利用多波地震与测井数据联合反演预测煤岩的坚固性

基于煤岩的坚固性、变形模量以及纵、横波速度之间的岩石力学规律,提出用多波地震与测井数据的联合反演定量化预测煤岩的坚固性.根据煤田三维三分量地震采集的特点,建立了PP波与PS波平均入射角部分叠加道集的井约束反演流程;利用煤岩的坚固性系数与变形模量之间的换算关系对目标煤层的坚固性系数空间变化规律进行预测,并划分可能发生煤与...     

基于角弹性参数的多波地震储层预测方法

弹性参数作为反映岩石弹性性质的参数,在储层预测中具有重要作用.常规弹性参数的构建主要基于PP波地震信息.PP波与PS波地震振幅因其携带的信息不同,对岩性与流体的敏感性也不同.本文提出联合利用PP波与PS波弹性阻抗以及角度信息构建角弹性参数来预测有利储层.首先,对常规PS波弹性阻抗方程进行重新推导,使得PS波弹性阻抗取值的数量级不随角度变化且能够与PP波弹性阻抗具备形式上的匹配;其次,根据常规弹性参数构建公式,采用PP波弹性阻抗、PS波弹性阻抗替代纵波阻抗、横波阻抗,提出角弹性参数的概念及构建公式,从而将角度信息引入到弹性参数的构建中;最后,在PP波与PS波弹性阻抗反演的基础上构建得到对储层敏感性较强的角弹性参数,利用角弹性参数的取值特征预测有利储层.模型与实际资料测试均表明角弹性参数具备较高的储层敏感性.     

基于改进的贝叶斯推断和最小二乘支持向量机的非线性多波联合AVO反演（英文）

多波地震资料采集和处理技术的发展促进了联合PP波和PS波数据的多波联合AVO反演的应用,常规多波联合反演是线性的,通常基于Zoeppritz方程近似式进行多次迭代,导致其在远炮检距情况下求解得到的纵、横波速度和密度等参数精度不高。多波联合反演存在非线性问题。为此,本文提出了一种基于精确Zoeppritz方程的非线性反演方法。该方法结合改进的贝叶斯推断和最小二乘支持向量机方法来求解非线性反演问题。首先,采用粒子群算法来优化贝叶斯推断的参数初始值。改进的贝叶斯推断是通过最大化超参数的后验概率来获得最小二乘支持向量机的最优参数,提高了最小二乘支持向量机的学习和泛化能力。然后,利用此最优参数建立PP波、PS波反射振幅与弹性参数之间的最优非线性最小二乘支持向量机模型,从而提高了多波联合反演的精度。该方法只需训练一次模型,就可以解决多波联合反演的非线性问题。模型测试表明,利用该方法反演出的弹性参数精度要高于仅用PP波进行贝叶斯线性近似式反演得到的结果。此外加噪模型数据的反演结果表明,该方法具有较好的抗噪性。实际多波资料的应用进一步验证了方法的可行性及其相对于PP波贝叶斯线性近似式反演的优势。     

TTI介质各向异性参数多波反演与PS波AVO分析

把遗传算法引入到了TTI介质AVO信息反演各向异性参数的过程中,依据TTI介质PP波、PS波反射系数公式,建立Thomsen参数和TTI介质对称轴倾角、方位角的目标函数,分别通过PP波和PS波的反射系数反演出了各向异性参数和对称轴倾角、方位角等信息.文中对反演结果的精确度和稳定性进行了分析,发现PS波的反演结果优于PP波反演结果;对称轴倾角的反演准确性明显优于对称轴方位角.本文通过模型正演合理解释了这一现象的原因.最后,本文通过对PS波AVO梯度的研究,提出了利用PS波振幅定性分析TTI介质对称轴倾角的方法.     

弹性矢量波成像域联合层析反演

在地震弹性矢量波场框架下,推导了多波联合层析速度反演方程以及走时残差与角道集剩余曲率的转换关系式,提出了一种利用成像域角道集更新P波、S波速度的走时层析反演方法.其实现过程可以概括为:将弹性波多分量数据作为输入,基于高斯束实现矢量波场成像并提取角道集,利用层析反演方程求解慢度更新量,最终获得多波联合反演结果.模型试算和实际资料处理验证了该方法的反演效果,能够为弹性矢量波联合深度偏移提供高质量的叠前速度场.     

