Modeling Fracture Parameters in the Middle Bakken Siltstone

This work is a statistical rock physics method based on well data to explain velocity measurements in the Middle Bakken Siltstone as a function of variable composition, matrix porosity, and fracture porosity. The end goal is to obtain estimates of fracture density along with associated uncertainty within this unit. Production from the Middle Bakken Siltstone results from in situ and induced fractures. Providing locations of higher fracture density from geophysical measurements would allow for optimizing placement of wells in this unconventional reservoir. The method presented here treats the Middle Bakken as an isotropic rock, with randomly oriented fractures. Using the self-consistent approximation, the effective elastic properties are computed as a function of composition, pore and fracture porosity, and aspect ratios of each constituent. By statistically simulating fracture aspect ratios and fracture density, the modelled elastic properties can be related to the fracture density. The result is a distribution of fracture density at each depth interval in a well, which provides the ability to analyse the uncertainty in this parameter.