基于地震数据子集的波形反演思路、方法与应用

地震数据与地下介质物性参数之间的复杂关系,决定了地震全波形反演在理论方法上面临着强烈的非线性难题.地下不同物性参数的不同分量在地震数据上具有不同的表现,勘探的不同阶段对地下介质模型的精度也具有不同的要求,这就决定了在地震全波形反演过程中不必时刻追求地震数据全部信息的匹配,部分信息的匹配就有可能解决现阶段的某些问题,还可以一定程度上规避匹配全部地震信息所遇到的强烈非线性难题.基于这样的考虑,我们提出了利用地震数据子集进行波形反演的思路,给出了统一的反演方法,并通过基于包络数据子集以及反射波数据子集的波形反演的理论模型与实际资料反演试验,证明了所提出的波形反演思路和方法的正确性.

Strategy and application of waveform inversion based on seismic data subset

The main difficulty in seismic full waveform inversion (FWI) is the strong nonlinearity, which is caused by the complexity of seismic wave propagation. Different components of elastic parameters result in different characteristics of seismic data. Meanwhile, different inversion accuracy is required in different stages of exploration or exploitation. So, it is really not necessary to pursue matching all the seismic information during the inversion. Some problems can be solved by matching part of seismic information and the strong nonlinearity can also be alleviated by this way. According to this consideration, a generalized FWI strategy and method based on seismic data subsets is presented. For different seismic data subsets, the gradients of the misfits have the same form and can be calculated by two modeling applications just as traditional FWI, and the only difference in calculating the gradients is the adjoint sources. During the waveform inversion based on seismic data subsets, the responses of seismic data to different scales of perturbation on different media parameters should be analyzed intensively. Different seismic data subsets should be used in different stages of full waveform inversion. And then the residual of this seismic data subset is back-projected along the reasonable sub-kernels to decide where and which component of the medium parameter need to be updated. As examples, envelope and reflection data subsets are used in FWI with synthetic and real data to prove the validity and effectiveness of our presented FWI strategy and method. Especially, in the absence of low frequency contents, reasonable misfits can be used to recover the background compressional and shear velocity using these FWI methods.