一种新的各向异性弹性阻抗近似公式

New approximation formula for calculation of elastic impedance in anisotropic media.

1. 中国石油大学 CNPC 物探重点实验室, 北京102249;2. 中国石油化工股份有限公司勘探开发研究院, 北京100083

CNPC Key Lab of Geophysical Prospecting University of Petroleum,Beijing 102249,China

弹性阻抗是声波阻抗的拓展,可以更好地反映储层的性质。忽略各向异性影响的各向同性弹性阻抗公式不能正确地描述各向异性介质中弹性阻抗随入射角和方位角的变化。为此,在方位各向异性(HTI)介质模型的基础上,利用Connolly推导弹性阻抗的思想,根据各向异性反射系数近似公式,推导出了适合非零炮检距的各向异性弹性阻抗近似公式(简称新近似公式)。通过数值模拟,对纵波弹性阻抗随入射角和方位角的变化特征进行了描述．分析了各向异性参数对不同方位纵波弹性阻抗的影响．以及新近似公式的精度。分析结果表明,在弱各向异性介质且横波分裂参数γ不为0时,新近似公式比Martins近似公式的精度高。

Elastic impedance is the extension of acoustic impedance and describes the properties of reservoir more accurate.The formulae for isotropic elastic impedance neglecting the effects of seismic ani-sotropy can't describe accurately the variation of elastic impedance with incident angle and azimuth.On the basis of azimuthal anisot-ropy medium model,following the derivation of elastic Impedance from Patrick Connolly,according to approximation of anisotropic refection coefficient,a new approximate formula of elastic imped-ance in azimuth anisotropic media was derived suitable for nonzero offset (abbreviation of new approximation formula).Through nu-meral simulation,the variation of P wave elastic impedance with in-cident and azimuthal angle was described;the effect of anisotropic parameters on P wave elastic impedance in arbitrary azimuth and the precision of new approximation formula were analyzed.The re-sults show that new approximation formula is more accurate than the Martins' when it is in weak anisotropic media and the anisotrop-ic parameter is not zero.