Untitled - Technische Universiteit Eindhoven

More documents

Recommendations

Info

6.3. Results and discussion 910.250.2A03. No bufferA05. pH = 2.84A07. pH = 6.20A09. pH = 9.480.15φ T0.10.0500 2 4 6 8 10time [h]Fig. 6.10: Concentration of TMOS in the oleic phase, φ T , as a function of time and averagedover all slices. The profiles were smoothed but not corrected for the effect of hydrogenpresent in the aqueous phase. The experiments were done at 25 ◦ C and the pH ofthe aqueous phase was varied (see Legend).of hydrolysis. At the lowest pH the rate of hydrolysis is the highest, and therefore themass transfer is the fastest. The lowest values for α T are found for the unbuffered and pH= 6.20 systems. It is noted that the pH of the aqueous phase in the unbuffered systemsdecreases to an unknown extent as the hydrolysis of TMOS proceeds. At 50 ◦ C the masstransfer rate is increased roughly by a factor 2 in case of the unbuffered and pH = 6.20systems. For the pH = 9.48 system α T increased by a factor 4 to 2.9 ± 0.3 h −1 . For thepH = 2.84 system (A06) the mass transfer was already completed within the dead time ofthe experiment, so that α T > 20 h −1 . Exact quantitative comparison between the masstransfer results of the core experiments and the bulk experiments are not made due tothe different spatial distribution and ratio of the liquid phases. However, like in the bulk(see Chapter 4) the mass transfer is predominantly driven by the hydrolysis reaction, therate of which is strongly dependent on the pH of the aqueous phase, and on temperature,especially for the alkaline systems. In the acid-catalyzed system, with a pH around 3, thehydrolysis rate and the mass transfer rate are the fastest, like in the bulk experiments.At a pH of about 6, the hydrolysis rate should be minimum [33]. The mass transfer ratesat a pH of 6.20 in the core experiments are similar to those for the unbuffered system,however, in the bulk it was found that the mass transfer was much faster in the unbufferedsystems compared to the buffered systems at a pH of 5.5.
92 6. Coupled mass transfer and gelation of TMOS in porous materials0.150.1z = -25 mmz = -12.5 mmz = 0 mmz = 12.5 mmz = 25 mmT 2,AV[s]0.0500 2 4 6 8 10time [h]Fig. 6.11: Weighted-mean transverse relaxation time T 2,AV of the 2 H content in the aqueousphase measured during shut-in (step 5b) in five different slices of the core in experimentA03.6.3.4 GelationResults of experiment A03The measurement of the transverse relaxation behavior in the aqueous phase during shutin(step 5b) in experiment A03 is discussed in this section. The continuous measurementof T 2 of the 2 H content in the five slices was started within three minutes after the injectionstep. The spin echo trains, acquired with the CPMG sequence, were inverted with theCONTIN routine. Again, the weighted-mean T 2 as defined in Eq. 6.1 was used tocharacterize the average T 2 within each slice as a function of time. The results are shownin Figure 6.11 for the first 10 hours of the experiment. Between each measured slice thetotal delay time is about 5 minutes. As a consequence, the first data point in the fifthslice (z = 25.0 mm) was acquired half an hour after the injection was ended. The firstdata point in the first slice is found at T 2,AV = 0.123 s. The remaining values of T 2,AV inthe other slices and for the other time steps drop progressively to about 0.025 s.The drop in T 2,AV is due to the reaction of TMOS with the water molecules, i.e. dueto the formation of methanol and due to the cross-linking silica aggregates. The effect ofthe gel reaction dominates the shortening of T 2,AV , compared to the effect of the surfacerelaxivity of the rock. However, the exact pore-scale distribution of the reacting TMOSand formed gel in the aqueous phase remains unclear, and the weighted-mean T 2 can onlyindicate an effective reaction rate and effective gel transition time. Based on the ratioof oil and water (derived from S w ≈ 0.25) and the initial concentration of TMOS (φ T (0)= 0.20), the final volume fraction of TMOS in the aqueous phase, assuming full masstransfer, is 38%. It was found in bulk experiments that at this concentration the resultinggel always percolated into a macroscopic gel for all buffers used. On the pore scale the
Page 2:
TWO-PHASE REACTIVE TRANSPORTOF AN O
Page 5 and 6:
Dit proefschrift is goedgekeurd doo
Page 7 and 8:
4. The effect of pH on mass transfe
Page 9 and 10:
Samenvatting . . . . . . . . . . .
Page 11 and 12:
2 1. Introductionproducerbarrierlow
Page 13 and 14:
4 1. IntroductionTwo inter-European
Page 16:
Part ITwo-phase bulk systems7
Page 19 and 20:
10 2. Coupled mass transfer and sol
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
32 3. Interfacial effects during re
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50: 40 3. Interfacial effects during re
Page 51 and 52: 42 3. Interfacial effects during re
Page 53 and 54: 0+,44 4. The effect of pH on mass t
Page 55 and 56: 46 4. The effect of pH on mass tran
Page 67 and 68: 58 5. Cross-linking of silica with
Page 71 and 72: 0+,62 5. Cross-linking of silica wi
Page 84: Part IIGel placement in porous mate
Page 87 and 88: 78 6. Coupled mass transfer and gel
Page 99: 90 6. Coupled mass transfer and gel
Page 107 and 108: 98 7. Permeability reduction in por
Page 109 and 110: 100 7. Permeability reduction in po
Page 123 and 124: 114 8. Model of reactive transport
Page 141 and 142: 132 9. Concluding remarks and outlo
Page 149 and 150: 140
Page 151 and 152:
-142 Appendix A, - C D *, - D
Page 153 and 154:
144 Appendix Awhere S 0 is a consta
Page 155 and 156:
146 Appendix AThe 0.95 Tesla scanne
Page 157 and 158:
148 Appendix B
Page 159 and 160:
150 Appendix CwhereΩ A (θ) = −2
Page 161 and 162:
152 Appendix C
Page 163 and 164:
154 Appendix D
Page 165 and 166:
156 Appendix Eand equal to zero in
Page 167 and 168:
158 Appendix EAs the saturations, d
Page 169 and 170:
160 Bibliography[12] B. Vinot, R. S
Page 171 and 172:
162 Bibliography[40] M. D. Mantle a
Page 173 and 174:
164 Bibliography[70] F. J. M. van d
Page 175 and 176:
166 Bibliography[97] K. Yoshida, A.
Page 177 and 178:
168 Bibliography[127] G. W. Scherer
Page 179 and 180:
170 Bibliography
Page 181 and 182:
172 Summaryand gelation rates. The
Page 183 and 184:
174 Samenvattingwaterfase. De T 1 v
Page 185 and 186:
176 List of publications
Page 187 and 188:
178 Dankwoordimmer opgewekte stemmi
Page 189:
Prior to the speech, Harald Cramér
show all

Untitled - Technische Universiteit Eindhoven

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?