Impedance inversion of pre-stack seismic data in the depth domain

The extensive application of pre-stack depth migration has produced huge volumes of seismic data,which allows for the possibility of developing seismic inversions of reservoir properties from seismic data in the depth domain.It is difficult to estimate seismic wavelets directly from seismic data due to the nonstationarity of the data in the depth domain.We conduct a velocity transformation of seismic data to make the seismic data stationary and then apply the ridge regression method to estimate a constant seismic wavelet.The estimated constant seismic wavelet is constructed as a set of space-variant seismic wavelets dominated by velocities at different spatial locations.Incorporating the weighted superposition principle,a synthetic seismogram is generated by directly employing the space-variant seismic wavelets in the depth domain.An inversion workflow based on the model-driven method is developed in the depth domain by incorporating the nonlinear conjugate gradient algorithm,which avoids additional data conversions between the time and depth domains.The impedance inversions of the synthetic and field seismic data in the depth domain show good results,which demonstrates that seismic inversion in the depth domain is feasible.The approach provides an alternative for forward numerical analyses and elastic property inversions of depth-domain seismic data.It is advantageous for further studies concerning the stability,accuracy,and efficiency of seismic inversions in the depth domain.

A Method of Improving Seismic Data Resolution：Comprehensive Inversion of Well logging and Seismic Data

Comprehensive inversion of logging and seismic data presented in this paper is a method to improve seismic data resolution. It involves using ample high-frequency information and complete low-frequency information of known logging to make up for the lack of limited bandwidth of practical seismic recording, obtaining an approximate reflection coefficient sequence (or wave impedance) of high resolution by iterative inversion and providing more reliable seismic evidence for further lithologic interpretation and lateral tracking, correlation and prediction of thin reservoir. The comprehensive inversion can be realized in the following steps: (1) to establish an initial model of higher resolution; (2) to obtain wavelets, and (3) to constrain iterative inversion. The key to this inversion lies in building an initial model. It is assumed from our experience that when the initial model is properly given, iterative inversion can be quickly converged to the ideal result.

Pre-stack seismic density inversion in marine shale reservoirs in the southern Jiaoshiba area, Sichuan Basin, China

For a typical marine shale reservoir in the Jiaoshiba area, Sichuan Basin of China, P-impedance is sensitive for identifying lithology but not suitable for indicating good shale reservoirs. In comparison, density is an important quantity, which is sensitive for identifying the organic-rich mud shale from non-organic-rich mud shale. Due to the poor data quality and incidence angle range, density cannot be easily inverted by directly solving the ill-posed pre-stack seismic inversion in this area. Meanwhile, the traditional density regularizations implemented by directly using the more robust P-impedance inversion tend to be inaccurate for recovering density for this shale reservoir. In this paper, we combine the P-impedance and the minus uranium to construct the pseudo-P-impedance（PIp） at well locations. The PIp is observed to be sensitive for identifying organic-rich mud shale and has a good correlation with density in this area. We employ the PIp–density relation into the pre-stack inversion framework to estimate density. Three types of regularization are tested on both numerical and field data： These are no regularization, traditional regularization and the proposed approach. It is observed that the proposed method is better for recovering the density of organic-rich mud shale in the Jiaoshiba area.

Application of Seismic Inversion Using Logging Data as Constraints in Coalfield

Seismic inversion and basic theory are briefly presented and the main idea of this method is introduced. Both non-linear wave equation inversion technique and Complete Utilization of Samples Information (CUSI) neural network analysis are used in lithological interpretation in Jibei coal field. The prediction results indicate that this method can provide reliable data for thin coal exploitation and promising area evaluation.

Application of Reservoir Seismic Inversion to the Damintun Sag in the Liaohe Oilfield

According to the special geologic conditions of the Damintun （大民屯） sag in the Liaohe （辽河） basin, with a complex structure and rapid lateral change of thin interbeds, the technique of logging-constraint seismic inversion based on prestack high-resolution seismic data was used in the description of oil-gas reservoirs. Reservoir seismic inversion can effectively identify underground complex geologic structures and seismic anomalous reflection volumes and quantitatively predict the distribution of sandstones in space and their variant law in combination with lithologic interpretation. This work studies the wave impedance inversion of high-resolution prestack seismic data, and logging multi-attribute data inversion, and applies these methods to the Damintun sag. As a result, the vertical resolution of reservoir prediction is raised, ability of identifying thin-interbed sand bodies is enhanced, reliability of reservoir prediction is improved, and favorable lithologic traps of this area are further confirmed. These effects are of significance in the exploration of hidden hydrocarbons in this oilfield.

