Shale Pore Characterization Using NMR Cryoporometry with Octamethylcyclotetrasiloxane as the Probe Liquid

Abstract

Fluid flow and chemical transport within shale are determined by the pore size distribution and its connectivity. Because of both low porosity and small (nanometer) pore size, common characterization methods, such as mercury injection capillary pressure (MICP) and the nitrogen adsorption method (NAM), have limited resolution and applicability. Nuclear magnetic resonance cryoporometry (NMR-C) is a novel characterization method that exploits the Gibbs–Thomson effect and provides a complementary method of characterizing aggregate pore structure at fine resolution. We use water and octamethylcyclotetrasiloxane (OMCTS) as probe liquids for NMR-C on controlled porosity samples of SBA, CPG, and shale. The analysis accommodates the influence of melting temperature, KGT, and surface layer thickness, e, on the pore size distribution (PSD). Calibration experiments permeated with the two fluids demonstrate that OMCTS has a larger KGT and that the PSD for different cryoporometric materials is not subject to different ...