Shale Pore Throat Size, Pore Volume, and Pore Size Distribution
Mercury intrusion porosimetry is a valuable method for characterizing relative pore space dimensions. This dynamic technique is based on the intrusion of mercury into a porous structure under stringently controlled pressures. Mercury intrusion porosimetry permits the calculation of numerous sample properties such as pore size distributions, total pore volume, total pore surface area, median pore throat diameter, and sample densities (bulk and skeletal).
Capillary behavior and permeability are critical to reservoir behavior. Porosimetry is among the few techniques capable of probing the fine connected pore space of shales. This method is particularly useful in evaluation reservoir quality variations within a shale play and in petrotyping shale (Kale et al., 2010, Society of Petroleum Engineer).Various empirical transforms can be applied to estimate permeability from mercury intrusion data. While not quantitative, these estimates can provide a relative assessment of the variation in permeability. Mercury intrusion, used in conjunction with pycnometer data, provides estimates of the fraction of pore space that is connected and as such producible. Mercury intrusion also provides information in terms of tortuosity, or the loss of interconnectivity of micro channels under depth conditions, that will lower permeability, as well as gas and water flowability. Combined with gas adsorption data, our instruments can provide the full range of pore size distributions in natural shale samples.