WinGLink® Marine is a dedicated software package for QC, analysis and interpretation of marine MT and CSEM data.
The program handles the following survey data:
- Marine CSEM (Controlled source EM, frequency and time domains)
- Marine Magnetotellurics (MMT)
WinGLink® Marine allows the user to integrate marine MT and CSEM data with seismic and gravity data. Information from vertical or deviated wells can be posted on maps or cross-sections to add model constraints.

Display of time series; extraction and archival of time-limited segments; filtering and de-spiking; computation of spectra, spectrograms, and cross-correlation.

Left: example of time series. Right: spectrogram.

This module handles editing and display of MT and CSEM data, imported from EDI files (MT) and from ASCII or Excel files (CSEM). MT data can be decomposed in a variety of ways, static stripped or shifted. For all techniques, bad data can be masked and curves can be completely or partially shifted. CSEM data can be normalized to a specified background response or to a specific station.

MT: a dialog window allows interactive editing of MT modes, static shifts and station status for each sounding of a profile. Unwanted data can be masked separately for TE and TM modes and tipper. The edited curves are fed directly into the 2D inversion program.
CSEM: Pseudo-sections of amplitude, phase, normalized amplitude, phase difference are plotted in pseudo-depht v. distance space. In-, out-, or both tow directions can be selected, radial or azimuthal modes, etc.


Left: Normalised amplitude, 0,25 Hz, 3D reservoir - Phase difference, 0,25 Hz, 3D reservoir.
Right: 1D marine TEM step-on and impulse responses.

Survey stations, including deviated wells and other relevant reference points are entered using the MAPS module. This is also used to extract and grid both observed parameters (e.g. MT apparent resistivity at 0.01 Hz or CSEM phase at 5000m offset) and also interpreted ones (e.g. resistivity from 1D inversion at 2000m bsl) for display as line and color filled contour maps. Profile traces added to the area are used to construct sections. This is done by adding to each profile a set of stations selected from the database. The corresponding data are used to generate pseudo-sections or distance/depth cross-sections.

In controlled-source mode, forward models can be computed for a variety of field components, field data can be inverted jointly (including MT, E and orthogonal H) or singly. In frequency domain, the "air wave" can be computed, and an approximate correction can be applied for shallow water conditions. This module is ideal for pre-survey sensitivity studies, and for first-pass interpretation.

The 2D Inversion module is used to perform smooth and sharp-boundary inversions of marine MT data, using exact finite difference algorithms. It provides a user-friendly interface for creating and editing 2D meshes and allows the user detailed control over the inversion parameters. To assist in the interpretation of the modeled data, the module includes options for outputting sensitivity maps, creating pseudo-sections and comparison of observed and computed responses.

This module is based on Geosystem's finite-difference 3D codes, and is supported by a powerful graphical interface to edit the 3D mesh and to transform the results into EDI impedances (MT), amplitude and phase (frequency-domain CSEM) or amplitude (TEM). It is presently implemented for marine MT and frequency-domain CSEM, and will shortly be available also for marine TEM. Forward computation times are about an hour on a conventional PC for a 100 x 100 x 100 element mesh for six frequencies for the MT case or for twelve transmitter positions (marine CSEM). 3D inversion is offered as a service by Geosystem, and results are readily imported into WinGlink® Marine.



Left: 3D fCSEM model.
Right: Computed responses (amplitude and phase) for a site at the edge of the resistive target, compared with 1D responses.

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