Vajdova, Veronika1, Sheryl Tembe1, Patrick Baud2, Teng-fong
(1) SUNY at Stony Brook, Stony Brook, NY
(2) Laboratoire de Physique des Materiaux, IPG de Strasbourg, Cedex 67084, France, Strasbourg, France
ABSTRACT: Laboratory Investigation of Compaction Localization and its Coupling with Fluid Flow
Compaction localization has been described in formations of porous rocks such as sandstone, unconsolidated sand or non-welded ingnimbrites. The localized structures affect local fluid flow, and depending on the compaction zone properties the flow may be inhibited or even enhanced. The coupling of compaction and localization has been studied in the laboratory in recent years. Two end-members of this failure mode, that develops perpendicular to the maximum compression, have been identified: numerous discrete compaction bands with thickness only several grains, or a few diffuse bands that are significantly thicker. Much of what is known about discrete compaction bands derives from triaxial compression experiments performed on the homogeneous Bentheim sandstone with porosity 23.0%. Recently we observed similar compaction localization behavior in Diemelstadt sandstone with initial porosity of 24.4%, higher content of feldspar and strong bedding corresponding to low-porosity laminae. To evaluate the effect of the compaction band formation on the fluid flow we measured hydraulic permeability in Bentheim sandstone. We observed a large drop in permeability upon the formation of the first bands. With bands accumulating the permeability decreased more gradually. Since field studies indicate compaction band initiation from stress inhomogeneities we investigated initiation and propagation of compaction bands in samples of Bentheim sandstone with a circumferential notch introduced as a stress concentrator. Mechanical data and microstructure showed compaction bands initiating at the notch-tip and propagating sequentially inwards. The laboratory studies have elucidated how pressure, lithology and stress concentration influence development of compaction localization and its coupling with fluid flow.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.