Bozkurt N Ciftci¹, Alexander Aviantara¹, Dennis Kerr², Neil F. Hurley¹

(1) Colorado School of Mines, Golden, CO
(2) The University of Tulsa, Tulsa, OK

ABSTRACT: Outcrop based 3-D modeling of the Tensleep Sandstone at Alkali Creek, Bighorn Basin, Wyoming

Bounding surfaces act as permeability barriers or baffles to fluid flow and divide the Tensleep reservoirs into flow compartments at different scales. In order to identify the geometry and volumetric size of these compartments, a 3-D computer model of the Tensleep Sandstone was constructed based on the outcrop exposures. The field data were collected by a precise GPS receiver system at Alkali Creek, Bighorn Basin, Wyoming. The data include coordinates and elevations of 3500 data point that are tied to 0.0-, 1.0-, 0.1- and 2.0-bounding surfaces.

1.0-bounding surfaces display undulatory geometry both in the foreset dip and strike direction. They climb from 0.0-bounding surfaces in the general direction of foreset dip with an angle typically less than 1°. 1.0-bounded compartments are laterally extensive across the study area and display variable thicknesses in the range of 2 to 26 meters. These compartments are further subdivided into smaller 2.0-bounded compartments by 2.0-bounding surfaces. 2.0-bounding surfaces have average spacings of 30m and display variations in their strike orientation forming laterally discontinuous 2.0-bounded compartments.

Wells were simulated by 10-acre, 20-acre, 40-acre and 160-acre templates on the 3-D model. The simulation also includes horizontal wells that are oriented parallel, perpendicular and oblique to foreset dip direction. For each well, the volume of intersected reservoir compartments was calculated. Comparison of these volumes with the ideal drainage volume of wells identified the most efficient drill template for the Tensleep reservoirs. Horizontal wells drilled parallel to foreset dip direction drain the maximum number and volume of reservoir compartments.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado