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88 6. Coupled mass transfer and gelation of TMOS in porous materials0.20.16z = -25 mmz = -12.5 mmz = 0 mmz = 12.5 mmz = 25 mm0.12φ T[-]0.080.0400 2 4 6 8 10time [h]Fig. 6.8: Derived concentration of TMOS in the oleic phase, φ T , in five different slices of thecore in experiment A03 during shut-in (step 5b). The concentration is based on theaverage T 1 of the total 1 H content and is therefore affected by the presence of hydrogenin the aqueous phase.first slice. This can be explained by assuming that the mixture may not have completelydisplaced the existing oil during placement, despite the injection of 2 PV of mixture.After the initial 10 hours, the T 1 in all slices becomes nearly constant around T 1 = 0.223± 0.006 s, up to the total measurement time of 39 hours.Due to the mass transfer of TMOS from the oleic to the aqueous phase, part of the total1 H content, carried by the TMOS molecules, transfers accordingly between both phases.The saturation recovery sequence measures the recovery of the longitudinal magnetizationof all 1 H atoms in the liquid phases. As long as the fraction of 1 H is low in the aqueousphase, which is the case at the beginning of the shut-in process, the acquired T 1 representsthe effective T 1 of the TMOS/oil phase and the concentration φ T can be determined usingthe calibration results for the bulk mixtures. Direct determination of φ T in the five slicesusing the calibration of T 1 of the oil/TMOS mixtures yields the concentration profilesshown in Figure 6.8.Effect of hydrogen in aqueous phase on determination of φ TAs the TMOS progressively transfers to the aqueous phase, the 1 H content in waterincreases. The measured T 1 is a weighted average of the T 1 of the various species containinghydrogen. The longitudinal magnetization M z (t) can be described by(M z (t) = M 0[1 − f exp − t )(− (1 − f) exp −t )], (6.2)T 1,o T 1,w