The Bakken Formation, an unconventional reservoir with very low permeability, is the main production zone in the Williston Basin, ND. Reliable numerical simulation of production performance of this formation requires an accurate description of the rock structures. Characterizing the pore structures is very important in understanding the storage capacity and also the mass transport potential of hydrocarbon. This has been the subject of number of studies by many researchers in the past few years. It has been found that the conventional methods are not applicable to characterize the nano-pore structures of shale formations due to several factors, including low resolution or the most important one, the potential damage to the tight sample during lab testing. This calls for methods which are specifically applicable to characterizing ultra-small pore structures.

In this paper, first we analyze mineral compositions of the samples that are from the Bakken Formation by XRD2. Then we use FESEM to analyze the microstructures of the samples and identify the existence of nano-pores. Then Atomic Force Microscopy (AFM) is acquired for more detailed characterization. We focused to show the great potential of this method in characterizing and quantifying the pore structures in the Bakken Formation. Finally future research work regarding how AFM can provide more insight to the shale nano world are noted.

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