Accelerating Seismic Modelling and Inversion by Exploiting Wavefield Smoothness

地震成像是碳氢化合物上游市场的核心。鉴于采集数据集的激增，运动超过数十万次射击，通过复杂介质的波传播的相应建模提出了一个艰巨的计算挑战。在过去，2D采集和2D建模代表了一种常见的近似方法，与3D方法相比，其计算成本降低了几个数量级。如今，大多数运动和结构的复杂性（例如盐下）本质上是3D的，使得2D近似的有效性是值得怀疑的。我们提出了一种新的方法，它在3D域中传播波，但以2D方法为代价。这是通过轴对称（2.5D介质）的多极展开来实现的。Tarje Nissen-Meyer的相应代码在全球地震学中得到了很好的建立;本项目旨在将该方法应用于局部尺度。这将包括重写部分网格，并添加吸收边界，而该方法的大部分内容将保持不变。我们将针对参考解决方案广泛测试这种新方法，并将其应用于合成数据，如SEG/EAGE盐和逆掩模型。与地震行业的关系也存在，因此我们最终将根据实际数据验证它。该代码比3D建模便宜几个数量级，因此将允许快速成像。这项工作的第二个组成部分将把新方法与混合方法中的真正3D建模联系起来。这种方法将基于“精确边界条件”，最近已经被苏黎世联邦理工学院的Johan Robertsson教授和同事证明是非常有效的。轴对称和混合建模的联合框架将引起地震建模、成像和反演等一般领域的广泛兴趣，该项目福尔斯“地球资源”研究领域。

Seismic imaging is at the core of the hydrocarbon upstream market. Given a surge in acquisition datasets with campaigns exceeding hundreds of thousands of shots, the corresponding modelling of wave propagation through complex media poses a formidable computational challenge. In the past, 2D acquisitions and 2D modelling represented a common approximation which decreased the computational cost by orders of magnitude compared to 3D methods. Nowadays, most campaigns and the complexity of structures (e.g. subsalt) are inherently 3D such that the validity of the 2D approximation is questionable. We propose a new method, which propagates waves in a 3D domain, but at the cost of a 2D method. This is achieved by a multipole expansion for axisymmetric (2.5D media). A corresponding code by Tarje Nissen-Meyer is well established in global seismology; this project aims at applying the method for local scales. This will include rewriting parts of the meshing, and adding absorbing boundaries, whereas the bulk of the method will remain unchanged. We will extensively test this new approach against reference solutions, and apply it to synthetic data such as the SEG/EAGE salt and overthrust models. Relations to the seismic industry exist as well, such that we shall eventually validate it against actual data. The code is orders of magnitudes cheaper than 3D modelling, and thus will allow for rapid imaging. A second component of this work will tie the new methodology to true 3D modelling in a hybrid approach. This approach will be based on "exact boundary conditions", which have recently been shown to work excellently by Prof. Johan Robertsson and co-workers at ETH Zurich. The joint framework of axisymmetric and hybrid modelling shall be of wide interest to the general fields of seismic modelling, imaging and inversion.This project falls within the "Earth resources" research area.