Date of Award

January 2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Richard D. LeFever

Abstract

The Duperow Formation of southwestern North Dakota is Devonian in age, and forms the lower part of the Jefferson Group within the Kaskaskia Sequence. This shallow marine shelf deposit is a cyclical carbonate evaporite, and is comprised of dolomitic mudstones, gypsum, multiple bioclastic wackestones/packstones, stromatoporoid boundstone and anhydrite.

There is a long history of oil production in this formation dating back to the 1950’s in North Dakota. By 1989, the Duperow Formation was the second most prolific hydrocarbon producer on the Billings Anticline in North Dakota, and therefore was studied extensively. Environmental factors during deposition as well as diagenetic processes after deposition allowed for hydrocarbon accumulation in pore spaces. As technology advanced and unconventional plays developed, small pay and traditional reservoirs, like the Duperow, were not as profitable, and because of that very little research was done on the Duperow in North Dakota 1989.

The well-established cycles of the lower Duperow Formation allow for correlation of wells and cycles across the basin. Two of these cycles at the base of the Duperow have enhanced porosity and definite permeability in locations where dolomitization has occurred and stromatoporoid banks accumulated. Dolomitization of limestone increase the porosity of the rock as the dolomite crystals take their shape as rhombohedrals. Stromatoporoid banks keep some of its pore space and permeability as it is fossilized making it suitable to be a reservoir. These cycles are shown to be continuous beyond the slopes of the anticline. The creation of a 3-D geocellular model shows the extent of the porosity and permeability throughout the study area.

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