A THEORY FOR WAVE EQUATION INVERSE PROBLEM:THE UNION METHOD FOR SCATTERED WAVEEXTRAPOLATION AND VELOCITY IMAGING

A new theory for inverse problem of wave equation, that is, the union method for scattered wave extrapolation and velocity imaging, is proposed in this paper. This method is very different from the classical wave extrapolation for migration, because we relate directly the scattered wave extrapolation to velocity inversion. And also this method is different from any linearized inverse method of wave equation, because we needn′t use linearized approximation. Because of this, the method can be applied to strong scattering case effectively (i.e. the value of scattered wave is not small, which can not be neglected). This method, of course, is different from nonlinearized optimum inverse method, because in this paper, the nonlinear inverse problem is turned into two steps inverse problem, i.e. scattered wave extrapolated and velocity imaging, which can be solved easily. Hence, the problem how to get the global optimum solution by using the nonlinearized optimum inverse method doesn′t bother us by using the method in this paper.

基于多层残差网络的地震提频处理在薄储集层识别中的应用

基于多层残差网络的地震提频处理方法,通过智能化网络将测井高频信息与地震数据相结合,能有效提升纵向分辨率,保持横向连续可追踪,利于薄储集层识别。针对AMH地区常规处理的地震数据仅能识别厚度大于30 m的碳酸盐岩层,无法有效识别厚度较小的薄储集层的问题,提出基于多层残差网络的地震提频处理方法,以井旁地震振幅作为训练数据,测井相对波阻抗作为训练标签,利用深度学习网络多层残差网络开展训练,获取相对波阻抗曲线的预测模型;通过将地震数据作为输入,利用深度网络训练模型计算得到相对波阻抗数据体,进而得到提频后的地震数据体相对应的反射系数体。通过对靶区地质情况的分析认识,对宽频子波进行标定后提取合适的宽频子波,与反射系数体进行褶积,得到提频后的地震数据体;利用提频后的地震数据体开展储集层反演,反演结果纵向具有较高分辨率,与主要目的层能够较好匹配,横向可以进行识别和追踪,利用高分辨地震数据反演结果实现AMH地区的薄储集层识别。结果表明,通过基于多层残差网络的地震提频处理及相应的高分辨模型反演,在AMH地区能够识别厚度大于10 m的薄储集层,较好地解决由于地震分辨率低无法识别薄储集层的问题,有效提高了薄储集层预测的精度,对同类型薄储集层识别具有借鉴意义。

应用L_(p)拟范数稀疏约束的纵横波速比直接反演

纵横波速比(vP/vS)是识别气藏、描述储层特征和判别岩性的重要解释工具。目前主要是通过反射系数近似方程反演得到纵、横波速度,再进一步计算纵横波速比,但是这种间接计算方法会产生累积误差。为了直接从叠前地震数据反演纵横波速比,文中提出了一种新的广义弹性阻抗方程,再进一步推导出一个与纵横波速比、纵波速度、密度相关的纵波反射系数近似方程。为了得到精度较高的反演结果,基于推导出的反射系数近似方程,提出一种基于Lp拟范数稀疏约束的叠前地震反演方法,并通过交替方向乘子算法求解。将提出的直接反演方法应用于理论模型和实际数据,并与间接反演方法相对比,结果表明该直接反演方法的反演结果精度较高,对含气储层的边界刻画更清晰。

陆梁油田侏罗系油藏薄储层预测方法及应用

陆梁油田侏罗系油藏具有一定开发潜力。侏罗系西山窑组自上而下为3段,含油层为西山窑一段,据段内多个泥岩隔层分布进一步将西一段划分为2个油层组5个小层,具“一砂一藏”特点。由于5~10 m薄砂层很难直接在地震剖面上成像,为侏罗系西山窑组油藏的薄储层精准预测带来了一定困难。为了解油层及薄储层的平面及空间展布特征,本次研究基于钻井、测井、试油等资料,以三维叠后地震数据的子波主频,建立研究区地震记录波形与合成记录波形两个信号的互相关函数计算衰减系数Qf,并完成时-频衰减高精度合成记录标定。通过确定地震波阻抗识别门槛值,结合薄储层地震振幅属性数据体与岩性解释的储层特征分析资料,输出西山窑组西一段地震波阻抗反演剖面及油层厚度图。预测结果表明,开发井油层厚度为5~8 m薄砂体,与实际资料准确率达90%,为油藏开发扩边提供了理论依据。

