Airborne Gravity 2010 - Geoscience Australia

Airborne Gravity 2010
triangulated polyhedrons. Interoperability with widely used commercial software such as GOCAD,
GeoModeller (Intrepid), Oasis Montaj (Geosoft), and GMSys (Geosoft) is a key feature of IGMAS+.
Lahmeyer et al. (2010) illustrate this point by describing a modelling workflow that is used at Statoil.
Users construct realistic geological models using interactive model editing tools. Inversion of
geophysical data is carried out in the 3D geological model environment to obtain various model
parameters (e.g., geometry, density, susceptibility, and magnetization). The geological foundations of
IGMAS+ are important since geological constraints play a critical role in the minimisation of the
ambiguities that are inherent in gravity and magnetic modelling.
When a geometry change is made using the modelling interface, the user can update the gravity effect
(and/or the tensor components) of a model very quickly because it is only that part of the response
that is related to the changed triangles that needs to be re-calculated. Optimized storage structures
enable density inversion to be performed very rapidly.
Changes to the geometry of a model can only be made on a set of predefined parallel vertical sections
(Figure 1 and Figure 2). This is a relatively small restriction that makes geometry change easy, and
avoids the need for a complex 3D editor. The measured and calculated gravity fields can be displayed
together with the vertical sections (Error! Reference source not found.). After each geometry
change, the gravity can be recalculated. Since the structures of a model are triangular, IGMAS+ can
handle complex geological features such as overhangs of salt domes (Figure 2). It has been noted
that the software could benefit from a greater degree of integration with seismic interpretation systems.
Figure 1. IGMAS+ model structure. Seismic sections are not part of the model structure but can
easily be imported as images.
IGMAS+ provides multiple fully linked graphical windows that allow geoscientists to comprehend 3D
geological structures and the available geophysical data sets. The aim of the design was always to
allow the geoscientist to be in the driver’s seat and to make it as easy as possible to construct
complex geological models.
The current development of IGMAS+ software is focussed on:
� improving the user interface and model editing functionality,
� programming of an undo function,
� an option to perform modelling in a spherical coordinate system,
� interfaces to other tools like GOCAD, Geosoft and GeoModeller,
� basic functionality for filtering and analysis, and
� allowing more complex density functions to be assigned to the currently homogeneous bodies.
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