Methodology for iterative and integrative geomodelling in a multidisciplinary workspace

Category Other
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Munier, Raymond
Holding Date 04 October 2008

The safe disposal of radioactive wastes imposes a formidable challenge and requires expertise from a broad range of scientific disciplines. The application for the construction of a repository requires a site description within which the geological model, i.e. the interpreted geometries and properties of relevant components of the geosphere, constitutes a cornerstone. As two sites are currently being investigated in Sweden, the methodology for geoscientific modelling needs to be predominantly site-neutral to ensure means of adequate comparison of the sites.
A vital component of the modelling process is to establish a consensus among the geoscientific disciplines within the modelling project regarding terminology. The process of data gathering by different methods (e.g. airborne or ground geophysics), the method-specific interpretations (e.g. lineament model) and the modelling (e.g. co-interpretation of topographic and geophysical data) needs to be formalised such that each activity is self-contained regarding quality assurance, analysis and reporting. In essence, this means breaking the analysis process into small, independent activities, the outcomes of which are collected and modelled in batches.
The geological modelling is initiated by the construction of models of various dimensions. Each borehole is first interpreted independently (single hole interpretation, SHI), using the outcome of integrated interpretation of various independent methods, producing 1-D geological maps. Similarly, interpretation of geophysical data yields various 2-D lineament maps whereas the geological outcrop mapping and sampling yields 2-D outcrops maps.
The integrative modelling is the process in which lineament- and outcrop maps are ennobled to form deformation zone- and lithological maps respectively. The resulting integrated product is a 2D bedrock geological model. This process endorses multiple lines of evidence for the interpretation and aids to assess uncertainty issues and level of confidence. The 3-D modelling process consists of collecting all 1-D and 2-D models into a 3-D container for cross-hole and surface-hole modelling, yielding the ultimate outcome; a 3-D geological model which forms the geometrical framework for all geoscientific disciplines in the project. A formalised feedback process from neighbouring disciplines is essential to ensure inter-disciplinary consistency in the resulting site description. For this purpose, we have found it fruitful to make use of domains, (e.g. lithological domains, hydraulic domains, etc) to endorse integration. The process of domaining is the purpose driven subdivision of the model volume into internally homogeneous sub volumes with respect to a specific collage of properties.