共查询到20条相似文献，搜索用时 719 毫秒
1.
Norbert Péter Szabó 《Hydrogeology Journal》2018,26(6):1935-1946
An evolutionary inversion approach is suggested for the interpretation of nuclear and resistivity logs measured by direct-push tools in shallow unsaturated sediments. The efficiency of formation evaluation is improved by estimating simultaneously (1) the petrophysical properties that vary rapidly along a drill hole with depth and (2) the zone parameters that can be treated as constant, in one inversion procedure. In the workflow, the fractional volumes of water, air, matrix and clay are estimated in adjacent depths by linearized inversion, whereas the clay and matrix properties are updated using a float-encoded genetic meta-algorithm. The proposed inversion method provides an objective estimate of the zone parameters that appear in the tool response equations applied to solve the forward problem, which can significantly increase the reliability of the petrophysical model as opposed to setting these parameters arbitrarily. The global optimization meta-algorithm not only assures the best fit between the measured and calculated data but also gives a reliable solution, practically independent of the initial model, as laboratory data are unnecessary in the inversion procedure. The feasibility test uses engineering geophysical sounding logs observed in an unsaturated loessy-sandy formation in Hungary. The multi-borehole extension of the inversion technique is developed to determine the petrophysical properties and their estimation errors along a profile of drill holes. The genetic meta-algorithmic inversion method is recommended for hydrogeophysical logging applications of various kinds to automatically extract the volumetric ratios of rock and fluid constituents as well as the most important zone parameters in a reliable inversion procedure. 相似文献
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波阻抗反演中的全局寻优策略 总被引：1，自引：1，他引：1
针对常规基于模型的波阻抗反演方法严重依赖于初始模型的选择和易陷入局部最优等局限性，提出了一种新的全局寻优策略。该反演策略是在常规测井约束反演的框架中加入一定次数的遗传全局搜索机制。如果迭代过程一旦陷入局部最优解；就可以把已经形成的局部最优解作为寻优的新起点，在此基础上进行全局遗传寻优，搜索更优的反演结果。通过模型数值计算和实际资料处理，表明该反演策略具有跳出初始模型控制的优良性能和良好的实际反演效果。 相似文献
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贾善坡 《水文地质工程地质》2012,39(1):31-35
岩土工程优化反分析是一个典型的复杂非线性函数优化问题,采用全局优化算法是解决这个问题的理想途径。结合ABAQUS有限元软件,提出遗传算法与有限元联合反演法,将有限元程序作为一个单独模块嵌入到遗传算法程序中,以测点的实测值与计算值建立误差函数,编制了遗传算法反演分析程序。并给出应用实例验证了该法的有效性,表明该方法可应用于岩土工程中的反演分析工作。 相似文献
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BP神经网络方法在二维密度界面的反演中取得了较好的效果,但在反演三维界面时,由于模型更复杂、参数更多,BP神经网络的收敛速度和反演精度都有一定程度的下降。为了改善反演效果,本文利用遗传算法对BP神经网络的权值、阈值选择过程进行优化,获得了更好的网络模型;并将此模型应用于密度界面模型的反演中,预测误差从上百米减小到数十米,同时迭代计算步数减少了近2/3,有效减少了计算时间,反演结果更准确。利用基于遗传算法优化的BP神经网络反演了法国某地区莫霍面深度,预测相对误差仅为1.8%,取得了较好的应用效果。基于遗传算法优化的BP神经网络在密度界面的反演中具有良好的应用价值和研究前景。 相似文献
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张荣峰 《物探化探计算技术》1996,18(1):67-70
本文用遗传算法（ＧＡ）进行大地电磁测深（ＭＴ）一维模型的反演。本反演方法无需初值，不用求导数，受噪声影响小，能有效克服反演中出现的局部极值，并能给出一组解 相似文献
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基于积分方程法的大地电磁三维反演 总被引：1，自引：0，他引：1
采用积分方程法计算均匀半空间中三维异常体的大地电磁响应,然后利用阻尼最小二乘法反演得到地下三维异常体电阻率分布。在计算灵敏度矩阵时,将灵敏度矩阵分为线性项和体现反演过程非线性的偏微分项进行求解,提高了计算精度。理论模型反演结果表明,反演较准确,对初值依赖性小,且只针对异常体剖分单元进行反演,反演效率较高。 相似文献
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This paper presents a Straightforward Inversion Scheme (SIS) for interpreting one-dimensional magnetotelluric sounding data.
