Abstract
The Montney Formation, a tight unconventional reservoir in Western Canada, has been explored for the past two decades and over the last 10 years has moved towards being a primary exploration target. Qualitative and quantitative petrophysical analysis of the Montney Formation has always been a challenge to researchers. Reservoir characterization is generally hindered by lab-based methods for permeability estimation, proper estimation of the pore size distribution and development of correlations between the rock properties and hydraulic flow.
This report examines results from permeametry, mercury porosimetry, helium pycnometry and scanning electron microscopy (SEM) images performed on 53 samples of the Montney Formation to understand the complicated pore network structure of the rock and study the predictive power of a permeability prediction model.
Pulse-Decay permeability is measured on cores at effective reservoir pressure. Crushed samples are used to obtain mercury capillary pressure, pore size distribution curves, GRI and mercury porosity and matrix permeability. SEM images are used to study pore development and porosity as well as investigating the presence of microfractures. The permeabilities of these samples range from 10 nanodarcies to 0.1 milidarcies and porosities range from 2-10 percent. Due to high surface intrusions in the mercury porosimetry tests, extraction of pore size distributions and capillary pressure curves are problematic and cut-offs are applied based on the derivative of the capillary pressure curve to help understand the complicated pore network of the rock and correlate it with permeability.
This study shows that mercury porosimetry results can be used to categorize the rocks into subcategories for further analysis. Different methods correlating rock properties to permeability are examined. The results specifically indicate that pulse-decay permeability is influenced by over-burden pressure and the presence of microfractures and that the appropriate pore diameter shows consistent correlation with the derivative of the capillary pressure curve.
