Date of Award

January 2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Richard LeFever

Abstract

With recent advancements in hydraulic fracturing and horizontal drilling technologies, there has been an increase in the production of hydrocarbons from unconventional reservoirs in the Williston Basin. The basin underlies parts of North Dakota, Montana, and South Dakota in the U.S. The Three Forks Formation in Williston Basin is an example of an unconventional reservoir that, according to the United States Geological Survey (Gaswirth, et al., 2013), has a potential of yield of 3.7 billion barrels of unrecovered oil. Charlson Field, located in McKenzie County, is a primary target for the Three Forks Formation, which has shown high potential for production with an increase in interest for further exploration. To enhance our knowledge of the field and locate prolific regions for future drilling, studies were conducted, including geological and petrophysical properties analysis for the means of oil in place (OIP) calculations.

The Devonian Three Forks Formation is unconformably overlain by the Bakken Formation and underlain by the Birdbear Formation. It is stratigraphically divided into five members. For the purpose of petroleum exploration and production, operators in the basin have identified four different benches through the Three Forks. The four benches are used to determine where the potential reservoirs are in the rock unit. The four benches were selected based on core analysis and distinguished from one another by their well log signatures.

In this study, the Three Forks Formation was evaluated from a lithological and petrophysical point of view. The preliminary step was to distinguish the pay zones, dolomitic beds, from the non-productive shaly beds. The productive zones were given a numbered bench that was determined from the well log and core study. After digitizing the well logs using NeuraLogTM, petrophysical properties such as porosity and water saturation were calculated by using PetraTM. Finally, oil in place was calculated under volumetric methods by using estimated saturation, porosity and net pay from the well and log core data. This study provided us with an insight to the more suitable areas in Charlson Field where future operations should be conducted.

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