 Fracture orientations can be measured on cores both by goniometer and by digital core scanning. For goniometer measurements, the cored interval of interest is first oriented using deviation and structural data or palaeomagnetic analysis. A Main Orientation Line (MOL) is drawn on the core, oriented to magnetic North or maximum dip. Using the MOL as a reference line, the dip, strike and azimuth of fracture planes are measured using either a computer goniometer or an Eastman Christensen mechanical goniometer. If the well is deviated, the fracture data set is rotated back to vertical and th data are interpreted using rose plots, dip-direction plots, fracture density displays and fracture distribution with depth.
A 360-degree digital core scan can be made for each core segment throughout the interval of interest. These box length scans are added and fitted together, creating larger aligned core intervals. Using distinct fractures on the scanned core images and matching their orientations to similar distinct fractures picked on the borehole images, the aligned core intervals are oriented according to the borehole images. |
· Type of displacement (extensional, compressional, strike-slip)
· Morphology (planar, non-planar)
· Magnitude of apparent displacement (none, mm, cm, dm)
· Fracture fill (sediment and/or mineral cement, open or (partially) cemented)
· Nature of fracture boundaries (diffuse or sharp)
These categorized, oriented fractures as picked on the core are then imported into the software package WellCAD for display and further evaluation.
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