The Upper Bakken Shale Play, Elm Coulee Field, Williston Basin
The Upper and Lower Bakken shales are the source beds for the Bakken Petroleum System of the Williston Basin. Reservoirs for this system include the shales, the lower Lodgepole, Middle Bakken silty dolostones, and Three Forks silty dolostones. The Upper shale was a drilling target in the late 1970s through the early 1990s in southwest part of the basin in North Dakota (termed the depositional limit play or Billings Nose play). The discovery of the giant Elm Coulee Field changed drilling strategies to focus on the Middle Bakken dolostone member. As this play extended into North Dakota, drilling success was also encountered in the upper Three Forks dolostones. The Upper Bakken shale has recently been targeted with horizontal drilling and multistage fracture stimulations along the southwest edge of Elm Coulee Field where the Middle Member pinches out. In this area wells are drilling into the Upper shale and then completed with multistage fracture stimulations. The fracture stimulations extend into the adjacent Lodgepole and Three Forks formations. So in essence, these new wells target multiple pays. Factors thought to be important in this Upper shale play include: orientation of horizontal laterals, bed thickness, natural fractures, shale mineralogy, abnormal pressure, and TOC content. This play is a similar to the previous depositional limit play in North Dakota except the wells are completed with multistage fracture stimulations. Exploration success in the Upper Bakken shales suggests that future drilling should also target the Lower Bakken shales.
AAPG Datapages/Search and Discovery Article #90193 © 2014 Rocky Mountain Section AAPG Annual Meeting, Denver, Colorado, July 20-22, 2014