--> Abstract: Fracture Characteristics and Variability within a Basement-Cored Laramide Age Anticline, Teapot Dome, Wyoming, by S. P. Cooper, L. B. Goodwin, J. C. Lorenz, and L. W. Teufel; #90937 (1998)

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Abstract: Fracture Characteristics and Variability within a Basement-Cored Laramide Age Anticline, Teapot Dome, Wyoming

COOPER, SCOTT P., and LAUREL B. GOODWIN, Department of Earth And Environmental Science, New Mexico Tech; JOHN C. LORENZ, Sandia National Laboratories; LAWRENCE W. TEUFEL, Department of Petroleum and Chemical Engineering, New Mexico Tech

Teapot Dome is an asymmetrical, basement-cored anticline located at the southwestern edge of the Powder River Basin. A systematic study of fracture characteristics and variability was undertaken in an attempt to develop a model describing fracturing associated with basement-cored anticlines in the Rocky Mountain region. Most field measurements were taken from strata within the Cretaceous Mesaverde Group. Variability of fracture patterns was found related to both structural position and lithology.

Fracture characteristics and structures vary as a function of structural position as follows: 1) Bed-normal extension fractures dominate strata on the eastern limb. 2) Northeast striking normal faults are common on the eastern limb but are rare on the western limb. 3) The western limb is segmented into distinct areas displaying different fracture characteristics. 4) Conjugate fractures and deformation bands are common in the southwestern limb and southern are of the anticline. 5) The southern arc contains several previously unrecognized faults striking subparallel to the north-northwest trending axis of the anticline.

Fracture characteristics also change as a function of lithology. Such changes include: 1) Fracture intensity increases with increased cementation. 2) Fracture spacing increases proportionally with bed thickness. 3) Coal cleats are generally oblique, by up to 20 degrees, to fractures in sandstones. 4) Most fractures in sandstone units terminate at contacts with shale layers. 5) Deformation bands occur almost exclusively in the poorly cemented beach-sand facies of the Mesaverde Group.

The positive or negative impacts of the observed structures on fluid flow in subsurface reservoirs will be discussed.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah