Davies, Russell1, David W. McDonald2, Alton Brown3,
(1) Rock Deformation Research, McKinney, TX
(2) Consultant, Plano, TX
(3) Consultant, Richardson, TX
ABSTRACT: Fracture Characterization Across a Complex Structure: Arbuckle Anticline, Oklahoma
Detailed mapping of fractures was conducted within the Lower Paleozoic of the asymmetric Arbuckle anticline, Oklahoma. Outcrop mapping of fractures in an active petroleum system can improve prediction of hydraulically conductive fracture sets in the subsurface. Outcrops along I-35 define a north-south transect across the anticline. Fracture characterization included orientation, spacing, length, width, and timing. Fracture sets in carbonate, shale and sandstone units are related to the Pennsylvanian age Ouachita – Marathon Orogeny. The results show the dominant fracture sets on the back-limb of the fold trend NNE to NE with steep SE and NW dip. The NNE set form a common through-going set of fractures that are most likely hydraulically significant. A wide range of secondary fractures oriented E-ESE and SE with moderate N and NE dips are also observed in outcrop, but are less systematic. No persistent set of strike-parallel faults is observed across the shallow dipping limb. The fracture character is a function of the lithology, bed forms and thickness. Limestone units with thinly bedded chart layers had the greatest number of fractures with massive limestone units the least. Additional analysis focused on the density of fractures versus lithologic type and on the relationship of fractures to faults and minor folds within the basin. Fractures in the overturned forelimb show a well-developed set of strike-parallel faults. The NE trending fracture sets mapped on the shallow dipping limb are absent. The mapped fracture sets can not be predicted from simple curvature analysis, but are most likely related to the hinge migration and folding of the layers.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.