The upper Red River Formation in Western North Dakota consists of cyclic sedimentary rocks having four main porosity zones which contain most of the oil and gas found in the formation. It was divided into three distinct units that were traced throughout western North Dakota on mechanical logs. In ascending order these are the P, R, and F intervals which consist of alternating sequences of dolomites, limestones, and anhydrites. Facies changes, occur within the P interval both on a regional and a local scale, typically from dense limestones to porous dolomites.
The Kesson anticline and the basin hinge JJ.ne 1-1ere the most active structural area affecting the deposition of upper Red River sediments. A knob or high relief on the anticline had a localized effect on sedimentation. Rapid thinning in all intervals of the Red River near the central part of the state indicate the effect of II the hinge line. Other structural features defined on isopachous maps include the Mercer High, Divide Low, Ward High, and Billings Nose.
X-ray and microscopic analysis of selected samples of cores from the upper Red River Formation indicate that the main porosity zones consist primarily of secondary dolomite.
Oil accumulations in the Red River Formation are primarily in structural traps, but local changes in lithology and grain size