依赖频率的裂缝孔隙介质弹性属性及影响参数

发布时间：2018-06-02 15:42

本文选题：裂缝介质 + 有限差分　；参考：《成都理工大学》2017年硕士论文

【摘要】：裂缝性油气藏等复杂油气藏是目前研究探索的热门方向,为了分析裂缝储层的地震特性,更好地解释地震资料信息,需要建立与实际地下介质接近的地质模型,结合恰当的正演技术来模拟裂缝介质的地震响应,了解地震波的传播规律,分析敏感参数对其地震属性的影响。基于此,本文主要研究的内容包括:(1)基于交错网格差分技术具有计算速度快,效率高等特点,可以利用该方法用于模拟地下介质的地震波传播。本文推导了不同介质的波动方程,计算相应的一阶速度-应力方程,并利用交错网格差分技术做正演分析,分别模拟了各向同性介质、各向异性介质、简化粘弹介质以及双相介质(Biot理论、改进BISQ理论)的地震记录。通过模拟的波场快照和单炮地震记录发现,各向异性介质出现横波分裂的现象,双相介质中产生慢纵波,且固相与液相中的慢纵波差异较大。(2)等效裂缝模型的介绍:包括Hudson模型、Schoenberg模型、Thomsen模型。上述模型都是单一裂缝模型,未考虑背景孔隙和流体的影响。在低频情况下,Gurevich基于线性滑动理论和Gassmann各向异性原理,推导出背景孔隙及含流体情况下双孔裂缝模型的弹性属性的计算方法。本文基于Gurevich等效裂缝介质模型,分析了在低频情况下,背景孔隙度、裂缝密度、流体类型对地震波传播的影响。从模拟结果得出,裂缝密度与背景孔隙的增加都会使介质的各向异性增强,而随着流体的体积模量的增加会降低介质的各向异性。模拟结果与数值分析的参数的影响结果一致。(3)在中观尺度下,为了分析裂缝孔隙介质中地震波发生频散与衰减的原因,本文基于Brajanovski模型,分析裂缝弱度及背景孔隙度在全频带内对纵波相速度和逆品质因子的影响。通过模拟结论可以看出,依赖频率的相速度有一个明显的释放现象,随着孔隙度的增加,其频散与衰减的程度会增加。当孔隙度接近于零的时候,其介质基本不发生频散与衰减;随着裂缝弱度的增加,其衰减的程度增大,衰减的峰值频率向低频方向移动。(4)在微观尺度下,本文基于Collet模型,推导了依赖频率的弹性属性的计算公式,计算不同入射角情况下依赖频率的相速度及逆品质因子,并分析了特征参数(裂缝密度、背景孔隙度及流体类型)对地震属性的影响。
[Abstract]:In order to analyze the seismic characteristics of fractured reservoirs and interpret seismic information better, it is necessary to establish a geological model close to the actual underground media in order to analyze the seismic characteristics of fractured reservoirs and other complex reservoirs, such as fractured reservoirs and other complex reservoirs. Combining the appropriate forward modeling technique to simulate the seismic response of fractured medium, the propagation law of seismic wave is understood, and the influence of sensitive parameters on its seismic attribute is analyzed. Based on this, the main contents of this paper include: (1) the staggered grid difference technique has the advantages of high computational speed and high efficiency, so it can be used to simulate seismic wave propagation in underground media. In this paper, the wave equations of different media are derived, the corresponding first-order velocity-stress equations are calculated, and the forward modeling of isotropic medium and anisotropic medium is done by using staggered grid difference technique. The seismic records of viscoelastic and biphase media are simplified and the BISQ theory is improved. Through the simulated wave field snapshots and single shot seismic records, it is found that shear wave splitting occurs in anisotropic medium and slow longitudinal wave is produced in two-phase medium. An introduction to the equivalent fracture model of solid phase and liquid phase: including Hudson model, Schoenberg model and Thomsen model. All the above models are single fracture models without considering the influence of background pores and fluids. Based on the linear sliding theory and the Gassmann anisotropy principle, the elastic properties of the two-pore fracture model in the case of background pore and fluid are derived at low frequency. Based on the Gurevich equivalent fracture medium model, the influence of background porosity, fracture density and fluid type on seismic wave propagation at low frequency is analyzed. It is concluded from the simulation results that the anisotropy of the medium increases with the increase of fracture density and background porosity, while the anisotropy of the medium decreases with the increase of the volume modulus of the fluid. In order to analyze the causes of frequency dispersion and attenuation of seismic waves in fractured porous media, this paper is based on Brajanovski model. The influence of fracture weakness and background porosity on P-wave phase velocity and inverse quality factor in the whole frequency band is analyzed. It can be seen from the simulation results that the frequency dependent phase velocity has an obvious release phenomenon and its dispersion and attenuation will increase with the increase of porosity. When porosity is close to zero, there is no dispersion and attenuation in the medium. With the increase of fracture weakness, the attenuation degree increases, and the peak frequency of attenuation moves to the low frequency direction. At the micro scale, this paper is based on the Collet model. The formula for calculating frequency dependent elastic properties is derived, the phase velocity and inverse quality factor of frequency dependent at different incident angles are calculated, and the effects of characteristic parameters (fracture density, background porosity and fluid type) on seismic attributes are analyzed.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13;P631.4

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