基于Russell近似的纵横波联合反演方法研究

PP波和PS波联合反演方法作为有效的地震技术,比单纯纵波反演精度要高,能够提高地震储层识别的精度.以Russell近似理论为基础,推导了新的转换波AVO近似公式,双层模型界面的反射特征数值模拟显示,新公式具有较高的近似精度,且具备直接反演流体因子f、剪切模量μ和密度ρ等参数的优势,有效避免间接反演带来的误差.结合纵横波联合反演理论,提出了基于贝叶斯理论的新型联合反演算法.在实际应用中,对纵波和转换波角道集进行同相轴匹配处理,综合利用纵波和转换波资料携带的信息,实现基于Russell近似的多波联合反演.模型数据和实际资料测试结果表明,反演结果与真实值或测井结果匹配度较高,证实该方法真实有效.     

基于矢量波场逆时偏移的保幅角道集提取方法（英文）

将偏移后的炮域偏移距道集转换为角度域共成像道集(ADCIGs)可为偏移速度分析(MVA)和叠前反演提供输入道集,并且ADCIGs是理论上没有假象的叠前反演道集,也是目前公认的精度最高的叠前反演道集。本文研究了基于矢量波场逆时偏移的弹性波保幅ADCIGs的提取方法,以保幅弹性波逆时偏移方程为基础,其核心是求取不同震源位置的纵、横波场在地下各成像点的入射角,对于转换波勘探,二者共享一个入射角,即震源纵波入射角。根据几何关系,震源纵波波场的传播角、构造的局部地层倾角之差为震源纵波入射角,震源纵波波场的传播角利用解耦后纵波场的极化向量得到,构造的局部地层倾角利用偏移叠加剖面的复波数得到。对纵、横波的共炮点偏移道集按入射角重新排列即可得到各自的ADCIGs。文中利用水平层状介质模型、倾斜层状介质模型、Marmousi-Ⅱ弹性波部分模型和实测资料验证了算法的有效性,计算结果表明,本文方法计算的纵、横波角度具有较高的精度,提取的角道集具有较好的振幅保真性,能够为MVA和叠前反演提供可靠的输入道集。     

基于贝叶斯原理的PP波和PS波AVO联合反演方法研究(英文)

基于Aki-Richards公式和贝叶斯原理,本文发展了利用叠前PP波和PS波资料联合反演P波速度比、S波速度比和密度比的方法。该方法假设参数之间满足正态分布,引入参数协方差矩阵来描述反演参数之间的相关性以提高反演过程的稳定性,并同时使反演的参数序列服从Cauchy分布,引入矩阵Q来描述参数序列的稀疏性以提高反演结果的分辨率。采用本文提出的方法对模型数据和实际多波资料进行反演,结果表明:本文方法正确有效;与传统的单一PP波反演相比,PP波和PS波AVO联合反演具有稳定性更好和反演精度更高等优点。     

Kirchhoff叠前时间偏移角度道集

提出三维Kirchhoff叠前时间偏移角度域共像点道集的改进算法,克服传统角度求取算法局限,可计算相对倾斜地层法线入射角;与Kirchhoff直射线叠前时间偏移求角度算法相比,本文方法考虑射线弯曲效应,包含层速度,角度范围加大,更接近真实入射角;计算走时采取弯曲射线或者适应线性横向变速介质的非对称走时等算法,角度道集在大角度处得到拉平;采用相对保幅的权因子以及覆盖次数校正技术,有利于叠前AVA反演.模型测试结果表明：叠前时间偏移角度道集,相对CMP、CRP所转化角度道集,更准确反应AVA效应;实际三维数据测试表明本文方法可以提供品质优良的角度道集,适用于AVA分析、反演,提高叠前反演分辨率.     

