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1.
裂隙性储层孔隙度与饱和度是油气藏评价的两个重要参数.本文提出利用裂隙介质AVO属性计算裂隙性储层孔隙度与饱和度的新方法.运用等效理论将裂隙介质等效为各向异性介质,得到裂隙介质的AVO响应即得到裂隙介质各向异性截距与梯度,根据各向异性截距梯度与孔隙度饱和度的关系得到裂隙介质的孔隙度和饱和度.本文建立裂隙介质(TTI介质)梯度截距和孔隙度饱和度的关系,可以根据地震数据直接求取裂隙介质的孔隙度和饱和度.模型试算表明,该方法能得到裂隙介质准确的孔隙度和饱和度,且稳定性较好. 相似文献
2.
长波长假设条件下,各向同性背景地层中发育一组平行排列的垂直裂缝可等效为具有水平对称轴的横向各向同性（HTI）介质.基于不同观测方位的岩石地震响应特征变化,宽方位地震数据不仅可实现裂缝岩石弹性参数与各向异性参数的预测,同时也蕴含着丰富的孔隙度等储层物性参数信息.本文结合实际地震资料提出了贝叶斯框架下岩石物理驱动的储层裂缝参数与物性参数概率地震联合反演方法,首先基于AVAZ反演裂缝岩石的弹性参数与各向异性参数,并在此基础上通过统计岩石物理模型表征孔隙度、裂缝密度等各向异性介质储层参数与裂缝岩石参数的相互关联,并采用马尔科夫链蒙特卡洛（MCMC）抽样方法进行大量样本的随机模拟,使用期望最大化（EM）算法估计后验条件概率分布,最终寻找最大后验条件概率对应的孔隙度、裂缝密度等HTI裂缝介质储层参数即为反演结果.测井及实际地震数据处理表明,该方法能够稳定合理地从方位地震资料中获取裂缝岩石弹性参数与各向异性参数,并提供了一种较为可靠的孔隙度、裂缝密度等裂缝介质储层参数概率地震反演方法. 相似文献
3.
裂缝型储层的描述包括预测裂缝分布特征和识别裂隙充填物.依据等效介质理论计算的纵波速度随裂缝密度的增大而减小.正演地震记录显示,裂缝介质含气时反射振幅最大,且变化程度比含油或含水时大.叠前方位AVO反演所得的各向异性梯度Bani与裂缝密度成正比,可用于描述有效裂缝发育强度.对于不同的裂缝密度,各向异性梯度Bani与各向同性梯度Biso的比值I(1)fluid近似为常数,且对流体敏感.经裂缝纵横比和背景介质拉梅常数修正后,流体因子Ifluid既不随纵横比变化,又不受背景介质的影响,是裂缝型储层敏感的流体识别因子.在塔里木盆地塔北哈拉哈塘地区热瓦普区块碳酸盐岩储层裂缝发育区域,运用该参数在井点处的流体识别效果与钻井结果一致. 相似文献
4.
在裂缝诱导各向异性理论研究中通常使用等效HTI介质来近似多组裂缝所引起的综合效应.由于构造运动的复杂性,多组裂缝普遍存在于地壳与油气储层中.为了研究多组裂缝的地震属性特征,分析常用的等效HTI模型对于多组裂缝近似精度及附加裂缝对介质属性特征的影响,本文利用线性滑移模型进行了多组垂直裂缝的单斜各向异性等效介质理论计算,并利用空间搜索方法求取与其最为接近的HTI介质各向异性弹性参数.重点研究了在两种各向异性介质中纵波速度、快慢横波速度和极化特征及其差异,量化分析附加裂缝对于地震属性如速度、极化方向和走时等的影响,研究对附加裂缝敏感的地震属性.此研究结果和方法为进一步研究多组裂缝的反演及识别方法提供基础,同时对于将高阶对称性各向异性介质中已存在的计算方法应用于低阶对称性时的适用程度、精度分析及相关方法研究具有重要作用. 相似文献
5.
