Middle Bakken Revisited: Petrophysical Aspects of the Subcrop Fairway

Hansen, William B. ¹ (1) Consulting Geologist, Jireh Consulting Services, Great Falls, MT

A basin-wide study of the Bakken Formation was conducted on the US side of the Williston Basin, focusing on the petrophysical aspects of the middle member that corresponded to free oil shows from DST’s. Every vertical test that intersected the Bakken was examined. It was discovered that free-oil shows on DST’s of the Bakken interval corresponded well with apparent water-resistivity calculations in the Middle Bakken member of 0.1 (Rwa = 0.1). The initial results of this study were published over ten years ago (Hansen and Long, 1991) and recommended at that time the middle member be considered a horizontal drilling candidate, especially in areas where the Rwa calculations corresponded well with an isopach map of the Middle Bakken porosity. The middle Bakken subcrop “fairway” of Hansen and Long (1991) will be re-examined in this paper, in light of the recent horizontal and multi-lateral drilling activity in eastern Montana and North Dakota.

AAPG Search and Discovery Article #90055©2006 AAPG Rocky Mountain Section Meeting, Billings, Montana