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AAPG Rocky Mountain Section Meeting

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Geologic Modelling of Unconventional Field Using Geostatistics, Williston Basin, North Dakota

Abstract

The geological model of the unconventional shale Bakken formation has been built using geostatistical methods and approach. Variograms were constructed in order to achieve an accurate interpolation between the data from the given wells. Stochastic method, like the Sequential Gaussian Simulation, was used to populate the model with reservoir properties. Petrophysical analysis of this field was done previously using the well log analysis with commercial software, and the resulting well log curves were imported into geomodelling software. Once the model has been constructed, the trends and the better zones could be seen and identified. The area is known to have a geological trend in the northwestern direction, and it was confirmed by the model and was seen in the distributions from several properties. A total of 5 models of petrophysical properties were constructed – porosity, permeability, effective porosity, water saturation, shale volume. Variogram maps were built to see the anisotropy direction; it followed the geological trend mentioned. Geomodelling is the important step in reservoir development, since by looking at the distribution of the reservoir properties the engineers can identify the spots that require further development. The findings found during this case study could be tried in different unconventional plays around the world. This work will serve future researchers as the reliable data point in the reservoir studies. It will add to the pool of knowledge about the Bakken and how its properties are distributed which in turn can help the oil companies identify well placement locations for exploration.