模型反演和深度学习反演联合的地震波阻抗优化反演

基于“数据驱动和模型驱动”相结合的思想,通过模型反演结果扩展标签训练集,并在深度学习算法中加入模型反演目标函数,对损失函数进行重构,提出了一种模型反演和深度学习反演联合的地震波阻抗优化反演。采用RNN网络结构实现了一种“伪标签”下的半监督深度学习网络反演,并用网络反演结果作为初始模型参与模型反演,最终优化反演由网络反演和模型反演不断迭代优化完成。通过合成Marmousi模型和实际资料,验证了所提出的方法具有较高的反演精度和实用性。

地震横波建模技术及其在深水天然气田储层预测中的应用

深水区缺少横波资料,在叠前反演的建模环节中,一般通过线性关系或者相控将纵波模型转换为横波模型,但实现过程受人为因素影响较大,反演结果无法完整、可靠地表征地层特点和储层分布。为此,结合生产需求,提出基于远道地震数据提取三维空间的泊松比信息,作为纵、横波数据之间的转换关系,进而获得泊松比约束的横波低频模型。具体步骤为:(1)优选对岩性敏感的地震波入射角;(2)反演泊松比弹性阻抗PEI;(3)建立横波低频模型。在白云深水区的勘探实践表明,由于初始模型更好地反映了地层岩性背景,减少了反演结果的异常值,2号砂体的平面分布与气/水边界吻合,与实钻结果一致,落实了储层分布,扩大了天然气探明储量,取得了较好的经济效益。

基于全波形反演速度约束的叠后地震反演方法

对于井数较少或者沉积相变化较快的地层,利用测井曲线建立的反演低频模型难以控制反演弹性参数的空间变化趋势。据此笔者发展了基于FWI速度约束的叠后地震反演方法,该方法充分利用了FWI速度的真三维信息,据此得到反演弹性参数的空间变化趋势。对于叠后地震反演所需要的纵波阻抗低频模型,提出了基于测井岩石物理拟合关系将FWI速度转换为FWI纵波阻抗的方法。另外,针对FWI纵波阻抗和测井纵波阻抗存在一定差异的问题,提出了FWI纵波阻抗均值校正方法,据此可得到较为准确的纵波阻抗低频模型。单井和实际工区应用表明,纵波阻抗反演结果和井上结果匹配性较高,因此笔者提出的基于FWI速度约束的叠后地震反演方法较为有效,可为储层预测提供较为有利的技术支持。

基于反演技术的碎屑岩高精度三维观测系统研究

塔里木盆地塔北地区碎屑岩油气资源丰富,是重要勘探区域之一。随着碎屑岩油气开发的深入,以往的低密度三维地震资料已不能满足碎屑岩薄砂岩等储层高精度刻画需求,亟需开展满足碎屑岩开发的高精度三维地震采集方法研究。依托塔北玉东区块三维地震采集资料,优选约束稀疏脉冲反演方法,基于波阻抗反演资料,开展了针对提高砂体刻画精度的观测系统参数研究。结果表明,地震剖面上对比不明显的砂岩弱反射,在波阻抗的反演资料上差异明显,丰富了碎屑岩地震采集方法的评价和优选手段;初步明确了观测系统参数优先选择顺序为炮道密度、面元、接收线距、观测宽度以及覆盖次数。参考现阶段炸药震源高密度采集经验,建议炮道密度应达到170×10^(4),较小的面元15 m×15 m,接收线距约为210 m,横纵比在0.7以上宽方位观测。研究结论为碎屑岩高精度三维地震采集观测系统研究和参数设计提供了有效的技术参考。

井旁道地震子波精细提取方法

如何由地震资料及测井资料确定井旁道地震子波是求取井旁道地层波阻抗的关键。本文在详细研究Ri-etsch确定地震子波长度方法的基础上,依据离散反演理论,并考虑到子波在空间变化的特点,提出了一种井旁道地震子波精细提取方法:1由多道相关法提取初始子波的振幅谱;2结合测井资料确定初始子波的相位谱;3根据离散反演理论。

稀疏脉冲和基于模型反演在王家岗沙四段砂岩油藏精细勘探中的应用

1998年 11月 ,胜利油田王家岗地区的第一口发现井 (WX119井 )在埋深 2 5 0 0～ 30 0 0 m的沙河街组沙四段砂岩中发现了高产工业油气流 ,随后如何进一步确定含油砂体展布范围和空间厚度变化成为对油藏作进一步评价和开发的关键。在研究区仅有 4口井的情况下 ,利用基于道的稀疏脉冲三维地震反演方法确定了含油砂体的分布范围及厚度变化 ,据此部署的 3口评价井和 1口探井都获得了高产工业油气流。根据与已知含油砂体的波阻抗特征的类比 ,对没有钻探的高阻抗区进行钻探以使含油气范围不断扩大。钻井数达 30口 ,其中仅 2口井失利。为了进一步搞清含油砂体分布范围 ,我们采用了基于地质模型的三维地震反演 ,对所钻遇的油层分布进行了预测 ,分析了失利井的原因 ,提供了新的钻探目标 。

