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反射系数反演是联结地下储层和地震数据的桥梁,奇偶分解算法的出现使得子波间调谐效应减弱,这使得基于压缩感知的谱反演得到进一步应用.由于谱反演算法的不稳定性,所得到的反射系数横向连续性较差.因此,提出叠后地震数据倾角约束的多道谱反演算法,算法认为地震数据沿倾角方向具有一定连续性,在常规单道谱反演的基础上,推导了多道谱反演算法,基于局部倾角增加沿地层倾向的平滑约束,解决大角度地层反演横向连续性差的问题.算法继承了谱反演的高分辨率特性,并且有效增强了横向连续性,适用于地震数据的反射系数反演.模型和实际数据测试证明了倾角约束的多道谱反演算法得到的反演结果不仅能识别薄层,还能保持原始地层模型的横向连续性特征,并且具有一定的抗噪性,为地震地层学精细解释提供依据. 相似文献
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地震资料反演的目的是估计地层的物理参数(密度、弹性和粘弹性参数)的实际值.本文中将最佳估计值定义为一种参数集,由该参数集可以算出与地震实际资料最佳拟合的合成地震记录.本文提出一种新的地层弹性参数反演方法,主要适用于各向异性介质(横向各向同性介质)中地层弹性参数的反演.本方法不同于过去传统的反演方法,它是一种完全意义上的全波波动方程反演,利用地震勘探中的多波多分量记录(PP反射波记录和PSV转换波记录)联合进行地层弹性参数犆11和犆33反演,用以判断地层的属性. 相似文献
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WTW(Wave equation traveltime+Waveform inversion)反演是基于波动方程的走时反演(WT反演)和波形反演的联合反演方法.WT反演利用波动方程计算走时和走时关于速度的导数,和传统以射线为基础的走时反演相比,具有不必射线追踪、不必拾取初至、不必高频假设以及初始模型和实际模型差别较大时也能较好收敛等优点,但WT反演与波形反演相比其结果分辨率低.与之互补的是,波形反演的反演结果分辨率高,但是当所给初始模型和实际模型相差太大时,波形反演迭代算法容易陷入局部极小点.可见结合两种方法的WTW反演是一种比较好的联合反演方法.常规WTW迭代算法是首先以WT反演为主反演得到地质模型的整体特征,然后再以波形反演为主反演模型细节,该算法耗时和占用计算机存储空间接近WT反演或波形反演的两倍.为了节省运算耗时和计算机存储空间,往往采取首先单独利用WT反演然后再单独利用波形反演的算法.这样做的缺点是不能紧密结合两种反演方法,使得它们的优缺点在每一次迭代中无法得到互补,从而影响了最终的反演结果.针对以上事实,本文提出一种新的方法实现WTW,使得WTW运算速度和存储空间在任何情况下等同于WT反演或波形反演.模型计算表明新的算法具有更好的收敛性. 相似文献
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反演本质上具有不适定性,在反演过程中采用一定的策略很有必要.本文采用反射率法正演、共轭梯度法反演的正反演体系,从不同频带数据的最佳收敛步长、目标函数的组成等方面对反演的影响进行了探讨.在此基础上采用分频反演、分层反演及变权重目标函数的策略,利用海上测井弹性参数模型对地震叠前波形数据进行了弹性参数反演试验.通过对反演结果的分析指出对反演的中间结果进行质量评估和质量控制的必要性. 相似文献
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开发导致的时移地震差异代表了油藏的岩石物理性质变化,本文从差异波形角度出发,明确了声波阻抗界面的反射系数与油层声波阻抗变化之间的函数关系,进而分析薄油层时移地震差异波形特征.通过分析得出,开发前后油层阻抗变化越大,时移地震的差异振幅幅度越大;薄油层的差异波形特征仅与油层的声波阻抗变化有关,油层声波阻抗增大导致与地震子波微分形式相同的差异波形,油层声波阻抗减小产生的差异波形与180°相位的地震子波微分形式相同;油层声波阻抗变化方向导致差异波形振幅幅度变化的快慢. 相似文献
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Acoustic impedance is one of the best attributes for seismic interpretation and reservoir characterisation. We present an approach for estimating acoustic impedance accurately from a band‐limited and noisy seismic data. The approach is composed of two stages: inverting for reflectivity from seismic data and then estimating impedance from the reflectivity inverted in the first stage. For the first stage, we achieve a two‐step spectral inversion that locates the positions of reflection coefficients in the first step and determines the amplitudes of the reflection coefficients in the second step under the constraints of the positions located in the first step. For the second stage, we construct an iterative impedance estimation algorithm based on reflectivity. In each iteration, the iterative impedance estimation algorithm estimates the absolute acoustic impedance based on an initial acoustic impedance model that is given by summing the high‐frequency component of acoustic impedance estimated at the last iteration and a low‐frequency component determined in advance using other data. The known low‐frequency component is used to restrict the acoustic impedance variation tendency in each iteration. Examples using one‐ and two‐dimensional synthetic and field seismic data show that the approach is flexible and superior to the conventional spectral inversion and recursive inversion methods for generating more accurate acoustic impedance models. 相似文献
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套管井声全渡中的地层波可以检测固井第二界面的水泥胶结质量状况.地层波不仅受地层衰减、套管波干扰等因素影响,更主要受第二界面两侧的声阻抗差值的影响.为此,基于固体介质的声势函数和界面的边界条件,推导了固-固界面纵横波的反射系数和透射系数,以及第一临界角入射情况下反射系数和透射系数的近似公式,并且分析了透射系数与声阻抗之间的关系.数值计算结果发现,地层波幅度随第二界面两侧声阻抗差增大而减小,且这种关系是非线性的.基于临界入射的透射系数,对经过衰减校正和干扰校正的地层波进行声阻抗校正,消除地层声阻抗对地层波幅度影响.使用地层波幅度评价第二界面的水泥胶结状况,并在实际资料处理中见到了好的效果. 相似文献
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The application of elastic impedance inversion in reservoir prediction at the Jinan area of Tarim Oilfield 总被引:1,自引:0,他引:1
The Triassic reservoir in the Jinan area of Tarim Oilfield consists largely of interbedded sand and shale. Because of the large overlap between sandstone and shale impedance, it is difficult to distinguish sandstone from shale by acoustic impedance alone. Compared to acoustic impedance, elastic impedance contains more lithologic and physical information of the reservoir. Based on meticulous well-tie calibration, elastic impedance data volumes for 10°, 20°, and 30° emergence angles are obtained using pre-stack elastic impedance inversion. A non-linear statistical relationship between elastic impedance and shale content is set up by a PNN neural network. The non-linear mapping relationship is used to predict the reservoir shale content from elastic impedance, which will depict and predict the reservoir oil-bearing sands. 相似文献
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针对利用地震道进行相对波阻抗反演中遇到的横向连续性难以保持、初始子波容错度差以及随机噪声干扰影响反演结果等问题,提出了一种基于矩阵Toeplitz稀疏分解的相对波阻抗反演方法.该方法将地震数据剖面的Toeplitz稀疏分解问题分解为两个子反演问题,其一以Toeplitz子波矩阵元素为待反演的参数,用Fused Lasso方法求解,可保证子波具有紧支集且是光滑的;其二以稀疏反射系数矩阵元素为待反演参数,用基于回溯的快速萎缩阈值迭代算法求解,大大降低了目标函数中参数选择的难度.通过交替迭代求解上述两个子反演问题可将地震数据剖面因式分解为一个Toeplitz子波矩阵和一个稀疏反射系数矩阵;然后由反射系数矩阵递推反演可以得到高分辨率的相对波阻抗剖面;利用测井资料加入低频分量后,也可得到高分辨率的绝对波阻抗剖面.Marmousi2模型生成的合成记录算例和实际地震资料算例均表明:本文方法可以从带限地震数据中有效地反演相对波阻抗,反演结果分辨率高并且能够很好地保持地震数据的横向连续性;即使在初始估计子波存在误差和地震数据被随机噪声污染的情况下也能取得较好的效果. 相似文献
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针对套管井反射式超声波水泥固井质量检测问题,本文利用超声反射波频谱中套管共振透射窗内的复合反射系数,提出了定量反演套管-地层环空间内介质的波阻抗的方法. 利用复合反射系数中多个频率点的相移反正切函数主值,给出了波阻抗的计算公式,并把套管-地层环空间介质中波的相移的整、实特性作为波阻抗反演收敛的判据. 针对井下实际测井环境中超声换能器性能受温度和压力等的影响而发生变化,导致的声源波形(子波)和复合反射系数不确定的困难,提出了用井下原地(in situ)实测波形定量估计声源波形和复合反射系数的方法. 通过对合成数据的处理,分别考察了已知介质的声学和几何参数存在的偏差对套管-地层环空间内介质的波阻抗反演结果的影响. 本文对多组模型井检验数据进行了目的层介质的波阻抗反演与成像,成像结果与真实情况吻合,验证了反演方法的有效性. 最后对现场实测资料进行了套管-地层环空间内介质的波阻抗定量反演与成像. 相似文献
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Frequency‐domain waveform modelling and inversion for coupled media using a symmetric impedance matrix
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To simulate the seismic signals that are obtained in a marine environment, a coupled system of both acoustic and elastic wave equations is solved. The acoustic wave equation for the fluid region simulates the pressure field while minimizing the number of degrees of freedom of the impedance matrix, and the elastic wave equation for the solid region simulates several elastic events, such as shear waves and surface waves. Moreover, by combining this coupled approach with the waveform inversion technique, the elastic properties of the earth can be inverted using the pressure data obtained from the acoustic region. However, in contrast to the pure acoustic and elastic cases, the complex impedance matrix for the coupled media does not have a symmetric form because of the boundary (continuity) condition at the interface between the acoustic and elastic elements. In this study, we propose a manipulation scheme that makes the complex impedance matrix for acoustic–elastic coupled media to take a symmetric form. Using the proposed symmetric matrix, forward and backward wavefields are identical to those generated by the conventional approach; thus, we do not lose any accuracy in the waveform inversion results. However, to solve the modified symmetric matrix, LDLT factorization is used instead of LU factorization for a matrix of the same size; this method can mitigate issues related to severe memory insufficiency and long computation times, particularly for large‐scale problems. 相似文献
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Ultrasonic cement bond logging is a widely used method for evaluating cementing quality. Conventional ultrasonic cement bond logging uses vertical incidence and cannot accurately evaluate lightweight cement bonding. Oblique incidence is a new technology for evaluating cement quality with improved accuracy for lightweight cements. In this study, we simulated models of acoustic impedance of cement and cementing quality using ultrasonic oblique incidence, and we obtained the relation between cementing quality, acoustic impedance of cement, and the acoustic attenuation coefficient of the A0-mode and S0-mode Lamb waves. Then, we simulated models of different cement thickness and we obtained the relation between cement thickness and the time difference of the arrival between the A0 and A0′ modes. 相似文献
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O. N. Savina P. A. Bespalov V. O. Rapoport N. A. Ryzhov 《Geomagnetism and Aeronomy》2006,46(2):247-253
The nonlinear equation of the first order of the Riccati type has been obtained for the wave impedance of acoustic gravity waves in the nonisothermal atmosphere. The vertically nonuniform horizontal wind and the effect of viscosity on the horizontal components of the velocity field have been taken into account in the calculations. The boundary-value problem for the Riccati equation is defined by the boundary emission condition at high altitudes. Upon finding the wave impedance along with the generalized polarization relationship, all remaining disturbances of the atmospheric parameters related to acoustic gravity waves are found with the help of a simple integration. The results of using a developed formalism are illustrated by the numerical computation of acoustic gravity wave fields in the atmosphere with real vertical profiles of temperature and horizontal field velocity. 相似文献