基于精确Zoeppritz方程的非线性AVO三参数反演

常规AVO三参数反演通常存在密度反演不准确的问题,而密度参数对常规油气藏中的流体识别、流体饱和度计算、孔隙度计算以及非常规油气藏中TOC含量计算、裂缝预测等都至关重要,因此对于研究如何利用大偏移距振幅信息和富含密度信息的PS波地震资料来提高密度反演结果的稳定性和精度显得尤为重要.研究基于贝叶斯反演理论框架,引入三变量Cauchy分布先验约束,利用精确Zoeppritz方程构建了AVO三参数联合反演的目标函数,对目标函数进行Taylor二阶非线性简化,得到模型参数的迭代更新公式,实现了大偏移距地震振幅信息的利用和PP波、PS波联合反演.合成数据和实际地震数据的方法测试结果表明,新方法不仅可以直接反演纵波速度、横波速度和密度,而且还具有很高的精度,尤其是密度反演结果.基于合成数据的PP波、PS波单独反演结果与PP波和PS波联合反演结果对比显示,联合反演稳定性更好,精度更高,抗噪能力更强,验证了该方法的可行性和有效性.与基于Aki-Richards近似公式的反演结果对比表明,该反演方法具有更高的反演精度和更好的抗噪性.     

Multiwave velocity analysis based on Gaussian beam prestack depth migration

Prestack depth migration of multicomponent seismic data improves the imaging accuracy of subsurface complex geological structures. An accurate velocity field is critical to accurate imaging. Gaussian beam migration was used to perform multicomponent migration velocity analysis of PP- and PS-waves. First, PP- and PS-wave Gaussian beam prestack depth migration algorithms that operate on common-offset gathers are presented to extract offset-domain common-image gathers of PP- and PS-waves. Second, based on the residual moveout equation, the migration velocity fields of P- and S-waves are updated. Depth matching is used to ensure that the depth of the target layers in the PP- and PS-wave migration profiles are consistent, and high-precision P- and S-wave velocities are obtained. Finally, synthetic and field seismic data suggest that the method can be used effectively in multiwave migration velocity analysis.     

Separation of PP- and PS-wave reflected seismic data using two-dimensional finite offset common-reflection-surface traveltime approximation

Recently, the interest in PS-converted waves has increased for several applications, such as sub-basalt layer imaging, impedance estimates and amplitude-versus-offset analysis. In this study, we consider the problem of separation of PP- and PS-waves from pre-stacked multicomponent seismic data in two-dimensional isotropic medium. We aim to demonstrate that the finite-offset common-reflection-surface traveltime approximation is a good alternative for separating PP- and PS-converted waves in common-offset and common shot configurations by considering a two-dimensional isotropic medium. The five parameters of the finite-offset common-reflection-surface are firstly estimated through the inversion methodology called very fast simulated annealing, which estimates all parameters simultaneously. Next, the emergence angle, one of the inverted parameters, is used to build an analytical separation function of PP and PS reflection separation based on the wave polarization equations. Once the PP- and PS-converted waves were separated, the sections are stacked to increase the signal-to-noise ratio using the special curves derived from finite-offset common-reflection-surface approximation. We applied this methodology to a synthetic dataset from simple-layered to complex-structured media. The numerical results showed that the inverted parameters of the finite offset common-reflection-surface and the separation function yield good results for separating PP- and PS-converted waves in noisy common-offset and common shot gathers.     

A method of directly extracting multiwave angle-domain common-image gathers

Angle-domain common-image gathers (ADCIGs) can provide an effective way for migration velocity analysis and amplitude versus angle analysis in oil–gas seismic exploration. On the basis of multi-component Gaussian beam prestack depth migration (GB-PSDM), an alternative method of directly extracting multiwave ADCIGs is presented in this paper. We first introduce multi-component GB-PSDM, where a wavefield separation is proceeded to obtain the separated PP- and PS-wave seismic records before migration imaging for multiwave seismic data. Then, the principle of extracting PP- and PS-ADCIGs using GB-PSDM is presented. The propagation angle can be obtained using the real-value travel time of Gaussian beam in the course of GB-PSDM, which can be used to calculate the incidence and reflection angles. Two kinds of ADCIGs can be extracted for the PS-wave, one of which is P-wave incidence ADCIGs and the other one is S-wave reflection ADCIGs. In this paper, we use the incident angle to plot the ADCIGs for both PP- and PS-waves. Finally, tests of synthetic examples show that the method introduced here is accurate and effective.     

