--> --> ABSTRACT: Analyses of Permeabilities of Faulted Sandstone in a Subseismic Fault, by James P. Evans and Zoe K. Shipton; #90906(2001)
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James P. Evans1, Zoe K. Shipton1

(1) Utah State University, Logan, UT

ABSTRACT: Analyses of Permeabilities of Faulted Sandstone in a Subseismic Previous HitFaultNext Hit

We determine the structure and permeability variations of a 4-km-long normal Previous HitfaultNext Hit by integrating surface mapping with data from five boreholes drilled through the Previous HitfaultNext Hit (borehole- to tens of metre-scale). The Big Hole Previous HitfaultNext Hit outcrops in the Jurassic Navajo Sandstone, central Utah. A total of 363 m of oriented core was recovered at two sites with displacements of 8 m and 3-5 m. The main Previous HitfaultNext Hit core is 0.3 - 1.2 m thick and is composed of low-porosity amalgamated deformation bands with slip-surfaces on one or both sides. Previous HitFaultNext Hit thickness is not a function of displacement, and can vary over strike distances of several metres. Minipermeameter measurements show a permeability decline from >2000 md to 1.5 md near the Previous HitfaultNext Hit. Whole-core tests show that Previous HitfaultNext Hit core permeability is less than 1 md, and individual deformation band permeability is 0.9-1.3 md. Using these results we calculate bulk permeability across and along the Previous HitfaultNext Hit zone. Calculated transverse permeability over 5-10 metres is 30-40 md: approximately 1-4% the value of the host rock. Previous HitFaultNext Hit parallel transmissibilities are 70-90% of the host rock. An inverse power mean calculationfor a complex array of orthorhombically oriented faults yields transmissibilities 20-60% of the host rock. The bulk Previous HitfaultNext Hit zone permeability is most sensitive to Previous HitfaultNext Hit core thickness, which exhibits the greatest variability of the Previous HitfaultTop components examined.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado