井地联合提取VTI介质各向异性参数

在新疆塔里木盆地某地区的宽方位三维地震数据中,VTI介质火成岩的各向异性和垂向速度变化引起非双曲线时差。通过对实际资料的系统分析,我们不能利用DMO反演法,移动震源VSP反演法和多偏移距VSP初至旅行时反演法提取Thomsen参数用于各向异性地震资料的处理。因此本文提出一个新的方法:运用地震资料和零偏移距VSP井求取火成岩的各向异性参数δ;在比较精确确定火成岩地层深度和厚度的情况下,利用偏移距VSP井,求取了各向异性参数ε,从而获得火成岩的瞬时各向异性参数η;充分考虑VTI介质垂向速度变化对时差曲线的影响,获得了各向异性参数ηeff。最后,利用所提取的各向异性参数,进行VTI介质各向异性速度分析和成像,成像质量得到明显改善。

Estimation of anisotropy parameters in VTI media from surface P-wave seismic data and VSP

Nonhyperbolic moveout caused by anisotropy and the vertical inhomogeneity of velocity in VTI media is routinely shown by the wide azimuth seismic data in some areas of Tarim Basin, northwest China. By conducting a systematic analysis, we have found that the DMO inversion, the walkway VSP inversion and the multi-offset VSP travel time inversion could not estimate the Thomsen anisotropic parameters used in anisotropic seismic data processing. We developed a new method: the instantaneous anisotropic parameter δ is attained from seismic data and one zero-offset VSP well; the anisotropic parameter ε is then acquired from four offset VSP wells on the base of the attained accurate depth to anisotropic igneous rock layer and thickness of the layer, so that instantaneous anisotropic parameter η is then obtained. Taking the effect of inhomogeneity of velocity into account, the anisotropic parameter η__(eff) is attained finally. The image is improved greatly by anisotropy velocity analysis in VTI media using the anisotropic parameters acquired.