共查询到20条相似文献，搜索用时 47 毫秒
1.
叠前地震反演技术能够将地震中振幅、偏移距和入射角等多种有效信息与油气的敏感参数结合起来,在有效识别油气藏"甜点"方面虽发挥了重要的作用,但对于煤层气的有效预测仍需研究.针对煤层气与石油天然气的赋存地质条件不同,本文以山西沁水盆地煤层气地震资料为例,借鉴叠前地震反演技术的多参数预测思想,通过模型正演和实测资料处理,得到纵波、横波速度和密度等不同的数据体,利用数据体和弹性参数关系式,采用AkiRichard近似公式与叠前宽角度反演联合的方法,寻找出富含煤层气储层的敏感参数.从而实现富含煤层气储层的有效预测.经与测井曲线结果对比,吻合率较高,说明了该方法具有可行性与实用性. 相似文献
2.
提出了各向异性页岩储层统计岩石物理反演方法.通过统计岩石物理模型建立储层物性参数与弹性参数的定量关系,使用测井数据及井中岩石物理反演结果作为先验信息,将地震阻抗数据定量解释为储层物性参数、各向异性参数的空间分布.反演过程在贝叶斯框架下求得储层参数的后验概率密度函数,并从中得到参数的最优估计值及其不确定性的定量描述.在此过程中综合考虑了岩石物理模型对复杂地下介质的描述偏差和地震数据中噪声对反演不确定性的影响.在求取最大后验概率过程中使用模拟退火优化粒子群算法以提高收敛速度和计算准确性.将统计岩石物理技术应用于龙马溪组页岩气储层,得到储层泥质含量、压实指数、孔隙度、裂缝密度等物性,以及各向异性参数的空间分布及相应的不确定性估计,为页岩气储层的定量描述提供依据. 相似文献
3.
孙林洁 《CT理论与应用研究》2020,29(5):566-575
优质气层与低含气饱和度的差气层、气水同层均呈现"亮点"强振幅的地震响应特征,利用振幅类属性或者常规弹性参数难以进行有效判识。考虑到密度参数随含气饱和度的高敏感性,本文在贝叶斯叠前反演框架下,以三变量柯西分布为先验正则约束进行叠前地震反演,减小了纵波速度、横波速度与密度三参数统计相关性造成的参数估算误差,进一步提高了弹性参数的可靠性,模型测试表明新方法反演的密度精度及稳定性更高。将方法应用于马达班湾盆地X区块,在流体替代及岩石物理统计分析的指导下,利用基于三变量柯西分布的叠前地震反演方法提取密度参数,预测优质气层富集区,实钻结果与预测结果吻合度高,表明该方法具有较高的实用性。 相似文献
4.
The Connolly (1999) elastic impedance (EI) equation is a function of P-wave velocity, S-wave velocity, density, and incidence
angle. Conventional inversion methods based on this equation can only extract P-velocity, S-velocity, and density data directly
and the elastic impedance at different incidence angles are not at the same scale, which makes comparison difficult. We propose
a new elastic impedance equation based on the Gray et al. (1999) Zoeppritz approximation using Lamé parameters to address
the conventional inversion method’s deficiencies. This equation has been normalized to unify the elastic impedance dimensions
at different angles and used for inversion. Lamé parameters can be extracted directly from the elastic impedance data obtained
from inversion using the linear relation between Lamé parameters and elastic impedance. The application example shows that
the elastic parameters extracted using this new method are more stable and correct and can recover the reservoir information
very well. The new method is an improvement on the conventional method based on Connolly’s equation.
Wang Baoli graduated with a Bachelor’s degree in Prospecting Information and Engineering from the China University of Petroleum (East
China) in 2004 and earned her Master’s degree from the department of Geophysical Prospecting and Information Technology in
the China University of Petroleum ((East China) in 2006. She now studies for her PhD at the China University of Petroleum
(East China). Her research interest is elastic impedance inversion. 相似文献
5.
