Determining NMR flow propagator moments in porous rocks without the influence of relaxation.
Flow propagators, used for the study of advective motion of brine solution in porous carbonate and sandstone rocks, have been obtained without the influence of Nuclear Magnetic Resonance (NMR) relaxation times, T1 and T2. These spin relaxation mechanisms normally result in a loss of signal that varies depending on the displacement zeta of the flowing spins, thereby preventing the acquisition of quantitative propagator data. The full relaxation behaviour of the system under flow needs to be characterised to enable the implementation of a true quantitative measurement. Two-dimensional NMR correlations of zeta-T2 and T1-T2 are used in combination to provide the flow propagators without relaxation weighting. T1-zeta correlations cannot be used due to the loss of T1 information during the displacement observation time Delta. Here the moments of the propagators are extracted by statistical analysis of the full propagator shape. The measured displacements (first moments) are seen to correlate with the expected mean displacements for long observation times Delta. The higher order moments of the propagators determined by this method indicate those obtained previously using a correction were overestimated.
Department of Chemical Engineering, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, UK.
J
J
Mitchell
D A
DA
Graf von der Schulenburg
D J
DJ
Holland
E J
EJ
Fordham
M L
ML
Johns
L F
LF
Gladden
D000465:Algorithms; D004058:Diffusion; D019015:Geologic Sediments / Q000032:analysis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D012212:Rheology / Q000379:methods*; D012492:Salts / Q000032:analysis* / Q000737:chemistry*
D012492:Salts; C017082:brine