波形驱动下多参数约束高分辨率反演方法——以四川盆地渝西地区龙马溪组页岩气为例

基于叠后地震波形指示反演在薄储层预测方面的优势，以及叠前弹性参数较叠后弹性参数信息更丰富、对储层的敏感性更高的特点，根据岩石物理资料，应用地震驱动+储层构型约束的高精度叠前随机反演方法，探寻定量表征优质薄页岩的技术，以期为深层页岩气地质甜点预测提供技术支撑。首先，基于道集波形相似性、AVO特征和空间距离的三变量优选方法提取结构相似的井数据作为空间估值样本，然后建立待判别道集初始模型；其次，以统计的弹性阻抗作为先验信息，应用“基于叠前道集特征指示的马尔科夫链-蒙特卡洛随机模拟算法”进行叠前地震波形指示反演，最终得到高精度的叠前弹性参数反演成果。实际应用表明，应用所提方法有效预测了龙一段一亚段1-2小层优质页岩厚度，基于特征参数的井震高频模拟精确模拟了龙一段一亚段1-2小层地质甜点参数，为页岩气勘探提供了技术支撑。

Multi-parameter constrained high-resolution inversion method driven by waveform: A case study of Longmaxi Formation shale gas in western Chongqing,Sichuan Basin

The post-stack seismic waveform indication inversion shows advantages in thin reservoir prediction, and pre-stack elastic parameters have more information and are more sensitive to reservoirs than post-stack elastic parameters. Taking advantage of them, this paper applies the high-precision pre-stack stochastic inversion method under seismic drive and reservoir configuration constraint to quantitatively characterize high-quality thin shale reservoirs with petrophysical data in hope of providing technical support for the prediction of geological sweet spots of deep shale gas. Firstly, the three-variable optimization method based on gather waveform similarity, AVO feature and spatial distance is employed to extract wells with similar structures as spatial estimation samples, and then the initial model of the to-be-discriminated gather is established. Secondly, with the statistical elastic impedance as the prior information, the pre-stack seismic waveform indication inversion is performed with "Markov chain Monte Carlo stochastic simulation algorithm based on the pre-stack gather feature indication." Finally, a high-precision inversion result is obtained with pre-stack elastic parameters. The practical application demonstrates that this method effectively simulates the thickness of high-quality shale in 1-2 layer in the first sub-member of the first member of Longmaxi Formation, and accurately simulated the geological sweet spot parameter therein on the basis of the high-frequency well-seismic simulation of the characteristic parameters. This research provides technical support for shale gas exploration.