Model development and validation of results

Our problem: How to connect complex heterogenous facies model to geophysical data?

Airborne geophysical data are widely used in geological and hydrogeological simulations, because these extensive multi-parameter data sets can complete the limited data base of the user models. However, the missing direct coupling of geophysical and user models complicates the effective interpretation and use of airborne geophysical data. The integration of geophysical, sedimentological, petrophysical data and facies models is a well-established method in the hydrocarbon exploration, but has been applied to aquifer systems only in the last years. In particular, there is a lack of inexpensive and modern concepts for the 3D interpretation and visualisation of depositional systems and groundwater-flow. Therefore, hydrogeological simulations are mainly based on very simple facies models, which do not reflect the complex system reality and therefore often lead to wrong results. Especially in sensitive coastal regions and individual hydrogeological settings, a detailed knowledge of saltwater distribution and dynamics is important.

The architecture of sedimentary bodies determines the heterogeneity of many reservoirs and controls the spatial distribution of hydraulic properties. Various scales of heterogeneities are distinguished, including lithofacies (cm to some m), architectural elements (1 to some 10 m) and larger-scale lateral and vertical stacking patterns of depositional systems (10 to some 100 m). Tectonic processes lead to the formation of compartments, which are bounded by faults. Such faults can be impermeable for fluids. Both, formation of compartments and faulting create a very heterogeneous subsurface geometry. This affects the fluid-flow, as well as the distribution of the effective geophysical parameters. The ambiguity of geological, hydrogeological and geophysical data may lead to the reconstruction of different subsurface models and therefore implicate different exploration strategies.
The aim of this sub-project is to iteratively connect the heterogeneity distribution within synthetic subsurface models to airborne geophysical data and to test and evaluate the plausibility of these models.

Stairstepped Gocad® model of a subglacial tunnel valley Source: Dipl.-Geow. D. Steinmetz, Institut für Geologie, Leibniz Universität Hannover

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Our solution: Develop new interfaces and visualisation tools for modelling and evaluation!

Two semi-synthetic 3D subsurface Gocad® models will be generated. Pre-existing geophysical data sets of the BGR and of partner sub-projects will be selected as input for the inversions and simulations. Subsequently the geological subsurface models will be adjusted and compared with the results of the inversions and simulations, so that new algorithms can be tested. In addition, we can implement complex tectonic structures, such as fault zones, which will have a strong impact on the modelling workflow. In a second step, initial conditions and boundary conditions for inversion and modelling (a-priori-parameter) and their controlling factors for the results (a-posteriori-parameter) will be tested. To exchange results and to enable their common and uniform comparison, we will extend IGMAS+ towards a high-end software for the 3D visualisation. Therefore interfaces between IGMAS+ and Gocad® and/or other user software in the AIDA project will be developed and implemented. In addition, we aim to provide tools and knowledge for data-exchange for the other subprojects. The different modelling results of the AIDA-subprojects will be validated, compared and visualized on a low-cost-VR-installation.

Regular density-grid of the subglacial tunnel valley represented by using OpenSceneGraph. The stairstepped Gocad® model of the tunnel valley is used as constrain for gravity-modelling within IGMAS+ Source: Dipl.-Geoinf. P. Menzel, Christian-Albrechts-Universität zu Kiel

The modelling results of the different subprojects base on very heterogeneous modelling-software and -philosophies. The aim of SP 5 at CAU Kiel is to harmonize the results for comparison, validation and synoptic visualisation.
To ensure the comparability for validation of the heterogeneous modelling-results there will be applied various general quality-measurements for model-geometry and model-parameterisation. For synoptic 3D stereo-visualisation the modelling-results will be represented in a general way into the modelling-software-independent open-source-visualisation-system OpenSceneGraph. This visualisation-software will be used for interactive presentation, analysis and validation of the AIDA-results.