Luncheon – October 7, 2005

Title: Structural Compartmentalization at Cave Gulch Field, Wind River Basin, Wyoming
Speakers: Neil Hurley, Kim Doupé, and Mike Sherwood, Colorado School of Mines, Golden, Colorado
Luncheon Date: October 7, 2005
Publication: The Outcrop, October 2005, p. 4

Cave Gulch Field, located in the Wind River Basin, Wyoming, produces gas mainly from stacked fluvial sandstones of the Paleocene Fort Union and Upper Cretaceous Lance formations. The field is a faulted anticline that lies in the footwall of the Owl Creek Thrust.

Formation MicroImager (FMI) logs covering 62,000 ft (18,898 m) of vertical section are available in 11 wells in Cave Gulch Field. These logs were interpreted for bed boundaries, fractures, and microfaults. Bed boundaries in interbedded shales were used to create cumulative dip, dip azimuth vector, and statistical curvature analysis technique (SCAT) plots. Inflection points on these plots are interpreted as subseismic-scale faults.

Published structure maps of the top of the Lance and underlying Meeteetse formations were used to build a 3D geologic model. This model includes 3 deterministic seismic-scale faults. Subseismic-scale faults were generated using a grid-based fracture generator. The model was constructed based on microfault orientations interpreted from FMI logs, and the depths to subseismic-scale faults interpreted from dip-domain analysis of FMI data. After generating subseismic-scale faults, a horizontal plane was cut through the model at the middle of the Lance Formation. Area sizes for fault-bounded compartments ranged from <1 to 387 ac (<0.004 to 1.6 km2). Well spacing templates of 5, 10, 20, 40, 80, and 160 ac (0.02, 0.04, 0.08, 0.16, 0.32, and 0.65 km2) have been superimposed on the model to estimate the drainage efficiency of various infill-drilling programs.