QUANTIFYING THE EFFECTIVE POROSITY OF RESERVOIR AND SOURCE ROCKS

Microscopic pore structure characteristics of both reservoir and source rocks (e.g., sandstones, carbonates, and mudrocks) –pore-size distribution, pore shape, and pore connectivity – control fluid flow and hydrocarbon movement. Focusing on effective porosity, the portion of connected pore space as conductive pathways to participate in flow and movement (f_e / f,, as an indicator of macroscopic connectivity), this presentation discusses various approaches to quantifying the effective porosity for a range of oil and gas reservoir and source rocks. The approaches include pycnometry (liquid and gas), pore and bulk volume measurement after vacuum saturation, porosimetry (mercury intrusion porosimetry, low-pressure gas physisorption isotherm, water vapor adsorption/desorption isotherm, nuclear magnetic resonance cyroporometry), imaging (X-ray computed tomography, Wood’s metal impregnation, field emission-scanning electron microscopy SEM, focus ion beam-SEM), scattering (ultra- and small-angle neutron), the utility of both hydrophilic and hydrophobic fluids as well as fluid invasion tests (imbibition, diffusion, vacuum saturation) followed by laser ablation-inductively coupled plasma-mass spectrometry imaging of different nm-sized tracers. Our results indicate a disparate characteristics and range of effective porosity, with a single-zone behavior and a value of connectivity at approximately 70% for sandstones, as compared to “dual-connectivity zones” at 70% and 0.01% for mudrocks.