油气勘探实践表明, 裂缝是油气的储存空间或运移通道, 裂缝介质地震波场的研究越来越受到关注. 实际地层中裂缝形成受多种因素控制, 物理属性比较复杂, 表现出强烈的各向异性. 由于上覆地层的压力使得水平或低陡倾角裂缝存在较少, 大多数为高陡倾角裂缝, 利用线性滑动裂缝介质的等效理论将高陡倾角裂缝介质等效为横向各向同性介质, 便于实际应用. 本文采用各向异性弹性波旋转交错网格模拟方法对含裂缝介质单炮记录进行模拟与分析. 结果表明: 裂缝的存在相当于人为增加反射界面; 裂缝密度越大, 裂缝纵横比越小, 裂缝充填物与背景介质弹性性质差别越大, 引起的反射波能量变化越大. 本文模拟结果为利用地震数据进行裂缝介质参数反演与储层识别及油气预测提供了依据. 相似文献
6.
基于长波长近似假设,周期性薄互层中发育一组平行排列的垂直裂缝则可视为等效的正交各向异性介质.岩石物理是构建裂缝参数与地震响应之间联系的基础,地震散射理论是各向异性介质参数反演的有效途径.文章提出了一种利用方位叠前地震数据实现正交各向异性裂缝储层Thomsen弱各向异性参数与裂缝弱度参数可靠预测的方法.首先,综合考虑矿物基质、孔隙、裂缝及各向异性岩石中流体替换的影响,通过构建正交各向异性裂缝岩石物理等效模型,实现正交各向异性刚度系数的估测,进而预测储层测井数据的弹性参数、Thomsen弱各向异性参数及裂缝弱度参数,为后续地震反演提供初始模型约束;然后,基于地震散射理论,推导了面向Thomsen弱各向异性参数与裂缝弱度参数反演的正交各向异性介质纵波反射系数方程,为后续地震反演奠定了理论基础;最后,发展了贝叶斯框架下的正交各向异性裂缝储层Thomsen弱各向异性参数与裂缝弱度参数AVAZ反演方法,同时考虑柯西稀疏约束正则化和平滑模型约束正则化约束,使用非线性的迭代重加权最小二乘策略实现正交各向异性特征参数的稳定估算.模型和实际资料处理表明,该方法能够稳定可靠地从方位叠前地震资料中获取正交各向异性特征参数,为正交各向异性介质的特征参数预测提供了一种高可靠性的地震反演方法. 相似文献
7.
在长波长假设条件下,水平层状地层中发育一组垂直排列的裂缝构成了等效正交各向异性介质.各向异性参数与裂缝弱度参数的估算有助于非均匀各向异性介质的各向异性特征描述,而弹性逆散射理论是非均匀介质参数反演的有效途径.基于地震散射理论,我们首先推导了非均匀正交介质中纵波散射系数方程,并通过引入正交各向异性特征参数,提出了一种新颖的正交各向异性方位弹性阻抗参数化方法.为了提高反演的稳定性与横向连续性,我们发展了贝叶斯框架下的正交各向异性方位弹性阻抗反演方法,同时考虑了柯西稀疏约束正则化和平滑模型约束正则化,最终使用非线性的迭代重加权最小二乘策略实现了各向异性特征参数的稳定估算.模型和实际资料处理表明,反演结果与测井解释数据相吻合,证明了该方法能够稳定可靠地从方位叠前地震资料中获取各向异性特征参数,减小参数估算的不确定性,为非均匀正交介质的各向异性预测提供了一种高可靠性的地震反演方法. 相似文献
8.
裂缝储层岩石物理参数的准确获得对地下裂缝预测具有重要意义,而叠前方位AVA地震反演是获得裂缝岩石物理参数的有效手段.假设地下岩石为倾斜横向各向同性（TTI）介质,本文从裂缝岩石物理等效模型的构建出发,从测井数据中估计出纵横波相对反射系数和裂缝柔度参数.通过推导含裂缝柔度的方位各向异性反射系数公式,基于贝叶斯反演框架建立了P波线性AVAZ反演方法.合成地震数据应用表明基于贝叶斯理论的TTI介质裂缝柔度反演方法具有一定抗噪性,可以降低裂缝柔度估测的不确定性,为地下裂缝预测提供有力的依据. 相似文献
9.
