Accelerating Seismic Modelling and Inversion by Exploiting Wavefield Smoothness

地震成像是油气上游市场的核心。鉴于采集数据集的激增，活动超过数十万次，波通过复杂介质传播的相应建模提出了一个巨大的计算挑战。在过去，2D采集和2D建模代表了一种常见的近似，与3D方法相比，它将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（如盐下）本质上是3D的，因此2D近似的有效性是值得怀疑的。我们提出了一种新的方法，该方法以二维方法为代价，在三维域中传播波。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。这将包括重写网格部分，并添加吸收边界，而大部分方法将保持不变。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SEG/EAGE盐和逆冲模型等合成数据。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，因此可以实现快速成像。这项工作的第二个组成部分将把新方法结合到真正的3D建模的混合方法。这种方法将基于“精确边界条件”，苏黎世联邦理工学院的Johan Robertsson教授和他的同事最近已经证明了这种方法非常有效。轴对称和混合建模的联合框架是地震建模、成像和反演等领域普遍关注的问题。这个项目属于“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.