ABSTRACT

Important oil producing units in southern Burke, northern Mountrail and northeastern Ward counties generally are below the State A marker in the Coteau, Bluell, and Sherwood beds of the Mississippian Madison Group. Eleven oil fields in this area have produced from one or more of these units. To the north of this area, oil producing units are stratigraphically higher, primarily the Mississippian Rival subinterval of the Frobisher-Alida interval and the Midale subinterval of the Ratcliffe interval of the Madison Group.

Oil production generally occurs below northeast to southwest trending elongated thickenings, or "noses", of the Ratcliffe interval. These noses are clearly seen on isopachous maps of the Ratcliffe. Another useful indicator of these noses is the edge of the F salt. The salt edge generally trends northwesterly and diagonally across this area, and outlines the noses.