裂缝储层岩石物理参数的准确获得对地下裂缝预测具有重要意义,而叠前地震反演是获得裂缝岩石物理参数的有效手段.本文从裂缝岩石物理等效模型的构建出发,从测井数据上估测了裂缝岩石物理参数,通过推导含裂缝岩石物理参数的方位各向异性弹性阻抗公式,探讨了基于方位各向异性弹性阻抗的裂缝岩石物理参数地震反演方法.实际工区地震数据应用表明,基于方位各向异性弹性阻抗的裂缝岩石物理参数反演方法合理、可靠,可以降低裂缝岩石物理参数估测的不确定性,为地下裂缝预测提供有力的依据. 相似文献
10.
裂缝预测是页岩气甜点预测的重要内容.页岩气储层高角度裂缝发育,具有明显的HTI介质各向异性特征,基于各向异性参数与裂缝密度的相关性,提出了一种裂缝密度反演的新方法.首先推导了一种能反映裂缝密度的方位AVO近似公式及其方位弹性阻抗方程(EVAAz方程);然后应用贝叶斯理论,形成了组稀疏方位弹性阻抗反演目标泛函,在此基础上通过阻尼最小二乘算法求解弹性矩阵,稳健得到了剪切模量、法向弱度与切向弱度;最后应用裂缝弱度与裂缝密度的关系,实现了裂缝密度的定量预测.经实际数据试验,预测结果与页岩压裂参数吻合度高,证实该方法是有效的. 相似文献
11.
Based on the long-wavelength approximation, a set of parallel vertical fractures embedded in periodic thin interbeds can be regarded as an equivalent orthorhombic medium. Rock physics is the basis for constructing the relationship between fracture parameters and seismic response. Seismic scattering is an effective way to inverse anisotropic parameters. In this study, we propose a reliable method for predicting the Thomsen’s weak anisotropic parameters and fracture weaknesses in an orthorhombic fractured reservoir using azimuthal pre-stack seismic data. First, considering the influence of fluid substitution in mineral matrix, porosity, fractures and anisotropic rocks, we estimate the orthorhombic anisotropic stiffness coefficients by constructing an equivalent rock physics model for fractured rocks. Further, we predict the logging elastic parameters, Thomsen’s weak parameters, and fracture weaknesses to provide the initial model constraints for the seismic inversion. Then, we derive the P-wave reflection coefficient equation for the inversion of Thomsen’s weak anisotropic parameters and fracture weaknesses. Cauchy-sparse and smoothing-model constraint regularization taken into account in a Bayesian framework, we finally develop a method of amplitude variation with angles of incidence and azimuth (AVAZ) inversion for Thomsen’s weak anisotropic parameters and fracture weaknesses, and the model parameters are estimated by using the nonlinear iteratively reweighted least squares (IRLS) strategy. Both synthetic and real examples show that the method can directly estimate the orthorhombic characteristic parameters from the azimuthally pre-stack seismic data, which provides a reliable seismic inversion method for predicting Thomsen’s weak anisotropic parameters and fracture weaknesses. 相似文献
12.
Attempts have previously been made to predict anisotropic permeability in fractured reservoirs from seismic Amplitude Versus Angle and Azimuth data on the basis of a consistent permeability‐stiffness model and the anisotropic Gassmann relations of Brown and Korringa. However, these attempts were not very successful, mainly because the effective stiffness tensor of a fractured porous medium under saturated (drained) conditions is much less sensitive to the aperture of the fractures than the corresponding permeability tensor. We here show that one can obtain information about the fracture aperture as well as the fracture density and orientation (which determines the effective permeability) from frequency‐dependent seismic Amplitude Versus Angle and Azimuth data. Our workflow is based on a unified stiffness‐permeability model, which takes into account seismic attenuation by wave‐induced fluid flow. Synthetic seismic Amplitude Versus Angle and Azimuth data are generated by using a combination of a dynamic effective medium theory with Rüger's approximations for PP reflection coefficients in Horizontally Transversely Isotropic media. A Monte Carlo method is used to perform a Bayesian inversion of these synthetic seismic Amplitude Versus Angle and Azimuth data with respect to the parameters of the fractures. An effective permeability model is then used to construct the corresponding probability density functions for the different components of the effective permeability constants. The results suggest that an improved characterization of fractured reservoirs can indeed be obtained from frequency‐dependent seismic Amplitude Versus Angle and Azimuth data, provided that a dynamic effective medium model is used in the inversion process and a priori information about the fracture length is available. 相似文献
13.
