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SUMMARY:Diffusion problems for Nuclear Magnetic Relaxation in permeable po
 rous media - Edmund Fordham\, Energetics Research
DTSTART:20190131T113000Z
DTEND:20190131T123000Z
UID:TALK117166@talks.cam.ac.uk
CONTACT:Catherine Pearson
DESCRIPTION:NMR is now a well-established petrophysical measurement in pet
 roleum\nwell-logging and in surface core analysis. Brownian diffusion of\n
 fluid molecules within the pore space\, subject to partially\nabsorbing bo
 undary conditions at the pore surface\, is fundamental to\ninterpretation 
 of experimentally observable relaxation measurements.\nThe archetype for i
 nterpretations in practical petrophysics remains\nthat of an isolated pore
 \, in the so-called fast diffusion regime\, a\ncorrect limiting case but i
 nsufficient for several more complicated\ncontexts commonly encountered in
  practice. Interesting analytical\nproblems arise in the development of mo
 dels which go beyond the\narchetype. We shall discuss two developments: (1
 ) an analytical\napproach to a coupled diffusion problem for microporous r
 ock\ntextures where large and much smaller pores are closely adjacent (2)\
 nthe extensions required where local contrasts in magnetic\nsusceptibility
  cannot be neglected.\nThe former topic addresses measured responses found
  in at least two\npractical contexts where the “isolated pore” model c
 annot be\nsustained: (a) carbonate grainstone textures typical of many\noi
 l-bearing formations in the Middle East (b) compacts made of\nkerogen isol
 ates in current research on the NMR of\nhydrocarbon-bearing shales. The la
 tter topic addresses measured\nresponses in systems (typically sandstones)
  where induced internal\nmagnetic field gradients require extensions to th
 e governing\ndiffusion equation\, with analytical difficulties only partia
 lly\nsolved. Implications for MRI will be discussed.\n
LOCATION:Open Plan Area\, BP Institute\, Madingley Rise CB3 0EZ
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