Ping Li's dissertation
by
Ping Li, Ph.D.
University of Texas at Austin, 1997
Supervisor: Ekwere J. Peters
Measurement of the in-situ fluid saturation distributions is essential and
important in laboratory coreflooding experiments in order to correctly evaluate
the fluid displacement mechanisms and processes. Nuclear magnetic resonance
(NMR) imaging has unique advantages for the direct measurement and visualization
of in-situ fluid distributions. There have been some development of NMR imaging
techniques to observe the distributions of fluids in porous media. However, most
of these studies provide only qualitative measurements. Some of the quantitative
methods proposed in the literature have certain limitations in practical
laboratory corefloods. The objective of this research was to develop practical,
quantitative NMR imaging techniques and processing procedures for the direct
measurement and mapping of in-situ fluid saturation (or concentration)
distributions in laboratory coreflooding experiments.
In this study, two practical and quantitative NMR imaging techniques: T1
-weighted, inversion single-spin-echo NMR technique and
Carr-Purcell-Meiboom-Gill (CPMG) multiple-spin-echo NMR technique have been
successfully implemented. The inversion spin-echo technique distinguishes the
water signal from the oil signal via the difference in longitudinal relaxation
times T1 of oil and water, and consequently eliminates the NMR signal
of oil. The CPMG technique distinguishes the water signal from the oil signal by
simultaneously measuring the transverse relaxation times T2 of oil
and water components.
Practical and quantitative image processing procedures have been successfully
developed for the spin-echo and the CPMG NMR techniques. Through these
procedures, the measured NMR signal intensities were converted into in-situ
fluid saturation (or concentration) profiles and saturation (or concentration)
images.
Immiscible and miscible displacement experiments were conducted to validate
the quantitative NMR techniques and the image processing procedures developed in
this study. The results show that the spin-echo and the CPMG NMR techniques and
their image processing procedures can accurately measure and map the in-situ
fluid saturations in porous media in laboratory coreflooding experiments. The
results of this study will find applications in a variety of industrial
processes that involve fluid flow and mass transport in porous media, such as
improved oil and gas recovery and contaminants migration and remediation.
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