Technology
Processing and modelling
Advanced processing and modelling are integral parts of successful seabed-logging surveys.
Every EMGS seabed-logging survey starts with a feasibility study that uses in-house algorithms to predict whether a given target will yield measurable responses. Our modelling tools also enable us to plan and optimise surveys, and are used extensively during interpretation.
Basic processing is performed offshore after data have been quality controlled. Advanced processing, such as up and down separation for shallow and variable water-depth surveys, is performed in our Trondheim processing centre, Norway. We also offer a specially designed package to handle azimuthal data, which is acquired to increase data coverage.
Depth migration and inversion, which require massive computing power, can be performed to give the location and depth of resistivity anomalies.
Main Features
- In-house plane-layer modelling software. Plane-layer modelling provides a quick indication of the expected seabed-logging response. The horizontal and vertical components of the electric and magnetic fields are calculated, and the models can include subsurface anisotropy.
- Powerful in-house 3D modelling. 3D forward modelling is a finite-difference time-domain code, which includes water-air interaction. The perfectly matched layers method is used to avoid artificial reflections. Any receiver-source pattern can be extracted from the 3D modelling results, which makes the modelling tool important for survey design and interpretation.
- Up-down separation for shallow-water surveys. By measuring and processing magnetic and electric field components, EMGS can distinguish energy that has travelled along the water-air interface (the airwave) from subsurface energy. These processes mean surveys conducted in shallow water can be processed successfully.
- Processing power. Solving 3D Maxwell equations to process 2D lines and migrate and invert 3D data requires formidable processing power. EMGS operates a Dell Blade cluster computer with 1060 processors operating at 7.2 terra FLOPS.
- Depth migration and inversion. 2D and 3D images of resistive bodies can be created from seabed-logging data using our proprietary depth-migration method. The resulting depth-migrated images can be used to make geo-models, which constrain an inversion process that gives a final resistivity model.
