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RABA'A ALI, CRAIG VAN KIRK, and NEIL HURLEY, Colorado School of Mines, Petroleum Engineering Dept., Golden, CO

ABSTRACT: Fluid Flow in Fault Zones: Reservoir Simulation Study of High Directional Permeability, Little Sand Draw Field, Big Horn Basin, WY

Little Sand Draw field is one of many northwest trending, hydrocarbon producing Laramide anticlines that occur in the Big Horn basin. Outcrop studies performed at nearby analogous surface anticline show that there are many small tear faults formed at high angles (roughly perpendicular) to the fold axis. Pressure interference data in Little Sand Draw field suggest the existence of those tear faults because of high directional permeability, roughly perpendicular to the fold axis.

A full-field reservoir model of Little Sand Draw was constructed using the ECLIPSE black-oil simulator to history match the field's past production performance. Fluid-flow models have been created with and without tear faults to test the significance of faults to the history match. Spacing and orientation of tear faults in the faulted model are based upon outcrop measurements.

The simulation procedure includes a history match that covered 49 years of recorded history, and involved a comparison of measured pressure, water-oil ratio, and water production with those calculated by the model. Results indicate that high directional permeability tear faults play a major role in obtaining a reasonable match in the whole field. Furthermore, the relative permeability curves, fault-matrix transmissibility, aquifer support, and anistropic matrix permeability `Kmy' are important factors that assist in obtaining a realistic history match.

AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid