PFG NMR time-dependent diffusion coefficient analysis of confined emulsion: post drainage phase conformation

TL;DR

This study uses PFG NMR to analyze how water and oil phases configure within porous glass beads after drainage, revealing changes in surface-to-volume ratio and fluid conformation, including droplet formation.

Contribution

It introduces a novel application of time-dependent diffusion coefficient analysis to characterize post-drainage fluid configurations in porous media.

Findings

Surface-to-volume ratio increases after drainage.

Bi-Gaussian model effectively describes fluid conformation.

Droplet formation within pores is supported by diffusion data.

Abstract

In this work, we present a characterization of phase configuration in water-saturated sintered glass bead samples after oil injection, through the analysis of time-dependent diffusion coefficients obtained from sets of one-dimensional pulsed field gradient nuclear magnetic resonance (PFG NMR) measurements, pre and post drainage. Estimates of samples surface-to-volume ratio and permeability from pre drainage PFG measurements in a water-saturated sample were compared with analytical and reported values, respectively, and a fair agreement was found in both cases. Short-time analysis of diffusion coefficients extracted from PFG measurements was used to quantify the increase in surface-to-volume ratio probed by the wetting phase after drainage. Analysis of water and oil diffusion coefficients from post drainage PFG experiments were carried out using a bi-Gaussian model, and two distinct scenarios were considered to describe fluids conformation within pores. For the case where non-wetting phase was considered to exhibit a poorly connected geometry, an analysis assuming the formation of oi-in-water droplets within pores was performed, and a Gaussian distribution of droplets radii was determined.