基于各向异性流体替换的裂隙介质波传播特征研究

流体替换是利用地震资料进行地层各向异性特征分析和流体预测的基础。基于各向异性流体替换理论,研究了多孔隙垂直裂隙(HTI)介质中的波传播特性,分析了裂隙密度、法向与切向裂隙韧度比(Z_N/Z_T)以及流体饱和度的变化对多孔隙HTI介质的P波速度、横波分裂、各向异性参数以及反射系数特征的影响。研究表明,随着裂隙密度的增大,P波速度水平分量的减小量大于垂直分量的减小量;随着水饱和度的增加,各向异性参数减小,而P波速度和各向异性AVO梯度增大;不同的Z_N/Z_T对横波分裂的幅度和偏振方向有明显影响,在干燥与饱和状态下各向异性AVO梯度都随着Z_N/Z_T的增大而减小。

Fluid substitution is the basis of anisotropy analysis and fluid prediction by using seismic data.Based on the anisotropic fluid substitution theory,we studied the wave propagation characteristics in the porous vertical fracture (HTI) medium,and analyzed the fracture density,ratio of normal and tangential fracture toughness (Z_N/Z_T),as well as the influence of fluid saturation variation on P-wave velocity,S-wave splitting,anisotropic parameters and characteristics of the reflection coefficient of porous HTI medium.The research result shows that the reduction amount of the horizontal component is greater than the vertical component for P-wave velocity along with the crack density increasing,and the anisotropic parameters decreasing while the P-wave velocity and anisotropic AVO gradient increasing along with the water saturation increasing; moreover,different Z_N/Z_T has significant effect on the magnitude and polarization directions of the S-wave splitting,anisotropic AVO gradient decreases with Z_N/Z_T increasing in both dry and saturated reservoirs.