得到该区三维电性结构,揭示了研究区以高阻介质为基底,中间以低阻不整合面和相对低阻介质连续分布,浅部覆盖高阻介质的电性结构特征,进一步验证了本文算法的实用性. 相似文献
12.
M. S. Zhdanov V. I. Dmitriev A. V. Gribenko 《Izvestiya Physics of the Solid Earth》2010,46(8):655-669
The problem of quantitative three-dimensional interpretation of the magnetotelluric (MT) data ranks among the most difficult
problems in electromagnetic (EM) geophysics. Our paper presents a new rigorous numerical method for MT inversion, based on
the integral equations technique. An important feature of the proposed method is the calculation of the Frechet derivative
with the aid of a quasi-analytical approximation with an inhomogeneous background. This approach simplifies the algorithm
of inversion and requires only a single forward modeling on each iteration. We have also developed a method for a joint inversion
of MT and magnetovariational (MV) data. We show in the present paper that the joint inversion of MT impedances and the Wiese-Parkinson
vectors can automatically allow for the static shift in the observed data, which is caused by the geoelectric inhomogeneities
contained in the near-surface layer. 相似文献
13.
大地电磁的反演问题是非线性,如果采用线性反演方法容易陷入局部极小,使得反演结果非唯一性严重.本文将人工鱼群算法引入到地球物理反演之中,提出了非线性的大地电磁人工鱼群最优化反演.该方法不需要进行偏导数的求取,可以对反演的范围进行约束,以减小反演结果的非唯一性.同时我们对搜索步长进行了改进,给出适用于大地电磁反演的人工鱼群参数.大量的理论数据试算表明,人工鱼群反演算法能够较好地寻找到全局最优解.实测数据的处理结果表明,该方法可以用来处理实际资料,并且能够取得很好的应用效果. 相似文献
14.
可控源音频大地电磁法在资源勘探等领域中发挥着重要的作用.我们把有限差分数值模拟方法用于可控源音频大地电磁三维正演,结合正则化反演方案和共轭梯度反演的思路,将反演中的雅可比矩阵计算问题转为求解两次"拟正演"问题,得到模型参数的更新步长,形成反演迭代,实现了可控源音频大地电磁三维共轭梯度反演算法.该反演算法可用于对有限长度电偶源激发下采集到的可控源音频大地电磁全区(近区、过渡区和远区)视电阻率和相位资料进行三维反演定量解释,获得地下三维模型的电阻率结构.理论模型合成数据的反演算例验证了所实现的可控源音频大地电磁三维共轭梯度反演算法的有效性和稳定性. 相似文献
15.
The magnetotelluric （MT） method has been among the favorite supporting tools for seismic imaging of sub-salt and sub-basalt targets. In this paper we present an example from Kachchh, India （where basaltic rocks overlie Mesozoic sedimentary rocks）, and discuss the feasibility of using MT method as an exploration tool in this geological setting. Our results highlight the difference in magnetotelluric response caused by the thin intrabasalt layering. The key issue addressed in this paper is what MT can and cannot provide in such geological settings. First, we compute apparent resistivity and phase response curves using representative resistivity-depth models and borehole data from the study area. Later, we compare these results to assess the plausibility of using MT to image the sub-volcanic sediments at Kachchh. Finally, we substantiate our discussion through one-dimensional inversion of the field observed MT data from this region that exhibits poor sensitivity of MT for thin basalt layers. 相似文献
16.
Due to the influence of volcanic rock or weathering crust coverage, the quality of deep seismic data is often not reliable and it is difficult to identify small deep buried hill structure beneath the cover. However, the gravity exploration technology can use the remarkable density differences between the object and the overlying strata to identify this special geological reservoir. Although recently several rounds of seismic exploration have been carried out in Raoyang depression, Huabei Oilfield, North China to determine the existence of Hu 8 north deep buried hill, whether the buried hill really exists or not as well as its scale is still in controversial. In this paper, based on the information of seismic data and formation density, deep processing of 3D high precision ground gravity data has been carried out for 3D forward and inversion computation. The dimensional gravity forward calculation results show that the density of the deep anomaly body forms a relatively low gravity anomaly in the earth's surface. By using the potential processing method of vertical second derivative, and sliding filtering, the residual anomaly is separated from regional or background field, which illustrates the existence of a local high gravity anomaly at Hu 8 north area. According to the amplitude of residual gravity anomaly and formation density difference modeling, through a number of 3D forward calculations and 3D inversion of gravity data, the existence of Hu 8 north buried hill and its possible scale are basically determined. The results prove that the 3D high precision gravity method is effective in determining the deep buried hill structure in case that seismic data is not reliable. 相似文献
17.
基于传播矩阵理论开发砂泥岩薄互层地震合成记录算法,与褶积算法、基于界面模型的Zoeppritz方法以及波动方程等方法相比,该方法更适用于具有复杂结构的薄互层模型,能够在充分考虑地震反射波动力学因素的同时不受网格间距的限制.基于正演算法开发了基于波形对比的砂泥岩薄互层地震反演技术,由地震反射波形特征的变化反演薄地层单元中砂体含量与空间位置等参数,进而确定薄互层段砂泥岩组合结构以及砂体的空间展布.理论模型验证了反演方法的有效性.通过测井分析建立薄互层地震地质模型,并将该技术应用于研究区实际地震数据,反演的砂体空间分布与测井资料进行对比分析,验证了反演方法的实用性. 相似文献
18.
针对大地电磁正则化反演中正则化因子的选取困难问题提出了自适应正则化反演算法（Adaptive Regularized Inversion Algorithm, ARIA）. 在该算法中， ①提出了一种新的数据方差处理方法：数据方差规范化，使得数据方差的大小只对数据的拟合发生影响，不对数据目标函数和模型约束目标函数的权重产生影响，从而减少了正则化因子取值的影响因素；②提出了粗糙度核矩阵的概念，并给出了由基本结构插值基函数计算粗糙度核矩阵的公式，使得模型目标函数的构建更为简便、直接；③根据数据目标函数、模型约束目标函数和正则化因子之间的关系，提出了两种正则化因子自适应调节方法. 本文详细阐述了最平缓模型约束下的大地电磁一维连续介质反演的ARIA实现，以几个算例的分析比较来说明ARIA的有效性. 相似文献
19.
Yan-Ling Shi Zu-Zhi Hu Wen-Hui Huang Qiang Wei Sheng Zhang Cui-Xian Meng Lian-Sheng Ji 《应用地球物理》2016,13(3):469-479
The coal-bearing strata of the deep Upper Paleozoic in the GS Sag have high hydrocarbon potential. Because of the absence of seismic data, we use electromagnetic (MT) and gravity data jointly to delineate the distribution of deep targets based on well logging and geological data. First, a preliminary geological model is established by using three-dimensional (3D) MT inversion results. Second, using the formation density and gravity anomalies, the preliminary geological model is modified by interactive inversion of the gravity data. Then, we conduct MT-constrained inversion based on the modified model to obtain an optimal geological model until the deviations at all stations are minimized. Finally, the geological model and a seismic profile in the middle of the sag is analysed. We determine that the deep reflections of the seismic profile correspond to the Upper Paleozoic that reaches thickness up to 800 m. The processing of field data suggests that the joint MT–gravity modeling and constrained inversion can reduce the multiple solutions for single geophysical data and thus improve the recognition of deep formations. The MT-constrained inversion is consistent with the geological features in the seismic section. This suggests that the joint MT and gravity modeling and constrained inversion can be used to delineate deep targets in similar basins. 相似文献
20.
针对重力与地震联合反演存在的问题,结合已有的研究成果,本文研究实现了速度和密度随机分布共网格单元模型的建模技术,以适应密度和速度剧烈变化的复杂模型及联合反演的计算要求.重力正演利用了该网格的二度半体模型,并进一步改进了地震走时的二维射线追踪计算方法,以适用于速度随机分布的网格介质.结合改进的模拟退火算法,实现了这种共网格条件下的重力与地震资料的同步联合反演.模型试验证明了重力与地震联合反演可以准确确定复杂物性界面的密度和速度结构,适用于物性界面不完全一致和物性变化剧烈的复杂模型,并且联合反演结果要优于单独的重力反演.带先验信息约束下的实际资料的联合反演,进一步证明了该方法的适用性和效果,可提高反演精度并减少多解性. 相似文献