Repeated seismic surveys contain valuable information regarding time-lapse (4D) changes in the subsurface. Full-waveform inversion (FWI) of seismic data can provide high-resolution estimates of 4D change. We have adopted a new time-domain 2D acoustic time-lapse FWI method based on the central-difference scheme with higher order mathematical accuracy and reasonable computational cost. The method is rigorously tested on the SEG Advanced Modeling 4D time-lapse model and ocean-bottom-node data set. High-resolution 4D velocity estimates are obtained, which show strong (approximately 25%) velocity increases in a 75 m thick gas layer, as well as weaker (5%) changes due to geomechanical effects, the latter of which are poorly recovered by the conventional parallel 4D FWI method. We also perform the bootstrap 4D FWI method, and the result is contaminated by strong artifacts in the underburden, whereas the proposed central-difference method has fewer underburden artifacts allowing more reliable interpretations. In this realistic case study, acoustic FWI erroneously overfits some of the elastic scattered waves, and it cannot fit the strong elastic 4D coda waves well. The results show that the proposed central-difference 4D FWI method within the acoustic approximation may be a practical solution for time-lapse seismic velocity inversion.

中文翻译：

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中心差时移4D地震全波形反演

重复的地震勘探包含有关地下时移（4D）变化的有价值的信息。地震数据的全波形反演（FWI）可以提供4D变化的高分辨率估计。我们基于中心差分方案采用了一种新的时域二维声学时移FWI方法，具有较高的数学精度和合理的计算成本。该方法已在SEG Advanced Modeling 4D时移模型和海底节点数据集上经过严格测试。获得了高分辨率的4D速度估计值，该估计值显示了75 m厚的气体层中的速度有很强的（大约25％）增加，以及由于地质力学作用而导致的较弱的改变（5％），而后者却很难恢复。传统的并行4D FWI方法。我们还执行了引导4D FWI方法，并且结果被下伏地层中的强烈伪影所污染，而所提出的中心差分方法具有更少的下沉地物伪影，从而可以进行更可靠的解释。在这个现实的案例研究中，声学FWI错误地使某些弹性散射波过拟合，并且不能很好地适应强弹性4D尾波。结果表明，所提出的声场近似中的中心差分4D FWI方法可能是时移地震速度反演的一种实用解决方案。