1.
n. [Formation Evaluation]
The rapid rate of
diffusion of molecules in
pore fluids during a
nuclear magnetic resonance (
NMR) measurement. In fast diffusion, the hydrogen within a certain volume diffuses fast enough that only one
T2 peak is observed for the whole volume. This is the case in a single pore, because the surface relaxation is not strong enough for observation of separate T
2 peaks, for example, for water near the surface of a grain and water in the middle of the pore. Fast diffusion is also considered to occur between most
clay- and capillary-
bound water, between normal pores and micropores within some carbonates, and in some other systems.