Using NMR displacement measurements to probe CO2 entrapment in porous media

Abstract

in Wiley Online Library (wileyonlinelibrary.com).Carbon dioxide sequestration in aquifers is seen as a potential climate change mitigation technique. One physical mechanism by which this could occur is capillary trapping of discrete pore-scale CO 2 bubbles (referred to as ganglia) in the pore space. Nuclear magnetic resonance (NMR) techniques were used to quantify the spatial distribution and pore environment of such CO 2 entrapment in a model porous medium (random glass bead packing). 3D images revealed a relatively macroscopically homogeneous CO 2 entrapment, even though the image resolution is insufficient to resolve individual CO 2 ganglia. Quantification of the pore environment of the CO 2 ganglia was achieved using NMR displacement propagators (displacement probability distributions), acquired both before and after CO 2 entrapment. Lattice Boltzmann (LB) simulations were used to facilitate interpretation of the propagator statistics by considering various pore environments in which CO 2 could become trapped. Comparison with the experimental data suggests that CO 2 is preferentially entrapped in comparatively larger pores.

Pore Scale Processes Associated with Subsurface CO2 Injection and Sequestration

“…The relaxation time of the NMR signal was evidently shortened by the porous material surfaces and CO 2 dissolution. Hussain et al (2011) used NMR techniques to quantify the spatial distribution and pore environment associated with CO 2 capillary trapping in a model porous medium (random glass bead packing). 3D images revealed relatively homogeneous (at Figure 14. XCMT images of A) the pre-experiment silica (dark grey, or purple in the original reference) and calcite (light grey, or yellow in the original reference) sand distribution, clearly visible from the density contrast between the two minerals, B) the distribution of nitrogen, and C) the distribution of scCO 2 .…”

NMR study comparing capillary trapping in Berea sandstone of air, carbon dioxide, and supercritical carbon dioxide after imbibition of water

“…Previous work has used MRI to look at rate of displacement of the front associated with supercritical CO 2 displacement processes in a model glass bead pack [ Liu et al ., ]. An earlier study looked at the transport properties of atmospheric carbonated brine as it flowed through a sandstone rock core [ Hussain et al ., ]. This study extends these applications by looking at the water when supercritical CO 2 is flowing in a water saturated sandstone rock core.…”

Acquisition of spatially-resolved displacement propagators using compressed sensing APGSTE-RARE MRI

“…However, the significantly faster data acquisition times characterising a velocity measurement have resulted in the widespread use of spatially-resolved velocity measurements [2], whilst propagators are usually acquired without spatial resolution. Such spatially-unresolved propagator measurements have been used widely in chemical engineering [3][4][5][6] and petrophysical [7][8][9][10] applications, mainly to study flow dispersion.…”