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Permeability and permeability anisotropy in Crab Orchard sandstone: Experimental insights into spatio-temporal effects
Ist Teil von
Tectonophysics, 2017-08, Vol.712-713, p.589-599
Ort / Verlag
Amsterdam: Elsevier B.V
Erscheinungsjahr
2017
Link zum Volltext
Quelle
Elsevier ScienceDirect Journals Complete
Beschreibungen/Notizen
Permeability in tight crustal rocks is primarily controlled by the connected porosity, shape and orientation of microcracks, the preferred orientation of cross-bedding, and sedimentary features such as layering. This leads to a significant permeability anisotropy. Less well studied, however, are the effects of time and stress recovery on the evolution of the permeability hysteresis which is becoming increasingly important in areas ranging from fluid migration in ore-forming processes to enhanced resource extraction. Here, we report new data simulating spatio-temporal permeability changes induced using effective pressure, simulating burial depth, on a tight sandstone (Crab Orchard). We find an initially (measured at 5MPa) anisotropy of 2.5% in P-wave velocity and 180% in permeability anisotropy is significantly affected by the direction of the effective pressure change and cyclicity; anisotropy values decrease to 1% and 10% respectively after 3cycles to 90MPa and back. Furthermore, we measure a steadily increasing recovery time (10–20min) for flow parallel to cross-bedding, and a far slower recovery time (20–50min) for flow normal to cross-bedding. These data are interpreted via strain anisotropy and accommodation models, similar to the “seasoning” process often used in dynamic reservoir extraction.
•New data on effects of stress-path, pressure and anisotropy on fluid permeability.•Irreversible and cum. Change in permeability, porosity and acoustic wave velocity.•Two key phases for permeability reduction have been identified.•Fluid flow parallel to bedding showed a particularly strong hysteresis.•Findings can likely be applied to any low permeability, anisotropic rock formation.