The Effect of Pore Morphology on Fracture Systems

ABSTRACT: Hydraulic fracturing is widely applied to oil production from unconventional reservoirs, but the effect of the pore morphology of the reservoir is still poorly understood. Understanding the pore morphology is important to fracture the rock for enhanced oil recovery purposes. Changes in the mineralogy and the texture of the matrix are due to the diagenesis process or chemical activities, where the chemically active minerals during a chemically active fluid injection or diagenetic dolomitization significantly affect the pore system, which in turn affects the propagation of the wave velocity. The effect of the pore morphology on the frackability of the Bakken shale in North Dakota was investigated as part of this study. Different pore morphologies were assigned to the reservoir using the rock physics model Kuster-Toksöz (KT) to estimate the effective bulk and shear moduli, densities, compression (Vp), and shear (Vs) velocities at different pore types. The results showed that all the elastic properties (K, G, Vp, and Vs) increase with respect to the increase of the geometry factor of the pore (aspect ratio). This shows the effect that pore morphology can have on the strength of the reservoir and the ability to generate fractures during a hydraulic fracture simulation. Also, the findings from this study suggest that understanding the pore morphology can improve the ability to increase the oil recovery factor from unconventional reservoirs.