【作者】 刘前坤；

【导师】 韩立国；

【作者基本信息】 吉林大学 ， 地球探测与信息技术， 2008， 博士

【摘要】 方位各向异性AVO理论是进行裂隙储层预测的重要理论基础。HTI介质中方位纵波AVO反射系数的提出后,一系列纵波检测裂隙,估算裂隙密度方法大量涌现出来。相对而言,方位各向异性介质转换波AVO的研究方面却发展缓慢,其主要原因就是因为没有明确简洁的转换波反射系数公式,这一点不仅大大限制了方位各向异性介质中转换波AVO研究,同时也影响了联合PP波进行联合反演,以及弹性波阻抗反演等一系列问题的深入开展。针对这个问题,本文引入常用的等效Thomsen各向异性参数对公式进行了推导,得到了更为简单实用的反射系数近似公式,并对新公式的AVO属性进行了研究。在此基础上,推导了PP波和PS波弹性波阻抗方程,把入射角和方位角引入弹性波阻抗公式,拓宽了弹性波阻抗的应用范围。岩石物理学基础研究是AVO技术中关键一环。它是各种地震数据准确转换成为岩性、物性、含油气性等有用的地质信息的桥梁,本文建立了Gassmann孔隙流体-HTI模型,分析了孔隙度、含气饱和度和各向异性参数变化对地层AVO的影响。更多还原

【Abstract】 Fractured reservoirs are becoming more and more important in petrol exploration and development .To find fracture is main task in fracture formation .Identify and prediction of fracture and its developmental zone is meaningful to reservoir exploration and development .According to solid mechanics ,fracture strata is anisotropic media .For this reason ,the theory of anisotropy is the foundation of the theory of fracture .VTI and HTI model are the ideal anisotropic model . Horizontally transverse isotropic with the horizontal axis of symmetry (HTI) media is the simplest azimuthal anisotropic model used to describe realistic fractured reservoirs, which is one of the most effective model for studying seismic characterization of fractures .Recent advances show that it is therefore important to obtain fracture developmental zones , fracture strike and crack density from PP wave and PS converted wave seismic data .However ,the development of PS wave AVO analysis in azimuthal anisotropic media is slow. The main problem is lack of the simple and brief PS wave reflection coefficient equation .Still ,the most inversion of combined the PP wave and PS wave , and inversion of elastic impendence in anisotropic media are limited for this reason.Cherepanov and Nefedkina (2004)have derived the approximate linearized solution for PS wave reflection coefficient for the first time using assumption that elastic parameters contrast at separating interface and anisotropy are weak. But the parameters in the equation are not easy to use. In order to resolve this problem, the new approximate PS wave reflection coefficient has been obtained by the Thomsen anisotropic parameters. The simple relationship between the reflection amplitudes and anisotropic coefficients given here can be regarded as helpful rules of thumb in quickly evaluating the importance of anisotropy in a particular application.Then we discuss the effect of new reflection coefficient to three kind of gas sand AVO model .It is visible tools to identify the AVOⅢgas sand .The effect of three Thomsen parameters to PS wave reflection show that the effect of shear-wave splitting parameterγ(V) is strongest and the effect of anisotropy coefficientε(V) weakest in three parameters. And the effect of three parameters vary with azimuthal angle .The less of azimuthal angle ,the stronger of the effect .Based on the new approximation reflection coefficient in HTI media by the Thomsen anisotropic parameters, the attributes of AVO and characteristics of AVO background trends crossplotting of density ,S-wave velocity contrast and shear modulus have been described . It will be helpful to AVO interpretation in complicate condition.Petrophysics theory is the key of AVO technology .It is the bridge of well ,geology and seismic .we can get the geological information from the seismic data,such as lithological character ,physical property and hydrocarbon showing. Wherefore ,we introduce the Gassmann theory , postulation condition and the method of fluid substitution .Furthermore ,we study the effect of the porosity ,saturation and Thomsen anisotropic parameters to PS wave reflection coefficients in HTI-Isotropic pore reservoir model. The results show that the effect of porosity and anisotropic parameters is much stronger than that of saturation.And effect of porosity is a little stronger than that of anisotropic parameters.These conclusion are of significance in PS wave AVO analysis and elastic AVO theoretical investigation.Acoustic impedance (AI) will produce the ambiguity as the hydrocarbon indictor in the complicated reservoir .Using a simple linear formalism, Connolly (1999) introduced the concept of elastic impedance(EI) to allow investigating AVO anomalies at wide-angle regions of incidence. Because the resulting formula explicitly depends on medium parameters, the advantage of EI is often regarded as a rock attribute analogous to AI but for varying incidence angle ranges. Then S impedance(SEI) and PS impedance are obtained .This integration strategy is great helpful to the effect of AVO. Then ,the PP and PS wave elastic impendence in anisotropic media is derived for the first time in this paper. The advantage of new elastic impedance is that introduced the concept of elastic impedance(EI) to allow investigating AVO anomalies at wide-angle regions of incidence and azimuthal angle with the effect of anisotropic parameters .Then ,we can analysis the difference of elastic impedance with azimuthal angle and anisotropic parameters .Especially , we can study the variation of elastic impedance in 3D space .Furthermore , the effect of Thomsen anisotropic parameters to elastic impendence and fluid factor are described .On the basis of these results,we have obtained PP wave elastic impedance is sensitive to the variation of anisotropic parameters.on the contrast , PS wave elastic impedance is immunity to the anisotropic parameters.It has been carried out that variation of PP and PS wave elastic impedance to three kind of typical AVO model.Our previous work provide that new PP wave elastic impedance is only sensitive to AVOⅢ。New PS wave elastic impedance is sensitive to all of three typical AVO model.更多还原