Cherian, Bilu Verghis (Schlumberger) | Stacey, Edwin S. (Petro-Hunt LLC) | Lewis, Ray (Petro-Hunt LLC) | Iwere, Fabian Oritsebemigho (Schlumberger) | Heim, Robin Noel (Schlumberger) | Higgins, Shannon Marie (Schlumberger)
In field development programs where large variations in reservoir and completion parameters exist, the evaluation of reservoir performance to determine the optimal completion strategy can be a challenging task. This paper presents findings from a recent integrated cross-discipline analysis of a pilot program performed in the Bakken and Three Forks Formations (Williston Basin, North Dakota) to evaluate the impact of petrophysical and geomechanical properties on hydraulic fracture lengths, reservoir connectivity, well performance and well spacing.
Microseismic, geological, geomechanical, completions, engineering and production data were integrated in single and multi-well modeling approaches to provide an objective method to evaluate and compare well performance. Results and conclusions from various disciplines were validated by integrating operational observations with the modeling. The application of the proposed workflow allows one to (1) understand and evaluate the effect of fracturing parameters (length/conductivity) on well performance, (2) characterize reservoir and fracture properties using hydraulic fracture pressure and production history matching techniques (3) relate fracture parameters to reservoir, geology and mechanical properties and, (4) provide a methodology to understand key drivers controlling the development strategy of an asset.
The Bakken Formation is a widespread unit in the central and deeper portions of the Williston Basin in the states of Montana and North Dakota, in the United States, and the provinces of Saskatchewan and Manitoba in Canada (Figure 1). The formation is comprised of an Upper Shale Member, a Middle Siltstone Member and a Lower Shale Member (Figure 2). The Upper and Lower Bakken shales are organic rich and are the petroleum source rocks for both the Bakken and Three Forks Formations. Porosity in the middle member of the Bakken formation is in the range of 4% to 9%, and water saturation ranges between 25% and 50%, depending upon the county where wells are located. In the Williston Basin the Upper Bakken Shale is overlain by the Lodgepole Formation which consists of dense, dark gray to brownish gray limestone and gray calcareous shale. Below the Lower Bakken Shale is the Three Forks formation. The Three Forks is composed of thinly interbedded greenish gray and reddish brown shales, light brown to yellow gray dolostone, gray to brown siltstone, quartzose sandstone and minor occurrences of anhydrite (Kume, 1963). The contact between the Bakken and Three Forks appears conformable in the deeper portions of the basin and unconformable on the basin flanks. The Three Forks has an average of 30.5 ft pay thickness, 65% oil saturation and 6.9% porosity. The Nisku (or Birdbear Formation) is conformably overlain by the Three Forks Group.