用Connolly的弹性阻抗(EI,elastic impedance)公式进行反演只能直接得到纵、横波速度和密度的信息,然后才可间接计算得到纵横波阻抗等其它的参数数据体,这样便增加了一步误差使数据的准确性降低.本文首先针对该方法的这些缺点和不足,提出了以Zoeppritz方程的Fatti近似为基础一种新的弹性阻抗公式,由该公式可得到比用Fatti近似更准确的反射系数,然后对这个公式进行了标准化以实现不同角度的弹性阻抗间量纲的统一,最后用标准化后的公式进行了反演,从反演得到的不同角度的弹性阻抗数据体中可直接提取得到纵横波阻抗数据体.应用实例表明用这种方法提取得到的纵横波阻抗更加稳定、准确,而且能很好地反映储层信息.这种新的方法是对以Connolly公式为基础的传统方法的改进. 相似文献
6.
Cauchy priori distribution-based Bayesian AVO reflectivity inversion may lead to sparse estimates that are sensitive to large reflectivities. For the inversion, the computation of the covariance matrix and regularized terms requires prior estimation of model parameters, which makes the iterative inversion weakly nonlinear. At the same time, the relations among the model parameters are assumed linear. Furthermore, the reflectivities, the results of the inversion, or the elastic parameters with cumulative error recovered by integrating reflectivities are not well suited for detecting hydrocarbons and fuids. In contrast, in Bayesian linear AVO inversion, the elastic parameters can be directly extracted from prestack seismic data without linear assumptions for the model parameters. Considering the advantages of the abovementioned methods, the Bayesian AVO reflectivity inversion process is modified and Cauchy distribution is explored as a prior probability distribution and the time-variant covariance is also considered. Finally, we propose a new method for the weakly nonlinear AVO waveform inversion. Furthermore, the linear assumptions are abandoned and elastic parameters, such as P-wave velocity, S-wave velocity, and density, can be directly recovered from seismic data especially for interfaces with large reflectivities. Numerical analysis demonstrates that all the elastic parameters can be estimated from prestack seismic data even when the signal-to-noise ratio of the seismic data is low. 相似文献
7.
Myung Hoon Kim Yunseok Choi Young Ho Cha Changsoo Shin 《Pure and Applied Geophysics》2009,166(12):1967-1985
In order to correctly interpret marine exploration data, which contain many elastic signals such as S waves, surface waves and converted waves, we have developed both a frequency-domain modeling algorithm for acoustic-elastic coupled media with an irregular interface, and the corresponding waveform inversion algorithm. By applying the continuity condition between acoustic (fluid) and elastic (solid) media, wave propagation can be properly simulated throughout the coupled domain. The arbitrary interface is represented by tessellating square and triangular finite elements. Although the resulting complex impedance matrix generated by finite element methods for the acoustic-elastic coupled wave equation is asymmetric, we can exploit the usual back-propagation algorithm used in the frequency domain through modern sparse matrix technology. By running numerical experiments on a synthetic model, we demonstrate that our inversion algorithm can successfully recover P- and S-wave velocity and density models from marine exploration data (pressure data only). 相似文献
8.
In geophysical inverse problems, the posterior model can be analytically assessed only in case of linear forward operators, Gaussian, Gaussian mixture, or generalized Gaussian prior models, continuous model properties, and Gaussian-distributed noise contaminating the observed data. For this reason, one of the major challenges of seismic inversion is to derive reliable uncertainty appraisals in cases of complex prior models, non-linear forward operators and mixed discrete-continuous model parameters. We present two amplitude versus angle inversion strategies for the joint estimation of elastic properties and litho-fluid facies from pre-stack seismic data in case of non-parametric mixture prior distributions and non-linear forward modellings. The first strategy is a two-dimensional target-oriented inversion that inverts the amplitude versus angle responses of the target reflections by adopting the single-interface full Zoeppritz equations. The second is an interval-oriented approach that inverts the pre-stack seismic responses along a given time interval using a one-dimensional convolutional forward modelling still based on the Zoeppritz equations. In both approaches, the model vector includes the facies sequence and the elastic properties of P-wave velocity, S-wave velocity and density. The distribution of the elastic properties at each common-mid-point location (for the target-oriented approach) or at each time-sample position (for the time-interval approach) is assumed to be multimodal with as many modes as the number of litho-fluid facies considered. In this context, an analytical expression of the posterior model is no more available. For this reason, we adopt a Markov chain Monte Carlo algorithm to numerically evaluate the posterior uncertainties. With the aim of speeding up the convergence of the probabilistic sampling, we adopt a specific recipe that includes multiple chains, a parallel tempering strategy, a delayed rejection updating scheme and hybridizes the standard Metropolis–Hasting algorithm with the more advanced differential evolution Markov chain method. For the lack of available field seismic data, we validate the two implemented algorithms by inverting synthetic seismic data derived on the basis of realistic subsurface models and actual well log data. The two approaches are also benchmarked against two analytical inversion approaches that assume Gaussian-mixture-distributed elastic parameters. The final predictions and the convergence analysis of the two implemented methods proved that our approaches retrieve reliable estimations and accurate uncertainties quantifications with a reasonable computational effort. 相似文献
9.
