【摘要】 孔隙度和含气饱和度是影响地震AVO响应的重要因素。采用AVO正演方法模拟不同储、盖层组合、不同孔隙度和含气饱和度时的地震反射,基于Zoeppritz方程的Shuey两参数近似式和Castagna砂岩分类方案,利用AVO截距和斜率属性的变化规律对储层含气性进行尝试性的定量分析。AVO正演模拟结果表明,含气砂岩顶面的AVO响应变化是孔隙度和含气饱和度的综合响应,且在孔隙度增大时以截距下降为主,在含气饱和度增大时以斜率下降为主;且当含气饱和度大于20%后,AVO响应变化减弱。当盖层阻抗低于储层骨架阻抗时,随孔隙度和含气饱和度的增大AVO响应类型由Ⅱ类过渡为Ⅲ类;当储、盖层骨架阻抗相当时,其类型由Ⅲ类过渡为Ⅳ类;当盖层阻抗高于储层骨架阻抗时,AVO响应主要为Ⅳ类。更多还原

【Abstract】 Porosity and gas saturation play a significant role on AVO responses.We use in this paper AVO forward modeling to create the seismic reflection for various assemblages of seal and reservoir with various porosity and gas saturation.Then we perform a quantitative analysis of gas saturation by the variations of AVO intercept and gradient derived from Shuey’s two-term approximation and Castagna’s classification.It is demonstrated that both sand porosity and its gas saturation impact on AVO responses:①AVO intercept decreases with porosity increasing,and gradient decreases with gas saturation increasing.②AVO response varies weakly while gas saturation is bigger than 20%.AVO responses of gas bearing sand transits from classⅡto classⅢ when the acoustic impedance of seal is lower than the reservoir matrix impedance,and from classⅢto classⅣ when the acoustic impedance of seal and the reservoir matrix impedance are equivalent,classⅣ occupies a dominant position when the acoustic impedance of seal is higher than the reservoir matrix impedance.更多还原