What is PETGEM?

Electromagnetic methods (EM) are an established tool in geophysics, with application in many areas such as hydrocarbon and mineral exploration, reservoir monitoring, CO2 storage characterization, geothermal reservoir imaging and many others. In particular, the marine Controlled-Source ElectroMagnetic method (CSEM) has become an important technique for reducing ambiguities in data interpretation for hydrocarbon exploration. In order to be able to predict the EM signature of a given geological structure, modelling tools provide us with synthetic results which we can then compare to real data. In particular, if the geology is structurally complex, one might need to use methods able to cope with such complexity in a natural way by means of, e.g., an unstructured mesh representing its geometry. Among the modelling methods for EM based upon 3D unstructured meshes, the Nédélec Finite Elements (FE), a type of Edge Elements, offer a good trade-off between accuracy and number of degrees of freedom, i.e. size of the problem.

In the multi-core and many-core era, parallelization is a crucial issue. Nédélec FE offer good scalability potential. Its low DOF number after primary/secondary field decomposition make them potentially fast, which is crucial in the future goal of solving inverse problems which might involve over 100,000 realizations. However, the state of the art shows a relative scarcity of robust edge-based codes to simulate these problems.

On top of that, Parallel Edge-based Tool for Geophysical Electromagnetic Modelling (PETGEM) is a Python tool for the scalable solution of EM on tetrahedral meshes, as these are the easiest to scale-up to very large domains or arbitrary shape. It supports distributed-memory paralelism through mpi4py and petsc4py packages.

As a result, PETGEM tool allow users to specify edge-based variational forms of H(curl) for the simulation of electromagnetic fields in real CSEM surveys with high accuracy, reliability and efficiency.

PETGEM code is developed as open-source at Computer Applications in Science & Engineering (CASE) of the Barcelona Supercomputing Center (BSC). Requests and contributions are welcome.