Contrasts in elastic parameters can be estimated directly from seismic data using offset-dependent information in the PP reflection coefficient. A linear approximation to the PP reflection coefficient including three coefficients is fitted to the data, and relative contrasts in various elastic parameters are obtained from linear combinations of the estimated coefficients. Linearized elastic parameter sections for the contrasts in P-wave impedance, P-wave velocity, density, plane-wave modulus, and the change in bulk modulus and shear modulus normalized with the plane-wave modulus are estimated. If the average P- to S-wave velocity ratio is known, linearized parameter sections including the contrast in the average P- to S-wave velocity ratio and a fluid factor section can be computed. Applied to synthetic data, visual comparison of the estimated and true elastic parameter sections agree qualitatively, and the results are confirmed by an analysis of the standard deviation of the estimated parameters. The parameter sections obtained by inversion of a shallow seismic anomaly in the Barents Sea are promising, but the reliability is uncertain because neither well data nor regional trends are available. 相似文献
10.
Constraining the anisotropy structure of the crust by joint inversion of seismic reflection travel times and wave polarizations 总被引：2，自引：0，他引：2
In the context of wide-angle seismic profiling, the determination of the physical properties of the Earth crust, such as the
elastic layer depth and seismic velocity, is often performed by inversion of P- and/or S-phases propagation data supplying
the geometry of the medium (reflector depths) or any other structural parameter (P- or S-wave velocity, density...). Moreover,
the inversion for velocity structure and interfaces is commonly performed using only seismic reflection travel times and/or
crustal phase amplitudes in isotropic media. But it is very important to utilize more available information to constrain the
non-uniqueness of the solution. In this paper, we present a simultaneous inversion method of seismic reflection travel times
and polarizations data of transient elastic waves in stratified media to reconstruct not only layer depth and vertical P-wave
velocity but also the anisotropy feature of the crust based on the estimation of the Thomsen’s parameters. We carry out
a checking with synthetic data, comparing the inversion results obtained by anisotropic travel-time inversion to the results
derived by joint inversion of seismic reflection travel times and polarizations data. The comparison proves that the first
procedure leads to biased anisotropic models, while the second one fits nearly the real model. This makes the joint inversion
method feasible. Finally, we investigate the geometry, P-wave velocity structure and anisotropy of the crust beneath Southeastern
China by applying the proposed inversion method to previously acquired wide-angle seismic data. In this case, the anisotropy
signature provides clear evidence that the Jiangshan-Shaoxing fault is the natural boundary between the Yangtze and Cathaysia
blocks. 相似文献
11.
Umberto Spagnolini 《Geophysical Prospecting》1994,42(3):241-259
Minimization of seismic residuals does not guarantee uniqueness of the model, and this implies ambiguities in the inversion. Amplitude vs. offset (AVO) inversion does not lead to a unique solution of single elastic interface parameters unless converted and S-wave or critical angle reflections are available. Given the ambiguity of AVO inversion, this paper discusses the interaction between AVO and velocity estimation. The number of independent parameters necessary to describe an isolated reflection with AVO behaviour and residual velocity error is determined. Statistical analysis allows the establishment of an approximate equivalence of the effects of AVO and slight velocity variations; this equivalence cannot be solved without geological a priori information (kinematic equivalence). The data are then decomposed into compound events (i.e. sequences of N interfaces that follow each other at a fixed time lag). The decomposition is obtained by extrapolating the results of the analysis from narrowband to wideband data. Compound events decomposition demonstrates that AVO inversion is ambiguous, not only in the physical parameter space (P- and S-wave velocities, and density) but also kinematically. As an example of compound event decomposition, a medium is derived. This medium is geologically implausible but is kinematically equivalent. 相似文献
12.
