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The AAPG/Datapages Combined Publications Database

Fort Worth Geological Society

Abstract

Southwest Section AAPG Convention. March 1-4, 2003.

ABSTRACT: Outcrop Analogs to Subsurface Fractured Reservoirs, Arbuckle Mountains, Oklahoma

By

Russell K. Davies1 and Alton Brown2

1Rock Deformation Research, P.O. Box 2998, McKinney, TX 75070 ([email protected])
2
([email protected])

Fractures studied in four outcrops aid prediction of fracture characteristics in subsurface reservoirs. Outcrops are simple folds with shallow and deep maximum burial, complex secondary structures, and Previous HitfaultNext Hit-bounded structural highs. The simple fold with shallow maximum burial shows dominant fracture sets sub-parallel and orthogonal to the fold axis. Most fractures terminate at bedding Previous HitplanesNext Hit. Small thrusts within beds demonstrate the importance of layering slip. Tectonic stylolites are rare and indistinct. At greater maximum burial, fracture patterns are dip and strike oriented, but en-echelon shear fractures are locally important and tectonic stylolites are abundant. A prominent, near vertical fracture set cuts bedding sub-parallel to a regional normal Previous HitfaultNext Hit trend. This fracture orientation may be related to regional rather than local deformation. Fracture sets within complex structures form a complex, heterogeneous fracture pattern. The heterogeneous fracture distribution within adjacent Previous HitfaultNext Hit blocks makes their prediction in subsurface reservoirs difficult. Fractures in Previous HitfaultTop-bounded highs deformed at shallow burial depth show increasing intensity and geometric variability proximal to faults. These form a strongly deformed damage zone. Small fractures confined to single beds are not simply related to orientation of bounding faults or dip. Larger through-going fractures lie along the regional trend. Fractures in chert nodules are dilated, open and more closely-spaced than the surrounding limestone. Together, these results indicate that general characteristics of fracture systems can be predicted from structural style, lithology, and burial depth during deformation. Mineralization of fractures in this old fracture system is related to burial history since deformation.

 

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