The basic steps of SIS are (i) parameterization of the layered model such that the layer thickness, expressed in units of
its skin depth, is a constant (α); (ii) expansion of the reflection function at each interface as a power series in parameter
u = exp(-2(1 +j)α√f);(iii) development of a recurrence relation between the coefficients of the same powers ofu in the power series of reflection functions of any two successive layers; (iv) estimation of the impedance power series coefficients
using regressed minimum norm estimator; and (v) evaluation of layer resistivities and thicknesses using the inverse recurrence
relation. The power of SIS is established by inverting four synthetic data sets and two field data sets. The effect of noise
is extensively studied on a synthetic data set, deliberately corrupted with increasing levels of Gaussian random noise up
to 25%. It is found that the scheme can retrieve broad features of the true model even with noise levels as high as 25%. On
the basis of findings of different experiments conducted on SIS, it is concluded that SIS is an efficient, robust algorithm
with high resolving power. Further, being linear, it is non-iterative and it dispenses with the requirement of having to choose
an initial guess model. 相似文献
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波阻抗遗传算法反演方法的研究及应用 总被引：3，自引：3，他引：3
作者介绍的遗传算法是在自然界生物遗传过程优选和进化原理的基础上，针对波阻抗反演的实际问题，对标准的遗传算法进行了改进，引入了模拟退火算法中的热槽法控制初始群体的产生，用逐位迭代的交换方式代替传统的杂交方式即随机选择杂交点进行交换。使用改进的遗传算法对地震波阻抗进行反演，可很好地提高反演的精度。在文中最后，作者通过理论模型和实例验证了上述的思想。 相似文献
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利用一维正则化反演进行大地电磁测深数据拟二维反演解释 总被引：1，自引：0，他引：1
大地电磁测深的反演问题是不适定的,其反演结果不稳定,且具有非唯一性。通过在目标函数中采用正则化方法,可以使得不适定反演问题具有稳定的反演结果,并改善解的稳定性和非唯一性问题。为了提高野外大地电磁测深数据的处理效率和初步解释的精度,提出了大地电磁测深数据的一维正则化反演进行拟二维反演解释方法。这里所述的大地电磁测深一维反演解释,与以往的解释方法不同,其思路首先用Bostick反演的深度来控制层参数,使反演计算的模型参数仅存在电阻率;最后采用阻尼高斯-牛顿算法进行反演计算,并将Bostick反演结果作为反演计算的初始模型。通过模型试算,结果表明其处理速度快、解释直观,对野外大地电磁测深数据进行初步反演解释是可行的。 相似文献
12.
Ákos Gyulai Mátyás Krisztián Baracza Norbert Péter Szabó 《Environmental Earth Sciences》2014,71(1):383-392
Geophysical surveying methods are of great importance in environmental exploration. Inversion-based data processing methods are applied for the determination of geometrical and physical parameters of the target model. The use of this geoelectric inversion method is advantageous in environmental research where highly reliable information with large spatial resolution is required. The 2D combined geoelectric inversion (CGI) method performs more accurate parameter estimation than conventional 1D single inversion methods by efficiently decreasing the number of unknowns of the inverse problem (single means that data sets of individual vertical electric sounding stations are inverted separately). The quality improvement in parameter space is demonstrated by comparing the traditional 1D inversion procedure with a 2D series expansion-based inversion technique. The CGI method was further developed by weighting individual direct current geoelectric data sets automatically in order to improve inversion results. The new algorithm was named combined geoelectric weighted inversion, which extracts the solution by a special weighted least squares technique. It is shown that the new inversion methodology is applicable to resolve near-surface structures such as rapidly varying layer boundaries, laterally inhomogeneous formations and pinch-outs. 相似文献
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Qiang Guo Hongbing Zhang Jingbo Tian Lifeng Liang Zuoping Shang 《Arabian Journal of Geosciences》2018,11(3):48
Multiparameter prestack seismic inversion is one of the most powerful techniques in quantitatively estimating subsurface petrophysical properties. However, it remains a challenging problem due to the nonlinearity and ill-posedness of the inversion process. Traditional regularization approach can stabilize the solution but at the cost of smoothing valuable geological boundaries. In addition, compared with linearized optimization methods, global optimization techniques can obtain better results regardless of initial models, especially for multiparameter prestack inversion. However, when solving multiparameter prestack inversion problems, the application of standard global optimization algorithms maybe limited due to the issue of high computational cost (e.g., simulating annealing) or premature convergence (e.g., particle swarm optimization). In this paper, we propose a hybrid optimization-based multiparameter prestack inversion method. In this method, we introduce a prior constraint term featured by multiple regularization functions, intended to preserve layered boundaries of geological formations; in particular, to address the problem of premature convergence existing in standard particle swarm optimization algorithm, we propose a hybrid optimization strategy by hybridizing particle swarm optimization and very fast simulating annealing to solve the nonlinear optimization problem. We demonstrate the effectiveness of the proposed inversion method by conducting synthetic test and field data application, both of which show encouraging results. 相似文献
