Reflection And Transmission Characteristic Of Elastic Waves In TTI Media

The reflection and transmission theory of plane elastic wave on the boundary of theelastic surface is the theoretical basis of seismic exploration. A significant application ofreflection coefficient is amplitude versus offset analysis. The traditional AVO analysis isbased on isotropic reflection coefficient. If there is anisotropy on the either side of interface,the traditional AVO analysis shows distortion. Therefore, the study on reflection andtransmission in the isotropy is beneficial undoubtedly. This thesis derives the3-D Zoeppritzequation of incident qP wave in TTI media and study azimuth AVO characteristic in TTImedia, then establish PP wave reflection coefficient formula in the tilted crack media andanalyze the influence of tilted crack parameters on PP wave reflection coefficient. Finally,using the least square method achieve the optimization of AVO analysis in TTI media.In the azimuth TTI media, P-SV wave and SH wave are coupled, which makes energydistribution on the horizontal interface in TTI media complicated. This thesis derives the3-DZoeppritz equation for incident qP wave in TTI media, based on3-D seismic wavepropagation theory in TTI media and the study of six waves which incident wave generated,and then study azimuth AVO characteristic in TTI media.The propagation of seismic wave in the crack rock is equaled to the propagation in thehomogeneous anisotropic media. This thesis derives PP-wave reflection coefficient in crackequivalent TTI media referring to Hudson’s theory. This formula intuitively builds therelationship between reflection coefficient and crack parameters. On the basis of this formula,this paper analyzes PP-wave reflection coefficient sensitivities of filling and crack density andsummarizes the change of PP-wave reflection coefficient with different crack dip.According to the relationship of symmetry axis direction of VTI, HTI and TTI in space,the symmetry axis direction of TTI media is decomposed to the transverse and verticaldirection in the thesis. Furthermore, the PP reflection coefficient formula in TTI media isexpressed linearly by the PP reflection coefficient in VTI media and HTI media. To make itsimpler, this thesis discusses no azimuth PP reflection coefficient formula optimization AVOin TTI media for one kind of typical geology model.In order to verify the accuracy and applicability of the derived reflection and transmission coefficient formula, this thesis makes multiple coverage forward modeling ofthree layers model constituted by isotropic, VTI, HTI or TTI media and conduct sphericaldiffusion compensation for CSP seismic record. And then sort CMP gather from105CSPseismic records. Finally extract the amplitude on the reflection interface. Through thecomparison between the extracted amplitude from forward modeling record and the computedvalue from derived PP reflection coefficient, we can see they coincide very well and draw theconclusion that derived reflection and transmission coefficient formula is accurate anddependable.