Structural core logging

Task Geoscience provides a comprehensive structural core logging service, with full integration of data to borehole images. Core analysis provides an important ground-truthing element to any borehole interpretation, yielding information about image resolution, structural tilt, fracture fill characteristics and cross-cutting relationships. The features logged can play an important role in the degree of reservoir communication and in the relative importance of matrix versus fracture network in hydrocarbon production.

Structural core logging

• Logging undertaken worldwide.
• Concerned primarily with structural discontinuities intersecting the borehole.
• Structural tilt calculation in oriented core.
• Can be integrated with other core studies, e.g. goniometry and sedimentological logging, borehole image analysis.

Approach

• Examination of both the whole core and slabbed sections is preferred.
• If possible, we clean exterior of whole core.
• Core re-fitted.
• For slabbed core, linear sample trace taken through centre of the slab.
• Digital images taken of key features.

Features typically logged

• Bedding features, particularly palaeohorizontal indicators.
• Fractures: classified according to aperture, fill, geometry and morphology, association with other geological features, genesis (natural or induced), etc.
• Along-hole fracture spacing.
• Faults, normal, reverse, undetermined.
• Fault throw where determinable.
• Cross-cutting relationships.
• Nature of any mineral fill. Fill width and continuity.
• Apparent apertures. Porosity to fill proportions.
• Slickenside and lineations along surfaces. Pitch angles.
• Relationship of fracturing to lithology and bed thickness.
• Stylolites and stylolite associated fractures. Stylolite form and amplitude.
• Petal centre line fractures.
• Core disking.
• Apparent inclinations on the slab or through core. True orientations if possible.
• Other structural discontinuities, baffles, barriers or flow paths.

Analysis

• Fracture types and sets detailed.
• Fracture network continuity and communicability assessed.
• Fracture sets identified and spacings calculated.
• Fracture densities derived.
• Fault-throw scaling relationships determined.
• Matching of bedding dips in unoriented core to structural dip from seismic or other sources allows estimation of true feature orientations.

Data presentation

• Spreadsheets of (apparent) feature orientations versus depth.
• Digital and hardcopy graphical products.
• Permanent acetate record available for complex sections.
• Integration with other data sources: core goniometry, sedimentological core logging, borehole images and seismic data.
• Written reports.

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