基于频变AVO反演的页岩储层含气性地震识别技术

结合地震岩石物理技术，研究了叠前频变AVO反演在四川盆地龙马溪组页岩储层含气性识别中的应用.首先，应用Backus平均理论将测井数据粗化为地震尺度储层模型，应用传播矩阵理论进行高精度地震正演及井震标定，分析页岩气储层地震响应特征.其次，基于岩心观测结果，应用Chapman多尺度裂缝理论设计页岩气储层理论模型，研究储层衰减、频散以及对应的地震反射特征.应用该理论模型测试频变AVO反演方法，计算结果表明：对于研究区地层结构和地震数据，区分流体类型的优势频率不是地震子波的主频，还受层间调谐干涉等储层结构因素控制，也进一步说明理论模型测试和标定的重要性.最后，将频变AVO反演技术应用到四川盆地龙马溪组页岩地层，计算得到的频散属性为页岩气储层含气性识别提供依据.

Gas identification of shale reservoirs based on frequency-dependent AVO inversion of seismic data

Combining with seismic rock physics, we study the application of pre-stack frequency-dependent AVO inversion to gas identification of shale in the Longmaxi Formation, Sichuan Basin. First, we upscale the well data to seismic scale to obtain a reservoir model based on Backus average theory, and then conduct seismic modeling using the propagator matrix method followed by seismic-well tie for the analysis of seismic signatures from the shale gas reservoir. Then, based on core observations, we use the multi-scale fracture theory to design a theoretical model of shale gas reservoirs. Also, we calculate velocity dispersion and attenuation and the corresponding seismic reflections for the model. Afterwards, the frequency-dependent AVO inversion method is tested using the theoretical model. Calculation results show that for the target gas reservoir with a specific stratigraphic structure, the optimum frequency for fluid identification is not necessarily consistent with the dominant frequency of incidence seismic wavelets. The optimum frequency is influenced by tuning, interference and propagation effects. It illustrates the importance of the study on the theoretical model. Finally, we apply the frequency-dependent AVO inversion to the shale in the Longmaxi Formation of Sichuan Basin. The calculated dispersion attributes provide evidence for gas identification in shale reservoirs.