基于反射率法的TTI介质正演模拟

本文在平面波入射和全固态各向异性介质的假设条件下,推导了水平层状TTI介质中的频率—慢度域纵、横波反射/透射系数表达式,合成了截距时间—慢度(τ-p)域地震记录,分析了各向异性参数对反射纵、横波AVO特性的影响;利用τ-p变换和迭代相似系数加权相结合的方法合成了球面波,压制了积分截断效应。研究结果表明:①τ-p变换和迭代相似系数加权相结合的方法压制截断效应效果良好。②对于反射纵波,TTI介质中的θ、ε、δ参数既控制大角度入射,也控制小角度入射,VTI介质中ε控制大角度入射,δ控制小角度入射;对于反射横波,各向异性参数对AVO特性的影响规律还有待进-步研究。③受地下介质的各向异性影响,用不同的各向异性参数进行反射率法正演模拟得到的合成记录是不相同的,并且TTI介质反射率法得到的纵、横波合成记录不涉及解耦问题。模型测试证明本方法具有较高的精度和效率。

The modeling based on the reflectivity method in TTI media

With the assumption of incident plane wave and whole-solid anisotropic media,we derive the reflection/transmission coefficients for the TTI(Tilted Transverse Isotropy)horizontally-layered media in frequency-slowness domain,and analyze how the anisotropy parameters affect the AVO properties of the reflected primary wave and secondary wave from the synthesized seismogram inτ-pdomain.By means ofτ-ptransformation and iterative similarity coefficients weighting method, we can compose the spherical wave,and suppress the truncation effect from integration.The following understandings are obtained from the study:① It is efficient to suppress truncation effect from integration by combiningτ-ptransformation and iterative similar coefficients weighting method.② For reflected primary wave,parametersθ,ε,δin TTI media control wide-angle incident wave and also small-angle incident wave.In VTI media,εcontrols wide-angle incident wave,andδ controls small-angle incident wave.As to reflected secondary wave,it needs to be further studied about how AVO properties affected by anisotropy parameters.③ Due to the impact of anisotropy in the layer,different anisotropy parameters lead to different synthetic seismogram in the reflectivity method.Here,the synthetic seismogram of reflected primary wave and secondary wave using reflectivity method in TTI medium has nothing to do with decoupling problems.Model tests demonstrate that this proposed method enjoys high precision and efficiency.