含裂缝致密砂岩多波AVO响应分析

研究含裂缝致密砂岩的AVO响应特征，对致密砂岩储层参数的预测及油气开发具有重要意义。本文基于Biot-Gassmann流体替换理论，利用Thomsen各向异性理论建立含裂缝致密砂岩的等效HTI地震模型，通过分析含裂缝致密砂岩的PP、PS1、PS2波AVO响应特征发现：各向异性与各向同性介质的PP波反射系数在入射角小于10°时无明显差别，入射角大于10°时，不同裂缝密度致密砂岩的反射系数会有明显差异，且随裂缝密度增高而变大；各向异性与各向同性介质的PS波反射系数在入射角为0°、55°时两者几乎无差别；不同裂缝密度时PP波与PS1、PS2波AVA的极性反转位置移动规律不同。

Multi-wave AVO responses in fractured tight sandstone

AVO responses in fractured tight sandstone can provide useful evaluation parameters for tight sandstone reservoirs,which are significant to the petroleum production.Based on Biot-Gassmann's fluid substitution,we build horizontal transversely isotropic (HTI) model equivalent to fractured tight sandstone with Thomsen's weak seismic anisotropy theory,and analyze AVO responses of PP-,PS1-and PS2-waves.Within the 10° incidence angle,the PP-wave reflection coefficient difference between the HTI and isotropic media can be ignored.When the incidence angle is over the 10°,this difference in tight sandstones with different fracture density becomes more obvious and increases with the fracture density.At the 0° and 55° incidence angles,the PS-wave reflection coefficient of the HTI media is close to that of the isotropic media.The AVA-curve polarization reversals of the PP-,PS1-and PS2-waves are different at different fracture density.