基于各向异性理论的裂隙介质正反演方法研究

发布时间：2018-03-03 11:41

本文选题：等效理论　切入点：各向异性　出处：《中国石油大学(华东)》2015年博士论文　论文类型：学位论文

【摘要】：裂缝是特殊岩性储层(碳酸盐,页岩等)的重要储集空间和运移通道,围绕裂隙介质的正反演研究对于深入了解地球介质结构、勘探开发复杂油气藏和监测预报地质灾害等具有重要理论意义和现实意义。本文基于裂缝等效理论深入研究了裂隙介质正反演方法,推导了裂缝介质地震波传播特征(相速度、群速度与偏振方向)的精确与近似表达式,建立了裂缝介质三维qP波波动方程有限差分数值模拟算法,研究了裂隙参数的反演策略和方法。基于线性滑动等效理论的模型参数化是实现裂隙介质正反演问题的理论基础。本文采用等效理论将裂隙介质等效为各向异性介质的研究思路,并考虑地下压力的存在使得裂隙介质中的裂缝通常为高陡倾角裂缝的特点,利用线性滑动与Hudson相结合的等效理论将单组裂缝等效为HTI介质,将两组正交裂缝等效为正交各向异性介质,将两组斜交裂缝等效为单斜各向异性介质,推导了三类不同裂隙介质的等效各向异性参数定量表达式,利用Thomsen参数对等效后的各向异性参数进行弱各向异性近似,从而建立起裂隙介质正反演的理论基础。地震波的传播特征(速度与偏振方向)是开展裂隙介质正反问题研究的核心方面。地震波传播速度作为研究地震波传播规律和描述介质特征的重要参数,主要包括相速度与群速度。本文利用弹性动力学三个基本方程即广义虎克定律、运动微分平衡方程及几何方程推导了三类裂隙介质的Christoffel方程,通过求解Christoffel方程的特征值得到了裂隙介质的相速度表达式,以裂隙介质相速度为基础,利用Berryman方程与Crampin方程推导了裂隙介质的群速度表达式,通过求解Christoffel方程的特征向量得到了裂隙介质的偏振方向表达式,并利用Thomsen参数实现了相速度与偏振方向的弱各向异性近似。qP波波动方程地震正演模拟是研究裂隙介质中地震波传播规律与地震响应特征的重要方法。本文根据弹性动力学三个基本方程即广义虎克定律、运动微分平衡方程及几何方程推导了裂隙介质的弹性波方程,结合Alkhalifah声学近似假设原理(令横波速度为零)求取了裂隙介质的qP波波动方程,利用有限差分原理将qP波微分方程转化为qP波差分方程,采用完全匹配层边界条件推导了裂隙介质带有PML边界的有限差分方程。选用层状模型和凹陷模型进行了正演模拟验证了该数值模拟精度和准确度,分析研究了不同模式裂隙介质的地震响应特征,讨论了不同裂缝参数(裂缝密度、裂缝长度、裂缝宽度与裂缝充填物)与地震波场特征的关系,并进一步利用逆时偏移结果验证了正演模拟方法的正确性。叠前地震反演是获取裂隙参数和认知地下裂缝的有效手段。本文利用裂隙介质弹性波相速度与偏振方向,建立了入射波、反射波与透射波的波函数,结合snell定律与介质分界面处的应力连续和位移连续边界条件,构建了qP波入射裂隙介质弹性波分界面的拟Zoeppritz方程,根据弱各向异性近似与弹性界面的相似近似推导了qP波入射的近似反射系数,分析研究了裂缝参数的AVOZ特征。在此基础上利用最小二乘的反演策略实现了基于两个方位地震数据反演裂缝参数的方法,并进一步针对模型数据通过波形反演方法完成了背景纵波速度的反演研究工作。
[Abstract]:Crack is a special lithologic reservoir (carbonate, shale) in space and the important migration channels around the reservoir, inversion of fractured media research is to understand the earth medium structure, has important theoretical significance and practical significance in the exploration and development of complex oil and gas reservoirs and geological disaster monitoring and forecasting. In this paper, in-depth study of the theory of equivalent crack fracture the medium is derived based on inversion method, seismic wave propagation characteristics of fractured medium (phase velocity, group velocity and polarization direction) of the exact and approximate expressions, establish fractured medium 3D qP wave equation finite difference numerical simulation algorithm, inversion strategy and method to study the fracture parameters. The model parameters of the equivalent linear sliding theory based on the basic theory of the realization of fractured medium and inversion problem. This paper uses the theory of equivalent fracture medium equivalent to the research of anisotropic media, and to consider The presence of pressure makes the fracture medium usually characteristics of high steep crack, using the equivalent linear sliding theory combined with Hudson single group crack equivalent to HTI medium, two groups of orthogonal cracks equivalent to orthotropic medium, two sets of oblique cracks using monoclinic anisotropic media. The quantitative formula of equivalent anisotropic parameters are deduced with three different types of fracture medium, the anisotropic parameter equivalent of weak anisotropy approximation using Thomsen parameters, so as to establish the theoretical basis of fractured medium inversion. The characteristics of seismic wave propagation (velocity and polarization direction) is the core of the research problem and medium cracks. As an important parameter of propagation velocity of seismic wave propagation and describing the media characteristics of seismic waves, including the phase velocity and group velocity. This paper using the elastic dynamics of three The basic equations of the generalized Hooke's law, the differential equilibrium equations and geometric equations deduced the Christoffel equation of the three kind of fractured media, the characteristics of the solution of the Christoffel equation to the fracture medium phase velocity expressions in fractured medium phase velocity as the basis, using Berryman equation and Crampin equation deduced the group velocity expression of fractured media, the the feature vector for solving Christoffel equations has been the polarization direction of the fracture media expression, and the use of Thomsen parameters to achieve weak anisotropic phase velocity and polarization direction of the approximate.QP wave equation seismic forward modeling is an important method for the response characteristics of seismic wave propagation and seismic study of fractured medium. According to the three basic equations of elastic dynamics the generalized Hooke's law, the differential equilibrium equations and geometric equations derived fracture medium elastic wave. The process, combined with the Alkhalifah approximation principle (the acoustic shear wave velocity is zero) for qP wave equation for fractured media, using finite difference qP wave differential equations into difference equations of qP wave principle, the perfectly matched layer boundary conditions are deduced by finite difference fracture medium with PML boundary integral equation is selected. Layered model and depression model for forward simulation to verify the precision and accuracy of the numerical simulation and analysis of response characteristics of different models of fractured medium earthquake, different crack parameters were discussed (crack density, crack length, crack width and crack filling) and seismic wave field characteristics, and further use of the inverse when the migration results verified the correctness of the forward simulation method. The prestack seismic inversion is an effective method to obtain the fracture parameters and fracture cognition. This paper uses the elastic fracture medium wave phase velocity and polarization The establishment of the incident wave direction, wave functions, wave and transmission wave reflection, combined with the stress of Snell's law and the continuous medium interface and continuous displacement boundary conditions, construct the quasi Zoeppritz equation between wave fracture medium elastic wave qP, according to the weak anisotropy approximation and approximation derived approximate reflection coefficient of qP wave incident similar elastic interface, AVOZ to study the characteristics of fracture parameter analysis. On the basis of using the least squares inversion strategy realization method of two azimuth seismic data based on the inversion of fracture parameters, and further the data of model by waveform inversion method to complete the work of inversion of P-wave velocity background.

【学位授予单位】：中国石油大学(华东)
【学位级别】：博士
【学位授予年份】：2015
【分类号】：P631.4

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