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Characterization of Properties in Deformation Bands


Strain localization in porous sediments (deformation bands) can alter reservoir flow and induce compartmentalization. Deformation bands from several cores were identified and characterized. Their spacing, thickness and facies association were measured. A variety of deformation mechanisms interior to the bands were found to control their physical properties. These included clay smearing, cataclasis, and subsequent partial cementation. In this study we have identified the deformation mechanisms within the bands and the compaction state of the host reservoir. The magnitude of the respective mechanisms was a function of framework mineralogy, compaction state at the onset of band formation, and subsequent temperature and burial history. The relative magnitudes of these mechanisms determined their resulting impact on reservoir flow properties. Thin section analysis has been integrated with the core analysis measurements. A full range of measurements and images were used to characterize the host rock and bands at in-situ conditions. Stress dependent compressibility, permeability and acoustic properties have been measured both in the non-deformed host rock, and in samples containing deformation bands. Micro-CT scanning was performed on the whole core to determine the optimum location and orientation of the samples that were measured. Pre- and post-test CT scans and thin section analyses were performed to establish initial and final properties of the measured sample. Integration of measurements with the corresponding images was performed to identify and quantify the deformation mechanisms.