不同围压下岩石中泊松比的各向异性

由弹性波纵横波速比计算得到的泊松比 ,在利用地震波反演地下结构和物质组成时 ,可以提供比单纯地利用纵波或者横波波速更强的约束 .为了研究不同岩石中泊松比及其各向异性随围压的变化 ,选取 1 9块典型的岩石样品 ,在不同围压下沿相互正交的 3个方向同时测量纵、横波速度 ,并通过计算得到了泊松比及其各向异性 .结果表明 ,在大部分样品中泊松比各向异性与纵波速度各向异性有一定的相关性 ,但在有的样品中泊松比各向异性与纵波速度各向异性没有明显的关系 ,甚至表现出完全相反的变化规律 .由于泊松比也表现出很强的各向异性 ,在排除微裂隙的影响后有的仍可以达到 30 %以上 ,在利用实际地震波传播数据通过泊松比反演地下物质结构时必须考虑其各向异性的影响 .

弹性阻抗在岩性与流体预测中的潜力分析

给出了弹性阻抗的概念,并根据弹性阻抗与波阻抗定义的相似性,提出了利用叠后测井约束反演方法实现弹性阻抗反演的思想。利用Gassmann方程对渤海湾地区上第三系储层进行了流体替代模拟,得出横波速度随水饱和度变化很小,纵波速度和密度随水饱和度变化较大,对流体变化较敏感的结论。用不同饱和度的纵、横波速度和密度参数,利用波动方程正演模拟得到叠前合成道集,并提取角道集剖面,然后反演得到弹性阻抗剖面。反演结果表明,利用叠后测井约束反演方法实现弹性阻抗反演是有效和可靠的。对弹性阻抗和波阻抗与水饱和度的关系进行了对比分析,结果表明,弹性阻抗可以更好地反映流体饱和度的变化,在岩性和流体的识别和预测中具有很大的潜力。对鄂尔多斯苏里格气田的实际资料进行了处理,发现入射角为16°时弹性阻抗与自然伽马有很好的相似性,因此利用16°入射角对应的弹性阻抗可以识别有效储层。此外,通过井点弹性阻抗与自然伽马的对比分析,可以确定区分有效储层的门槛值,如苏里格地区有效储层的弹性阻抗门槛值为2900。

子波反演与波阻抗反演

本文简述了子波反演与波阻抗反演的基本原理，用数值模拟算例表明了子波反演与波阻抗反演的正确性，并对该两种反演方法的稳定性进行了讨论。

利用基于Russell近似的弹性波阻抗反演进行储层描述和流体识别

本文基于Russell提出的多孔流体饱和弹性介质的佐普里兹方程形式的近似公式,借鉴弹性波阻抗的原理,推导了标准化的以流体因子f、拉梅常数μ和密度ρ表示的新的弹性波阻抗公式。通过反演可以直接从弹性波阻抗数据体中提取流体因子f和拉梅常数μ数据体,从而将弹性波阻抗与流体因子联系起来,兼顾了常规弹性波阻抗反演的高抗噪性以及利用流体因子识别流体的直观性,并且流体因子f的直接提取方法减少了间接计算的误差累积过程,为储层流体预测提供了一种新的途径。利用文中方法在SL油田Y3工区提取的流体因子f可以有效地区分出不同的流体类型,流体因子f对流体类型的敏感程度要优于其他常规属性,对沙二段储层流体的识别更加准确可靠,在储层流体识别与寻找剩余油方面显示了较好的应用效果。

约束稀疏脉冲反演在储层预测中的应用

海通集洼陷北部属于复杂断块区,地质建模比较困难,依赖于初始模型的常规反演方法难以获得精确的反演结果。而约束稀疏脉冲反演不依赖模型,其反演的精度取决于原始数据特征。为此,在海通集洼陷北部利用约束稀疏脉冲反演技术进行了储层预测。首先简单介绍了约束稀疏脉冲反演技术的基本原理及其实现方法,着重讨论了通过比较合成地震记录和原始道的吻合程度确定有关参数的原则;然后对砂体的发育情况进行了预测,其反演结果与井的钻探结果基本吻合。