煤层气AVO反演对地震资料偏移距的要求研究

Research on requirement for offset of seismic data about coalbed methane AVO Inversion

为了研究AVO反演在煤层气勘探中对地震资料偏移距的要求,以正演模拟为研究手段,根据钻井、测井数据和地震勘探解释成果,建立了普遍适用的煤层气储层地质模型,应用Zoeppritz方程组弹性模量近似式,计算出其各项系数对入射角的梯度。理论模型的正演模拟表明,将AVO反演应用于煤层气勘探时,地震资料的最大偏移距应当保证最大入射角接近或等于反射系数对入射角梯度极值对应的入射角。通过对实际钻井资料进行AVO模拟,结果表明在煤层气勘探中应用AVO反演,地震资料的最大偏移距只要接近、等于或略大于目的层深度,就可以反映振幅随偏移距变化的特征,足以满足煤层气勘探中AVO反演对地震资料偏移距的要求。

In order to study the requirement of the AVO Inversion to the offset distance of the seismic information from the coalbed methane exploration,with the forward simulation as the study means,according to the drilling and logging data and the seismic exploration explained achievements,a general appropriate geological model of the coal bed methane reservoir was established and with the elastic modulus approximate formula of the Zoeppritz Equations applied,the incident angle gradient of each coefficient was calculated. The forward simulation of the theoretical model showed that when the AVO Inversion was applied to the coal bed methane exploration,a max offset distance of the seismic information should ensure the max refraction average angle close to or equal to the refraction average angle relevant to the refraction average angle gradient of the reflection coefficient. With the actual drilling information applied to conduct the AVO Simulation,the results showed that the AVO Inversion applied to the coal bed methane exploration,when the max offset distance of the seismic information close to,equal to or little higher than the target stratum depth could reflect the features of the amplitude with the offset varied and could fully meet the requirements of the AVO Inversion to the offset distance of the seismic information from the coalbed methane exploration.