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Workreport 2007-7

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Name:

Selected Visualizations and Summaries of the Contents of the Fracture Database, Deformation Zone Intersection Data, and Deviation Survey Measurements Regarding Boreholes OL-KR1--Ol-KR33B

Writer:

Kuusisto, S. & Lehtokangas, M.

Language:

English

Page count:

117

Summary:

Posiva Oy has acquired an extensive amount of data on the geology of the Olkiluoto Island. An important part of that data is the heterogeneous collection of fracture information, known as the fracture database. In this work, the fracture database was studied and analyzed using data mining techniques aiming to characterize the properties of the database itself, not the underlying geological and physical laws and phenomenona that are reflected through the data. The goal was to discover previously unknown correlations, patterns, and properties contained within the data. In addition to the fracture database, two supporting datasets were utilized in the analysis: deformation zone intersection data and deviation survey measurements.

The following analyses were carried out: logical discrepancies and potential errors in data; statistics of alphanumeric strings, numeric values, and empty fields; visualizations of borehole locations and shapes; histograms, ranges, quantizations, 1- and 2-dimensional clustering of numeric quantities; core orientations; comparison between reported fracture orientations with those recalculated using the core orientations and fracture orientations with respect to core; fracture densities; fracture orientations at intersections of each deformation zone separately; statistics of zone intersection data; discovery of groups of valid fields in the database; discovery of quantities that predict the lithology or hydraulic conductivity of fractures; discovery of fracture fillings that have a tendency to appear together.

The interpretation of the analysis results was beyond the scope of this work. The assessment of the novelty and the usefulness of the discovered patterns and relationships requires domain expertise and familiarity with the everyday practises on how the data is utilized, what assumptions are satisfied and which aspects are significant. Instead, this report gives numerous different viewpoints on the data and through them, brings up issues that might require further investigation or just verifies the current conception of issues related to the geology of Olkiluoto Island.

Keywords:

Fracture database, data mining

File(s):

Selected Visualizations and Summaries of the Contents of the Fracture Database, Deformation Zone Intersection Data, and Deviation Survey Measurements Regarding Boreholes OL-KR1--Ol-KR33B (pdf) (3.7 MB)


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