论文部分内容阅读
介质各向异性是影响振幅随炮检距变化（AVO）的重要因素之一。本文将Aki和Rrchards的方法进行推广，推导出两个弹性横向各向同性（TI）介质密接条件下平面波反射和透射系数，并给出弱弹性TI假设下的近似式。近似式的物理意义明确，而且精度明显高于前人的结果。P－P波近似式表明，上下层的Thomsen各向异性参数差在小到中等入射角范围内对AVO起重要作用；而对更大的入射角（20以外），P波各向异性参数p差对AVO也有强烈的影响。就P－P波AVO拟合而言，TI不影响零炮校距反射系数，但对梯度有直接影响。对三类（高阻抗、近零阻抗差、低阻抗）各向同性的含气砂岩，研究了上覆TI页岩对P－P波AVO的影响，并指出上覆TI页岩可能会使含水砂岩呈较强的AVO增加趋势。
Media anisotropy is one of the important factors that influence the amplitude variation with offset (AVO). In this paper, we generalize the method of Aki and Rrchards to deduce the reflection and transmission coefficients of plane waves under two elastic transverse isotropic (TI) media, and give the approximate formula under the assumption of weak elastic TI. The approximate physical meaning is clear, and the accuracy is significantly higher than the previous results. The P-P wave approximation shows that the Thomsen anisotropy parameter difference between the upper and lower layers plays an important role in the AVO at small to medium angles of incidence. For larger angles of incidence (beyond 20), P-wave anisotropy parameters p Poor also has a strong impact on AVO. In terms of P-P wave AVO fitting, TI does not affect the zero shot gamut reflection coefficient but has a direct effect on the gradient. The effects of overlying TI shale on P-P AVO are studied for three types of isotropic (high impedance, near-zero impedance, low impedance) gas-bearing sandstones and it is pointed out that overlying TI shale may cause water-bearing Sandstone showed a strong trend of AVO.