Chapter 3
2) The surface relaxivity (p) and the bulk relaxivity (1∕T2,b∪∣k) of the drop
phase are known. T2,bulk can be easily measured from a CPMG
experiment on a bulk sample of the drop phase.
3) T2,bulk for the dispersed phase is indeed single-valued and not a
distribution of characteristic bulk relaxation times.
4) Two independent sets of T2j,∙ - fi values can be resolved from the T2
distribution of the emulsion for the oil and water phases, respectively.
The minimum and maximum drop sizes that can be determined via CPMG
are, respectively[5]:
⅛in ≈ 6∕‰ - ⅛ax ≈ min{T> / 2p, 2SNRpT^bulk / e} [3.7]
Here T2,min is the smallest T2 of water drops measured by CMPG. SNR is
signal to noise ratio of the measurement. D is diffusivity of dispersed phase.
Using the data reported in reference [5], the drop size range which can be
measured by CPMG is 16 nm to 580 μm [5].
But in some cases, such as water in light oil emulsion, T2 distribution of
dispersed water phase is very close to that of continuous oil phase. Thus CPMG
method is not appropriate because the T2 distribution is not distinguishable. The
alternative methods for estimating the water fraction and drop size distribution will
be discussed in the following sections.
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