结合有限差分方法和等效介质理论，模拟了离散分布裂缝介质中地震波的传播. 基于等效介质理论，利用二维有限差分实现封闭裂缝的离散分布；裂缝可以处理成固体岩石中的高度柔性界面，并可以用线性滑动或者位移间断模型进行裂缝的物理描述. 对于含有多组裂隙的破裂固体，其有效柔度可以认为是固体骨架背景柔度和裂缝附加柔度之和. 在一阶近似条件下，固体骨架和裂缝参数可以通过有效各向异性系数联系起来，有效各向异性系数决定了各向异性（裂缝效应）对于地震波传播的影响. 通过与射线理论方法的对比检验，说明本文提出的模拟方法的有效性，并通过几个数值算例说明本方法可有效模拟不同的裂缝分布效应. 结果表明，即使在裂缝密度很小的情况下，具有相同裂缝密度的不同的空间分布可以产生不同的波场特征. 同时，也验证了不同裂缝尺度对波长的不同影响，以及裂缝尺度具有幂率分布（分形）时，尺度对波场的影响. 最后得出结论：在运用建立在等效介质理论基础上的地震各向异性概念来描述裂缝固体的特征时，要倍加小心，等效介质理论中尚未合理处理的裂缝尺度和空间分布对波的传播特征具有重要的影响. 相似文献
14.
Seismic amplitude variation with offset and azimuth (AVOaz) inversion is well known as a popular and pragmatic tool utilized to estimate fracture parameters. A single set of vertical fractures aligned along a preferred horizontal direction embedded in a horizontally layered medium can be considered as an effective long-wavelength orthorhombic medium. Estimation of Thomsen’s weak-anisotropy (WA) parameters and fracture weaknesses plays an important role in characterizing the orthorhombic anisotropy in a weakly anisotropic medium. Our goal is to demonstrate an orthorhombic anisotropic AVOaz inversion approach to describe the orthorhombic anisotropy utilizing the observable wide-azimuth seismic reflection data in a fractured reservoir with the assumption of orthorhombic symmetry. Combining Thomsen’s WA theory and linear-slip model, we first derive a perturbation in stiffness matrix of a weakly anisotropic medium with orthorhombic symmetry under the assumption of small WA parameters and fracture weaknesses. Using the perturbation matrix and scattering function, we then derive an expression for linearized PP-wave reflection coefficient in terms of P- and S-wave moduli, density, Thomsen’s WA parameters, and fracture weaknesses in such an orthorhombic medium, which avoids the complicated nonlinear relationship between the orthorhombic anisotropy and azimuthal seismic reflection data. Incorporating azimuthal seismic data and Bayesian inversion theory, the maximum a posteriori solutions of Thomsen’s WA parameters and fracture weaknesses in a weakly anisotropic medium with orthorhombic symmetry are reasonably estimated with the constraints of Cauchy a priori probability distribution and smooth initial models of model parameters to enhance the inversion resolution and the nonlinear iteratively reweighted least squares strategy. The synthetic examples containing a moderate noise demonstrate the feasibility of the derived orthorhombic anisotropic AVOaz inversion method, and the real data illustrate the inversion stabilities of orthorhombic anisotropy in a fractured reservoir. 相似文献
15.
