ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    可学习初始速度的全波形反演模型

    Full Waveform Inversion Model of Initial Velocity can be Learned

    • 摘要: 在地球物理油气勘探领域,地震波传播速度被视为判别地下介质的关键参数之一。全波形反演(Full Waveform Inversion,FWI)是一种流行的地球物理成像技术,其首先给定一个初始速度模型,通过迭代过程最小化速度模型生成的模拟地震记录与实际观测地震记录之间的偏差,从而学到高分辨率的地下速度模型。初始化准确的速度模型是实现全波形反演成像的先决条件,目前全波形反演强依赖于初始速度模型。当初始速度模型与真实模型存在较大差异时,理论波场与观测波场的匹配容易产生周期跳跃现象。笔者提出一种基于生成对抗网络的可学习初始速度的全波形反演模型(FWI with initial velocity learnable by neural network,FWI_IVLNN),其通过神经网络学习初始速度参数,融合随机速度生成速度模型,基于生成对抗思想反演速度模型,利用物理生成器生成模拟地震记录,通过判别器判别模拟记录和观测记录,通过无监督模式学习初始速度模型和网络参数。网络返回的梯度同时传给神经网络和物理生成器,借助梯度实现数据驱动和模型驱动的速度模型反演。定量和定性实验表明,FWI_IVLNN对初始速度模型依赖性较低,速度模型反演结果精度更高。

       

      Abstract: In the field of geophysical oil and gas exploration, the velocity of seismic wave is regarded as one of the key parameters to distinguish underground media. Full Waveform Inversion (FWI) is a popular geophysical imaging technique in which a high-resolution subsurface velocity model is learned by first giving an initial velocity model and then minimizing the deviation between the simulated seismic record generated by the velocity model and the actual observed seismic record through an iterative process. The initialization of accurate velocity model is a prerequisite for the realization of full waveform inversion imaging, which is strongly dependent on the initial velocity model. When there is a big difference between the initial velocity model and the real model, the matching between the theoretical wave field and the observed wave field is easy to produce the phenomenon of period hopping. This paper proposes a full-waveform inversion model (FWI with initial velocity learnable by neural network, FWI_IVLNN)based on generative adversarial networks that can learn initial velocity parameters. It learns initial velocity parameters through neural networks and integrates stochastic velocity to generate velocity models. Based on generative adversarial idea, the velocity model is inversion, the simulated seismic record is generated by physics generator, the simulated record and the observation record are discriminated by discriminator, and the initial velocity model and network parameters are learned by unsupervised mode. The gradient returned by the network is transmitted to both the neural network and the physical generator, and the data-driven and model-driven velocity model inversion is realized with the help of the gradient. Quantitative and qualitative experiments show that FWI_IVLNN is less dependent on the initial velocity model, and the accuracy of velocity model inversion is higher.

       

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