Midland Valley - the structural geology experts

Abstracts

Reducing Geological Uncertainty

through Structural Validation

G.Johnson, J.Grocott and A.Gibbs (all Midland Valley).

Oral Presentation accepted for Geological Disposal of Radioactive Waste: Underpinning Science andTechnology, 18 -20 October 2011, Loughborough University.

Abstract

Geological disposal of radioactive waste requires a sound and rigid understanding of the geology of the potential disposal site. To do so, requires the collection and collation of a wealth of geological data from surface outcrop data to subsurface well-logs and seismic surveys. However, uncertainty is intrinsic to nearly all forms of geological data (e.g. Davis, 2002, Mann, 1993). Uncertainty can be reduced by applying best practice approaches developed in the oil and gas and mining sectors to construct structurally valid 3D geological models for radioactive waste disposal sites. A structurally valid model is one which incorporates the kinematic history of the model to assess the dynamic development of the structure. A complete structural restoration incorporates line length and area balancing techniques, decompaction and reconstruction that establishes the (in)validity of the original interpretation.

We present data and exemplar workflows for a structural assessment of a geological disposal site. We show that the establishment of the structural geological history through restoration and balancing enables a greater assessment of the potential for containment through, for example, assessing fault networks. It also permits the subsequent development of a structurally grounded ‘fracture recipe’. This recipe contains various proxies for fracture generation based on forward modelled strains of the structure which when realised can be tested for stability in present day stress fields. This information can then be used to calculate block sizes as well as potential hydrodynamic pathways.

Keywords : 3d model building, 3d restoration, validation, uncertainty, decompaction, radioactive waste disposal