Another Look at Hartzog Draw Stratigraphy, Powder River Basin, WY

Painter, Clayton S. and Randi S. Martinsen
University of Wyoming, Laramie, WY

     Hartzog Draw, a large oil and gas field, within the Powder River Basin, Wyoming, produces from the Campanian Shannon Sandstone. The Shannon has been the focus of numerous papers and much oral debate, yet there is little consensus regarding its origin and depositional setting. Furthermore, the current operator within Hartzog Draw has encountered difficulties with water flooding the Shannon. Although the water floods appear successful at first, before too long the reservoir abruptly ceases to accept further flooding, and this could indicate a lack of understanding of the Shannon Sandstone's stratigraphy in Hartzog Draw.
     A new data set of over 50 cores from Hartzog Draw has been made available and it allows us to closer examine the reservoir's stratigraphy and its possible subtleties that could be causing unsuccessful water flooding. We performed detailed descriptions of these cores, created cross sections across the length and width of the Hartzog Draw and studied samples of the Shannon Sandstone in thin section. Throughout the study particular attention was paid to possible attributes that could cause a cessation of water intake such as barriers causing compartmentalization and the presence of expansive clays. We believe that these descriptions could help current oil and gas producers to better understand the nature of the reservoir's architecture and overcome current complications. In addition to helping overcome present production complications, we believe that our new insight into the detailed stratigraphy of the Shannon Sandstone can be applied to better understanding the long-debated history of its deposition and preservation.

AAPG Search and Discovery Article #90071 © 2007 AAPG Rocky Mountain Meeting, Snowbird, Utah