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- ISSN: 2202-0586
- E-ISSN:
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oa Geological uncertainty and geophysical misfit: How wrong can we be?
- Australian Society of Exploration Geophysicists
- Source: ASEG Extended Abstracts, Volume 2013, Issue ASEG2013 - 23rd Geophysical Conference, Dec 2013, p. 1 - 5
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- 01 Dec 2013
Abstract
Geophysical inversion employs numerical methods to minimise the misfit between three-dimensional petrophysical distributions and geophysical datasets. Inversion techniques rely on many subjective inputs to provide a solution to a non-unique problem, including use of an a priori input model or model elements (a contiguous volume of the same litho-stratigraphic package) and inversion constraints. Inversions may produce a result that perfectly matches the observed geophysical data but still misrepresents the geological system. A workflow is presented that offers multiple starting models to inversion: (1) simulations are performed to create a model suite containing a collection of geologically possible models; (2) uncertainty analysis is then performed using stratigraphic variability to identify low certainty model regions and elements; (3) ‘Geodiversity’ analysis is then conducted to determine the geometrical and geophysical extremes within the model space; (4) geodiversity metrics are then simultaneously analysed using principal component analysis to determine which models exhibit common or diverse geological and geophysical characteristics, enabling the selection of models that are subjected to geophysical inversion.
The Ashanti Greenstone Belt, southwestern Ghana in west Africa is used as a case study to test the value of this workflow. Analysis of inversion results are performed that finds a correlation between regions of geological uncertainty and geophysical misfit. This correlation strongly suggests that geological uncertainty can be used as a powerful geological constraint to optimise inversion processes and produce geologically reasonable models.
© 2013 ASEG