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全波形反演是一种全新的地震成像方法,主要利用全波形信息反演地下介质参数,通过非线性优化波场理论值和观测值的残差实现波形反演。基于时间域声波方程,建立了时间域波场残差目标函数,以分层模型为例,分别从波场精度、目标函数收敛性和运行时间3个方面,比较了共轭梯度（Conjugate Gradient,CG）算法和拟牛顿算法（Broyden-Fletcher-Goldfarb-Shanno,BFGS）反演的效果。同时,应用共轭梯度法对正、逆断层模型和Marmousi模型进行了速度结构反演。反演结果表明:共轭梯度法计算效率较高,反演得到的速度模型精度更高,反演效果较好,是一种有效的波形反演方法。 相似文献
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In the paper, a novel inversion approach is used for the solution of the problem of factor analysis. The float-encoded genetic algorithm as a global optimization method is implemented to extract factor variables using open-hole logging data. The suggested statistical workflow is used to give a reliable estimate for not only the factors but also the related petrophysical properties in hydrocarbon formations. In the first step, the factor loadings and scores are estimated by Jöreskog’s fast approximate method, which are gradually improved by the genetic algorithm. The forward problem is solved to calculate wireline logs directly from the factor scores. In each generation, the observed and calculated well logs are compared to update the factor population. During the genetic algorithm run, the average fitness of factor populations is maximized to give the best fit between the observed and theoretical data. By using the empirical relation between the first factor and formation shaliness, the shale volume is estimated along the borehole. Permeability as a derived quantity also correlates with the first factor, which allows its determination from an independent source. The estimation results agree well with those of independent deterministic modeling and core measurements. Case studies from Hungary and the USA demonstrate the feasibility of the global optimization based factor analysis, which provides a useful tool for improved reservoir characterization. 相似文献
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Arkoprovo Biswas 《Journal of the Geological Society of India》2016,88(4):493-502
Inversion of self-potential anomaly for 2-D inclined sheets of infinite horizontal extent has been studied. Least-square inversion and very fast simulated annealing global optimization has been used to model the five parameters of self potential anomaly. The method of least square and very fast simulated annealing global optimization method is compared and analyzed. Very fast simulated annealing can model the noisy and field data of self potential anomaly very precisely than linear inversion technique. However, time taken by very fast simulated annealing inversion is larger than linearized inversion. The comparative analysis has been done on synthetic data (noise free and noisy) and two field data from Bavarian woods anomaly, Germany and Surda anomaly, India to show the efficacy of both the methods. The estimated parameters were compared with those from previous studies using various global optimization algorithms, mainly neural network, genetic algorithm and particle swarm optimization on the same field data sets. It can be concluded that the global optimization algorithms considered in this study were able to yield compatible solutions with those from least-square methods. The present global optimization method is in good agreement with the other global optimization methods in terms of results and computation time. 相似文献
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推导了基于角度域共成像点道集的叠前深度偏移层析速度分析公式,提出一种共散射点（CSP）道集与角道集串级优化叠前偏移的速度分析方法。该方法通过基于CSP道集的叠前时间偏移速度分析获取初始速度,利用基于角度域共成像点道集（ADCIGs）的叠前深度偏移速度分析进行速度更新。实现步骤概括为：将叠前地震数据映射为CSP道集,利用CSP道集叠加速度谱拾取能量团获取均方根（RMS）速度场;通过Dix公式将RMS速度转换为层速度作为层析的初始输入速度,基于ADCIGs实现叠前深度偏移层析速度反演,最终得到高精度的叠前偏移速度场。断层模型和实际资料试算结果验证了该方法的正确性和有效性。 相似文献
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非迭代,非线性二维重力反演计算方法 总被引：1，自引：0，他引：1
本文叙述了非迭代、非线性二维重力反演方法的原理、模型计算及应用效果等。与以往诸多的求界面重力反演方法相比,该法的主要特点是：将界面的深度用一幂级数的形式表示,且幂级数系数的计算与界面上下地层的密度差无关。因此,一旦求出了幂级数的系数,由界面的密度差可直接得到界面的深度,且幂级数收敛的速度很快。 相似文献
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冻土的蠕变特性对深井冻结法施工至关重要。针对某矿区人工冻土在-5℃、-10℃、-15℃和-20℃下进行单轴抗压强度试验,发现冻土的抗压强度受冻结温度变化影响,两者间为线性反比例关系。通过小生境原理对传统的遗传算法作模糊随机改进,给出模糊遗传算法的步骤思路,进而运用该算法反演冻土蠕变模型中的参数值,获得各温度下的蠕变模型。试验结果表明：蠕变模型计算值在蠕变各阶段与试验值吻合较好,准确反映了冻土蠕变的整体规律。可见,模糊遗传算法能有效反演蠕变参数,较传统方法更符合工程实际。 相似文献
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为了进一步改进完善核磁共振T2谱反演算法,利用核磁共振正演模拟信号,研究回波间隔、原始回波采集数量、信噪比等因素对反演结果的影响,同时在不同信噪比下对最优化T2谱反演算法、奇异值分解反演算法进行比较分析。研究表明:采集弛豫信号时,回波间隔大小的设置与回波数量、组分大小相匹配,才能得到最佳的反演效果;信噪比越高反演效果越好,当信噪比大于25时反演谱与构造谱基本吻合;在反演不同信噪比理论回波数据时,最优化反演方法对信噪比要求不高,奇异值分解反演方法对信噪比要求高,而奇异值分解反演速度较快。 相似文献