地震正演模型应用(Ⅱ):用地震正演叠前炮集记录模拟方法定量解释薄砂岩的各向异性(英文)

Applied seismic forward modeling(part Ⅱ): Quantitative determination of thin layer anisotropy by pre-stack seismic forward modeling

叠前地震正演模拟可以获得比叠后正演更多的有用信息,例如能够用于含有各向异性特征的精细速度建模的信息。塔里木盆地下石炭统存在砂泥岩互层,偶见石膏、砾岩和煤层。砂泥岩薄互层中的速度差异可能导致各向异性,但是利用常规的地震方法很难识别和定量描述各向异性。由叠前各向同性正演获得的炮集,证明砂泥岩中存在各向异性,通过迭代生成的理论合成炮集与实际原始炮集相对比,可以定量描述各向异性,结果证明在该区砂泥岩层存在5%的横向各向同性,其高速传播方向为水平面。

Pre-stack seismic modeling reveals information unattainable from post-stack seismic modeling, for example which can be used to refine a velocity model by the inclusion of anisotropy. The sandstone-mudstone member of the Tarim Basin is a Lower Carboniferous interbedded sandstone and mudstone, with occasional interbeds of gypsum, conglomerate, and coal. It has been suspected that the sandstone-mudstone member may be anisotropic due to the thin interbedding of contrasting velocity beds, but verifying and quantifying the anisotropy is difficult with conventional seismic techniques. Pre-stack isotropic modeling of seismic shot gathers however proves that the sandstone-mudstone member is anisotropic. Iterative modeling whereby synthetic pre-stack shot gathers are compared with the original shot-gather can be used to quantify the anisotropy, showing that the sandstone mudstone member is approximately 5% transversely isotropic, with a fast horizontal plane. Figure 4 reference 9.