地下储层含烃类流体引起地震信号频率的衰减,目前对叠后地震资料的频率衰减研究较多,但是涉及叠前道集上的频率衰减研究较少。作者综合叠前AVO的计算公式及频率衰减积分计算式,对叠前部分叠加角道集的频率衰减梯度差值(Frequency Attenuation Gradient vs.Offset,简称FAGVO)的计算公式进行了推导,显示完全弹性介质的FAGVO为零,粘弹性介质的FAGVO为负值,且FAGVO的绝对值大小与介质粘度、频率变化、反射系数及高频的衰减有关。FAGVO可以消除部分影响地下岩层频率变化因素的干扰,从而突出含烃储层频率衰减梯度的异常,达到利用叠前部分叠加道集进行含烃类流体检测的目的。该方法经过二维波动方程正演模型的验证,检测效果理想,且该方法对钻井信息的依赖较小,可应用于油气地震勘探阶段,尤其是无井区的勘探,既经济又高效。 Hydrocarbon fluids in underground reservoirs cause the attenuation of seismic signal frequency. At present, there are many researches on the frequency attenuation of post-stack seismic data, but there are few researches on the frequency attenuation of prestack gathers. Based on the calculation formula of prestack AVO and the formula of frequency decay integral, the author deduces the formula of Frequency Attenuation Gradient vs. Offset (FAGVO), which shows that the complete elastic medium Of FAGVO is zero, FAGVO of viscoelastic medium is negative, and the absolute value of FAGVO is related to medium viscosity, frequency change, reflection coefficient and attenuation of high frequency. FAGVO can eliminate some interferences that affect the frequency variation of underground strata, so as to highlight the abnormal frequency attenuation gradient of hydrocarbon reservoirs and achieve the purpose of detecting hydrocarbon-bearing fluids by using prestack superimposed gathers. The method is validated by two-dimensional forward modeling of wave equation, and the detection result is satisfactory. The method is less dependent on drilling information and can be applied to oil and gas exploration, especially exploration without oil well, which is economical and efficient.