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Ryan D. Christensen1, Mark P. Fischer1, M. Scott Wilkerson2
(1) Northern Illinois University, De Kalb, IL
(2) DePauw University, Greencastle, IN

Abstract: Timing, Distribution, and Controls on Fracture Systems in the San Rafael Swell, Utah: Implications for Fracturing in Laramide-Style Fault-Propagation Folds

Successful development of fractured reservoirs in anticlinal traps requires an understanding of the controls on fracture formation and knowledge of the spatial distribution of fracture orientations. This study uses detailed fracture analysis of the Jurassic Carmel Formation along the eastern limb of the San Rafael Swell and three-dimensional trishear modeling of fault-propagation folds to gain insight into structural and stratigraphic controls on fracture system architecture. Field observations allow for correlations among fracture system architecture, bed thickness, lithology, and structural position. Cross-cutting relationships and mesoscopic structural analyses allow for interpretations about kinematic history and paleo-stress trajectories. Analysis of fracture system architecture at several different structural positions suggests each area has a unique, local fracturing history. One example of this is that cross-fold joint orientations vary with respect to local strike, suggesting that they formed with respect to localized stress fields rather than the regional tectonic stress field.

To further understand these local fracturing histories, we conducted a number of three-dimensional trishear fault-propagation fold models. Trishear modeling of fault-propagation folds documents the effect of geologic variables, such as fault dip, fault geometry, and fault displacement profile, on fold evolution and geometry. Curvature and dip magnitude analyses on the evolving model surfaces allow us to predict theoretical fracture patterns and intensity throughout a fold. These predictions are compared with fracture data from the San Rafael Swell and we are currently working to compare these models with data from similar Laramide-style structures.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana