--> Evolution of Reservoir Characterization and Well Optimization in the Bakken/Three Forks Play

AAPG Annual Convention and Exhibition

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Evolution of Reservoir Characterization and Well Optimization in the Bakken/Three Forks Play

Abstract

Since the initial Bakken discovery well in 1957, over 8000 Bakken and 1600 Three Forks wells have been drilled across North Dakota, Montana and Saskatchewan. Over the past decade we have seen a rapid uptick in the geologic understanding of the Bakken and Three Forks, coupled with increasingly effective, and efficient, customization of drilling and completions. We illustrate how the emergence of geologic data coverage has driven industry understanding of play nuances. Regional structural, thickness and geochemistry maps highlight early play characterization and identification of the eastern "line of death" and unique characteristics of the Sanish and Parshall fields. Lithofacies classification of vertical well log suites illustrate the insights gained from delineation wells that framed interpretation of the complex play stratigraphy. More recently, sufficient well coverage has emerged to consistently map oil saturation/water cut across the basin; supported by more detailed depth and character mapping using the extensive gamma-ray coverage. Keeping pace with burgeoning geologic understanding, well completion techniques have been tested and tuned - from single to 40 and 50 stages - with sand volumes ranging well above 10 million pounds and accompanying fluids beyond 150,000 barrels. Currently, multi-lateral co-development of Bakken and two-to-four Three Forks formations are becoming standard operating procedure. "Frac hits" have emerged as the key development optimization focus as well spacings approach 500 feet in common formations and 250 feet in staggered multi-level patterns. While overlapping zones of stimulation can have beneficial effects, delayed infills are proving to be very problematic with unclear economic tradeoffs of increased, though contested well production, often offset with dramatic production decline in adjacent, active wells. Oilfield analytics provide a unique perspective of the ongoing efforts to "right size" drilling and completions engineering for rock and fluid characteristics in the Bakken and Three Forks reservoirs. Dynamic well spacing, vertical and lateral geometry, drilling and completions parameters and geologic character can all be quantified; providing a common basis for using analytic techniques to predict well performance. The results of these analyses are improved understanding of geologic prospectivity, independent of engineering, as well as indications of optimized engineering techniques for different geologic scenarios.