【摘要】 地层Q值是用于油气检测的重要参数,针对应用叠后地震资料求取Q值存在多解性的问题,探索了基于叠前道集求取Q值的QVO(地震品质因子Q随偏移距变化)方法,进行了数值模型试算和实际地震资料的应用,结果证明了QVO方法的正确性和有效性。该方法首先利用小波变换将经过动校正处理的CMP道集进行时频域转换,通过选择不同的时窗和与之相对应的尺度因子,利用小波域谱比法计算非零偏移距频谱比斜率值;然后根据频谱比斜率值随偏移距的变化关系,求得零偏移距处的Q值。模型试算提取的频谱比斜率与偏移距平方近似呈线性关系,与理论吻合,证实了理论的正确性。将QVO方法应用于实际工区地震资料提取地层Q值,结果表明,含气区与非含气区的Q值差异明显,含气区的Q值较低,表现为强吸收。与叠后地震资料提取的Q值相比,QVO方法提取的Q值精度高,更能真实地反映地层吸收特征,提高了储层含气性检测的精度。更多还原

【Abstract】 The Q value of formation is an important parameter of oil and gas detection.According to the ambiguity for Q computation by post-stack seismic data,we discussed the Q versus offset(QVO) method which extracts Q value through pre-stack gathers.Firstly, the CMP gathers after DMO were carried out time-frequency transform; by selecting different time window and corresponding scale factors,the slope of non-zero offset spectral ratio was calculated by spectral ratio method in wavelet domain.Then,in terms of the variation relationship between slope and offset,we calculated the Q value of zero offset.By model testing,we discovered that the extracted curve of slope and offset square is approximate linear,which is coinciding with the theory and proves the correction of the theory.In addition,the QVO method was used to extract Q of actual formation, and the result shows that the difference of Q between gasbearing area and non-gas area is obvious.In gas-bearing area,the Q is relatively low,which displays strong absorption.The precision of Q computed by QVO method is higher that from post-stack seismic data,which can reflect the actual absorption of the formations and improve the accuracy of gas prediction.更多还原