Abstract

Hydrostatic and triaxial compression experiments have been conducted to investigate the evolution of fluid permeability and fluid storage capacity in Tennessee sandstone, a low- porosity tight' reservoir sandstone. A newly developed single-ended transient pulse permeability measurement technique has been used for this study. Under hydrostatic stress, both permeability and specific storage are demonstrated to be dependent upon effective confining pressure. The evolution of axial permeability as a function of increasing compressive deviatoric axal sttess has been investigated in triaxial compression experiments. All samples were deformed within the brittle faulting regime. Both permeability and specfic storage decrease during compaction, and subsequently increase when axially-aligned dilatant microcracking becomes dominant. Brittle failure is sometimes accompanied by a transient increase in permeability by as much as 1.5 orders of magnitude. Following brittle failure the permeability is controlled by the properties of the fault rock. Permeability decreases as stable sliding occurs on the fault up to large axial strains, such that the fault may act as an impermeable seal to migrating fluids.

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