Modelling geothermal reservoirs is challenging due to the large domain and wide range of length- and time-scales of interest. Attempting to represent all scales using a fixed computational mesh can be very computationally expensive. Application of dynamic mesh optimisation in other fields of computational fluid dynamics has revolutionised the accuracy and cost of numerical simulations. Here we present a new approach for modelling geothermal reservoirs based on unstructured meshes with dynamic mesh optimisation. The resolution of the mesh varies during a simulation, to minimize an error metric for solution fields of interest such as temperature and pressure. Efficient application of dynamic mesh optimisation in complex subsurface reservoirs requires a new approach to represent geologic heterogeneity and we use parametric spline surfaces to represent key geological features such as faults and lithology boundaries. The resulting 3D surface-based models are mesh free; a mesh is created only when required for numerical computations. Dynamic mesh optimisation preserves the surfaces and hence geologic heterogeneity. The governing equations are discretised using a double control volume finite element method that ensures heat and mass are conserved and provides robust solutions on distorted meshes. We apply the new method to a series of test cases that model sedimentary geothermal reservoirs. We demonstrate that dynamic mesh optimisation yields significant performance gains, reducing run times by up to 8 times whilst capturing flow and heat transport with the same accuracy as fixed meshes.

地热储层的建模具有挑战性，因为它涉及的领域很大，而且所涉及的时标和时标范围很广。尝试使用固定的计算网格来表示所有比例可能会非常昂贵。动态网格优化在计算流体动力学的其他领域中的应用彻底改变了数值模拟的准确性和成本。在这里，我们提出了一种基于非结构化网格和动态网格优化的地热储层建模新方法。在模拟过程中，网格的分辨率会发生变化，以最大程度地减少针对感兴趣的溶液场（例如温度和压力）的误差度量。动态网格优化在复杂地下油藏中的有效应用需要一种表示地质异质性的新方法，并且我们使用参数样条曲面来表示关键的地质特征，例如断层和岩性边界。生成的基于3D曲面的模型无网格；仅在需要进行数值计算时才创建网格。动态网格优化可保留曲面，从而保留地质异质性。控制方程使用双控制体积有限元方法离散化，该方法可确保热量和质量得以保留，并在变形的网格上提供鲁棒的解决方案。我们将该新方法应用于一系列模拟沉积地热储层的测试案例。我们证明了动态网格优化可以显着提高性能，