RELATING STRATIGRAPHY, LITHOLOGIC FACIES, AND 3D SEISMIC ATTRIBUTES TO OIL PRODUCTION IN BAKKEN FORMATION WELLS, RED SKY AREA, WILLISTON BASIN, NORTH DAKOTA

The Bakken Formation is considered the most important hydrocarbon-bearing rock unit in the Williston Basin of North Dakota and is currently one of the most prolific unconventional resource plays in North America with a 2015, basin-wide production of approximately 1.1 million barrels of oil per day. Most production from the Bakken Formation is from wells drilled horizontally and completed using hydraulic fracturing in the relatively thin Bakken formation that varies in thickness from 0 to 160 feet (0 to 49 meters). Studies by previous workers in the Williston basin have identified six, field-scale “sweet spots” characterized by higher production relative to other areas of the Williston Basin. Previous workers have also recognized that significant variation in hydrocarbon production exists even at scales of 1000’s of feet to a few miles between individual wells within these known sweet spots. The objective of this thesis is to understand the causes of these localized, field-scale, production variations and how to best optimize future wells and completions. Unlike previous studies that focused on regional-scale sweet spots, the work presented here focuses on the field level, which is scale for drilling and completion decisions. I present an integrated interpretation of the geology, geophysics, and drilling and completion designs of wells targeting the Bakken Formation in the Red Sky area, Mountrail County, North Dakota, in order to explain localized variations in well productivity using my compilation of historical production statistics. Using a high-quality, time-migrated, 3D seismic survey combined with well logs, core data, well files, seismic attributes, and production statistics, I have identified the productive reservoir unit and its natural fracture patterns over an area of approximately 730 square miles. Using ArcGIS spatial analysis and TIBCO Spotfire analytical software, I present a simple method to quantify variations in historical production statistics and how these variations reflect geologic controls including facies and fracture patterns. Geologically, the most significant control on the “sweet spot” are thick sand bodies of the Middle Bakken Formation deposited in a tidal dominated barrier bar system. Structurally, the most significant control on sweet spots are areas of the least number of natural fractures as mapped using seismic attributes.