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Horizontal Stress Development in Fine-grained Sediments and Mudstones during Compaction and Uplift
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 73rd EAGE Conference and Exhibition incorporating SPE EUROPEC 2011, May 2011, cp-238-00691
- ISBN: 978-90-73834-12-5
Abstract
Knowledge of Ko, the ratio between horizontal and vertical effective stresses, is important for understanding development of horizontal stress during compaction and uplift in sedimentary basins. In this paper recent experimental data of Ko of natural and synthetic mudstones are presented. A series of uniaxial strain tests (Ko consolidation) has been performed on 10 synthetic sand-silt-clay mixtures and seven natural Barents Sea mudstone samples from the Hekkingen and Fuglen formation of Upper Jurassic age. The development of Ko in synthetic and natural samples is compared during the compaction and unloading phases. For a given synthetic mixture of one clay component (illite) and silt there is a strong correlation of the fraction of clay on the Ko value. Various fractions of pure kaolinite and illite gave minor differences on the Ko value. These variations of Ko in the clay and silt mixtures can probably be explained by variations in friction angle,which is previously shown to be a critical parameter for development of Ko during compaction and unloading in uncemented sediments. The relations for Ko derived for uncemented sediments do not apply directly during compaction and unloading of the cemented Barents Sea mudstones.