Bayesian Markov chain Monte Carlo inversion for anisotropy of PP- and PS-wave in weakly anisotropic and heterogeneous media

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.     

基于Zoeppritz偏导方程精确解的地层密度多角度反演

基于Zoeppritz方程对介质密度偏导数所建立的偏导方程的精确解,构造了多角度反演地层介质密度的反演方程,在偏导数求解过程中考虑了介质密度对波速度的影响因素,并由此实现了利用反射系数梯度精确解计算地层密度的多角度联合反演.通过数值算例考察了计算方法,结果显示:反演方法对层状地层模型不论反射波是否存在相干现象均获得了较好的反演结果,反演迭代10次后计算结果的最大相对误差能够收敛到1%之内;随着反演角度的增加地层介质密度反演的精度逐步提高,反演具有自动校正能力,有快的计算速度.本方法克服了传统AVO(Amplitude Versus Offset)基于Zoeppritz方程近似所遇到的困难,不受反演角度大小及反射界面对波反射强弱的限制,为地层介质密度的多角度包括大角度反演提供了一种新的快速有效的计算方法.     

Generalized linear joint PP–PS inversion based on two constraints

Conventional joint PP—PS inversion is based on approximations of the Zoeppritz equations and assumes constant VP/VS; therefore, the inversion precision and stability cannot satisfy current exploration requirements. We propose a joint PP—PS inversion method based on the exact Zoeppritz equations that combines Bayesian statistics and generalized linear inversion. A forward model based on the exact Zoeppritz equations is built to minimize the error of the approximations in the large-angle data, the prior distribution of the model parameters is added as a regularization item to decrease the ill-posed nature of the inversion, low-frequency constraints are introduced to stabilize the low-frequency data and improve robustness, and a fast algorithm is used to solve the objective function while minimizing the computational load. The proposed method has superior antinoising properties and well reproduces real data.     

An Accurate Method of Computing the Gradient of Seismic Wave Reflection Coefficients (SWRCs) for the Inversion of Stratum Parameters

The optimization inversion method based on derivatives is an important inversion technique in seismic data processing, where the key problem is how to compute the Jacobian matrix. The computational precision of the Jacobian matrix directly influences the success of the optimization inversion method. Currently, most of the AVO (amplitude versus offset) inversions are based on approximate expressions for the Zoeppritz equations to obtain the derivatives of the seismic wave reflection coefficients (SWRCs) with respect to the stratum parameters. As a result, the computational precision and range of applications of these AVO inversions are restricted undesirably. In order to improve the computational precision and to extend the range of applications of AVO inversions, the partial derivative equations of the Zoeppritz equations are established, with respect to the ratios of wave velocities and medium densities. By solving the partial derivative equations of the Zoeppritz equations accurately, we obtained the partial derivative of SWRCs with respect to the ratios of seismic wave velocities and medium densities. With the help of the chain rule for derivatives, the gradient of the SWRCs can be accurately computed. To better understand the behavior of the gradient of the SWRCs, we plotted the partial derivative curves of the SWRCs, analyzed the characteristics of these curves, and gained some new insight into the derivatives. Because only a linear system of equations is solved in our method without adding any new restrictions, the new computational method has both high precision and a quick running speed; it is not only suitable for small incident angles and weak reflection seismic waves but also for large incident angles and strong reflection seismic waves. With the theoretical foundations established in the article, we can further study inversion problems for layered stratum structures and we can further improve the computational speed and precision of the inversions.     

三维倾斜界面PS转换波CMP道集时距及参数估计

在PS转换波资料处理过程中,往往需要联合P波资料提供相应的模型.在实际应用中存在P波和PS转换波层位对比困难.本文仅利用PS转换波数据,通过三维倾斜界面PS转换波CMP道集精确时距关系推导了近似时距解析表达式;分析了PS波的精确与近似时距关系随测线方位、界面倾角与倾向的变化规律及其拟合误差;并讨论了近似时距关系的三个时距参数随方位的变化特征;理论上给出描述时距的三维倾斜界面倾角、倾向、深度、纵波速度和横波速度这5个独立参数的估计方法,并通过理论模拟数据证明了该方法的可行性.