On the Characterization of Bakken Formation: Oscillating-Pulse, Pulse-Decay Permeability Measurement & Geomeachanics

With the development of horizontal drilling and hydraulic fracturing in recent years, unconventional formations, such as the Bakken have come into the foreground of the oil and gas industry. However, due to its heterogeneity and ultra-low permeability and porosity, the Bakken recovery factors remain low (5%-10%). Complexity associated with the characterization of tight shale plays and rock/fluid interactions is multifold. One of the critical challenges is the description of rock structures and characterizing it to understand permeability, geomechanics, storage capacity, and fluids transport. The measurement of permeability of Bakken rock samples is very challenging due to their extremely low permeability. In this study, we investigate the permeability of a number of Bakken core samples using oscillating-pulse and pulse-decay methods and then compare them with the steady-state measurements. Also, the elastic moduli (i.e. Young's modulus, Poisson's ratio) of these core plugs were estimated through the measurement of seismic velocities (V_p and V_s). The results from this study confirmed that the pulse-decay permeability measurement could yield reliable results when compared to other methods. Accurate characterization of Bakken core samples can enhance our knowledge of fluid flow and CO₂-EOR potentials in the Williston Basin, ND.