13.
Parameters in a stack of homogeneous anelastic layers are estimated from seismic data, using the amplitude versus offset (AVO) variations and the travel-times. The unknown parameters in each layer are the layer thickness, the P-wave velocity, the S-wave velocity, the density and the quality factor. Dynamic ray tracing is used to solve the forward problem. Multiple reflections are included, but wave-mode conversions are not considered. The S-wave velocities are estimated from the PP reflection and transmission coefficients. The inverse problem is solved using a stabilized least-squares procedure. The Gauss-Newton approximation to the Hessian matrix is used, and the derivatives of the dynamic ray-tracing equation are calculated analytically for each iteration. A conventional velocity analysis, the common mid-point (CMP) stack and a set of CMP gathers are used to identify the number of layers and to establish initial estimates for the P-wave velocities and the layer thicknesses. The inversion is carried out globally for all parameters simultaneously or by a stepwise approach where a smaller number of parameters is considered in each step. We discuss several practical problems related to inversion of real data. The performance of the algorithm is tested on one synthetic and two real data sets. For the real data inversion, we explained up to 90% of the energy in the data. However, the reliability of the parameter estimates must at this stage be considered as uncertain. 相似文献
14.
Amplitude variations with offset or incident angle (AVO/AVA) inversion are typically combined with statistical methods, such as Bayesian inference or deterministic inversion. We propose a joint elastic inversion method in the time and frequency domain based on Bayesian inversion theory to improve the resolution of the estimated P- and S-wave velocities and density. We initially construct the objective function using Bayesian inference by combining seismic data in the time and frequency domain. We use Cauchy and Gaussian probability distribution density functions to obtain the prior information for the model parameters and the likelihood function, respectively. We estimate the elastic parameters by solving the initial objective function with added model constraints to improve the inversion robustness. The results of the synthetic data suggest that the frequency spectra of the estimated parameters are wider than those obtained with conventional elastic inversion in the time domain. In addition, the proposed inversion approach offers stronger antinoising compared to the inversion approach in the frequency domain. Furthermore, results from synthetic examples with added Gaussian noise demonstrate the robustness of the proposed approach. From the real data, we infer that more model parameter details can be reproduced with the proposed joint elastic inversion. 相似文献
15.
Joint AVO inversion, wavelet estimation and noise-level estimation using a spatially coupled hierarchical Bayesian model 总被引：1，自引：0，他引：1
The main objective of the AVO inversion is to obtain posterior distributions for P-wave velocity, S-wave velocity and density from specified prior distributions, seismic data and well-log data. The inversion problem also involves estimation of a seismic wavelet and the seismic-noise level. The noise model is represented by a zero mean Gaussian distribution specified by a covariance matrix. A method for joint AVO inversion, wavelet estimation and estimation of the noise level is developed in a Bayesian framework. The stochastic model includes uncertainty of both the elastic parameters, the wavelet, and the seismic and well-log data. The posterior distribution is explored by Markov-chain Monte-Carlo simulation using the Gibbs' sampler algorithm. The inversion algorithm has been tested on a seismic line from the Heidrun Field with two wells located on the line. The use of a coloured seismic-noise model resulted in about 10% lower uncertainties for the P-wave velocity, S-wave velocity and density compared with a white-noise model. The uncertainty of the estimated wavelet is low. In the Heidrun example, the effect of including uncertainty of the wavelet and the noise level was marginal with respect to the AVO inversion results. 相似文献
16.
Imaging the PP- and PS-wave for the elastic vector wave reverse-time migration requires separating the P- and S-waves during the wave field extrapolation. The amplitude and phase of the P- and S-waves are distorted when divergence and curl operators are used to separate the P- and S-waves. We present a P- and S-wave amplitude-preserving separation algorithm for the elastic wavefield extrapolation. First, we add the P-wave pressure and P-wave vibration velocity equation to the conventional elastic wave equation to decompose the P- and S-wave vectors. Then, we synthesize the scalar P- and S-wave from the vector Pand S-wave to obtain the scalar P- and S-wave. The amplitude-preserved separated P- and S-waves are imaged based on the vector wave reverse-time migration (RTM). This method ensures that the amplitude and phase of the separated P- and S-wave remain unchanged compared with the divergence and curl operators. In addition, after decomposition, the P-wave pressure and vibration velocity can be used to suppress the interlayer reflection noise and to correct the S-wave polarity. This improves the image quality of P- and S-wave in multicomponent seismic data and the true-amplitude elastic reverse time migration used in prestack inversion. 相似文献
17.
Bayesian Markov chain Monte Carlo inversion for anisotropy of PP- and PS-wave in weakly anisotropic and heterogeneous media 
下载免费PDF全文
下载免费PDF全文 A single set of vertically aligned cracks embedded in a purely isotropic background may be considered as a long-wavelength effective transversely isotropy (HTI) medium with a horizontal symmetry axis. The crack-induced HTI anisotropy can be characterized by the weakly anisotropic parameters introduced by Thomsen. The seismic scattering theory can be utilized for the inversion for the anisotropic parameters in weakly anisotropic and heterogeneous HTI media. Based on the seismic scattering theory, we first derived the linearized PP- and PS-wave reflection coefficients in terms of P- and S-wave impedances, density as well as three anisotropic parameters in HTI media. Then, we proposed a novel Bayesian Markov chain Monte Carlo inversion method of PP- and PS-wave for six elastic and anisotropic parameters directly. Tests on synthetic azimuthal seismic data contaminated by random errors demonstrated that this method appears more accurate, anti-noise and stable owing to the usage of the constrained PS-wave compared with the standards inversion scheme taking only the PP-wave into account. 相似文献
18.
孔隙介质的黏弹性、孔隙流体的Biot流动和喷射流动是影响波传播的重要物理机制.本文分别基于弹性和黏弹性BISQ模型,利用自适应杂交遗传算法研究了多种物理机制耦合作用条件下储层介质参数反演.为了测试自适应杂交遗传算法的有效性,本文分别利用自适应杂交遗传算法和传统实数编码遗传算法对含有不同噪声的理论合成数据进行了反演试算.对比理论合成数据反演结果可知,自适应杂交遗传算法具有抗干扰能力强且收敛速度快的特点,是一种有效的储层介质参数反演方法.同时本文也利用不同频率尺度和不同温度条件下的P波和S波实测数据进行了联合反演.对比研究表明,黏弹性BISQ模型能够很好地解释不同频率尺度的波频散特征,不仅能够很好地预测P波速度,而且也能够很好地预测S波速度,从而证明了黏弹性BISQ模型能够准确地描述低频条件下的波频散. 相似文献
19.
AVO反演可以获得地层岩性和流体信息,而叠前反演问题都是高维的和非适定的,因此获得可靠稳定的解对叠前反演至关重要. 本文给出了一种基于贝叶斯理论的纵波和转换波联合反演密度比和模量比的方法. 鉴于剪切模量比、体积模量比可以更好地指示油气,基于岩石物理中速度比与模量比之间的关系,将此关系式代入Zoeppritz方程的近似形式Aki-Richards公式中,得到与模量比有关的反射系数近似公式. 联合纵波和转换波,利用最小二乘准则构建目标函数,最终反演出密度比、剪切模量比、体积模量比三个参数. 在反演过程中引入贝叶斯理论,假定先验信息服从高斯分布,待求参数服从改进的Cauchy分布,并去除待求参数之间的相关性. 利用模型数据和实际数据对本文方法进行测试,并与常规的单独利用纵波数据来反演方法进行比较,结果表明联合反演稳定性更好、精度更高、抗噪音能力更强,验证了本文方法的可行性和有效性. 相似文献
20.