Davies, Russell1, David W. McDonald2, Alton Brown3,
Rob Knipe1
(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.