Understanding the effects of in situ fluid content and fracture parameters on seismic characteristics is important for the subsurface exploration and production of fractured porous rocks. The ratio of normal-to-shear fracture compliance is typically utilized as a fluid indicator to evaluate anisotropy and identify fluids filling the fractures, but it represents an underdetermined problem because this fluid indicator varies as a function of both fracture geometry and fluid content. On the bases of anisotropic Gassmann's equation and linear-slip model, we suggest an anisotropic poroelasticity model for fractured porous reservoirs. By combining a perturbed stiffness matrix and asymptotic ray theory, we then construct a direct relationship between the PP-wave reflection coefficients and characteristic parameters of fluids(P-and S-wave moduli) and fractures(fracture quasi-weaknesses), thereby decoupling the effects of fluid and fracture properties on seismic reflection characterization.By incorporating fracture quasi-weakness parameters, we propose a novel parameterization method for elastic impedance variation with offset and azimuth(EIVOA). By incorporating wide-azimuth observable seismic reflection data with regularization constraints, we utilize Bayesian seismic inversion to estimate the fluid content and fracture parameters of fractured porous rocks. Tests on synthetic and real data demonstrate that fluid and fracture properties can be reasonably estimated directly from azimuthal seismic data and the proposed approach provides a reliable method for fluid identification and fracture characterization in a gas-saturated fractured porous reservoir. 相似文献
16.
In this paper we propose a method for the characterization of naturally fractured reservoirs by quantitative integration of seismic and production data. The method is based on a consistent theoretical frame work to model both effective hydraulic and elastic properties of fractured porous media and a (non‐linear) Bayesian method of inversion that provides information about uncertainties as well as mean (or maximum likelihood) values. We model a fractured reservoir as a porous medium containing a single set of vertical fractures characterized by an unknown fracture density, azimuthal orientation and aperture. We then look at the problem of fracture parameter estimation as a non‐linear inverse problem and try to estimate the unknown fracture parameters by joint inversion of seismic amplitude versus angle and azimuth data and dynamic production data. Once the fracture parameters have been estimated the corresponding effective stiffness and permeability tensors can be estimated using consistent models. A synthetic example is provided to clearly explain and test the workflow. It shows that seismic and production data complement each other, in the sense that the seismic data resolve a non‐uniqueness in the fracture orientation and the production data help to recover the true fracture aperture and permeability, because production data are more sensitive to the fracture aperture than the seismic data. 相似文献
17.
Frequency-dependent amplitude variation with offset offers an effective method for hydrocarbon detections and analysis of fluid flow during production of oil and natural gas within a fractured reservoir. An appropriate representation for the frequency dependency of seismic amplitude variation with offset signatures should incorporate influences of dispersive and attenuating properties of a reservoir and the layered structure for either isotropic or anisotropic dispersion analysis. In this study, we use an equivalent medium permeated with aligned fractures that simulates frequency-dependent anisotropy, which is sensitive to the filled fluid of fractures. The model, where pores and fractures are filled with two different fluids, considers velocity dispersion and attenuation due to mesoscopic wave-induced fluid flow. We have introduced an improved scheme seamlessly linking rock physics modelling and calculations for frequency-dependent reflection coefficients based on the propagator matrix technique. The modelling scheme is performed in the frequency-slowness domain and can properly incorporate effects of both bedded structure of the reservoir and velocity dispersion quantified with frequency-dependent stiffness. Therefore, for a dispersive and attenuated layered model, seismic signatures represent a combined contribution of impedance contrast, layer thickness, anisotropic dispersion of the fractured media and tuning and interference of thin layers, which has been avoided by current conventional methods. Frequency-dependent amplitude variation with offset responses was studied via considering the influences of fracture fills, layer thicknesses and fracture weaknesses for three classes amplitude variation with offset reservoirs. Modelling results show the applicability of the introduced procedure for interpretations of frequency-dependent seismic anomalies associated with both layered structure and velocity dispersion of an equivalent anisotropic medium. The implications indicate that anisotropic velocity dispersion should be incorporated accurately to obtain enhanced amplitude variation with offset interpretations. The presented frequency-dependent amplitude variation with offset modelling procedure offers a useful tool for fracture fluid detections in an anisotropic dispersive reservoir with layered structures. 相似文献