Untitled - Technische Universiteit Eindhoven

More documents

Recommendations

Info

6.2. Experimental section 79increasing echo time, gradient strength, diffusion coefficient and gyromagnetic ratio.In a porous material the presence of paramagnetic impurities or internal magneticgradients has little effect on the relaxation of D 2 O compared to H 2 O. Moreover, the useof D 2 O instead of H 2 O allows for a clear separation between the oleic phase (containing1 H) and the aqueous phase. For these reasons, the use of D 2 O is preferred, despite therelatively weak NMR signal of deuterium [122].As for the intrinsic relaxation of the fluids and gels, the relaxation of hydrogen in bulkmixtures, such as TMOS/oil, was discussed in Chapter 2. The relaxation of the deuteriumatoms in the silica gels, prepared with D 2 O, is due to intra-molecular quadrupoleinteraction [41], and is sensitive to the mobility of the molecules. T 2 is shorter for the gelsthan for bulk D 2 O. In gelling solutions, T 2 is initially similar to that of bulk D 2 O, but itbecomes shorter in the course of time and reaches a plateau at the gel time. The finalreduction in T 2 increases with increasing initial TMOS content of the gelling solution.The main contribution to the reduction in T 2 is due to the interaction (e.g. adsorption)of the D 2 O molecules with the silica network.6.2 Experimental section6.2.1 Materials and methodsTetra-methyl-ortho-silicate, Si(OCH 3 ) 4 , was obtained from Aldrich (>99% pure). It wasdissolved in Isopar V, a mineral oil with a viscosity of 10 mPa s at room temperature,obtained from ExxonMobil. The volume fraction of TMOS in oil was always equal to0.20. For the aqueous phase we used D 2 O (CIL, Andover, MA, 99.9% pure). In addition,three different D 2 O buffers were prepared by adding salts and chemicals containing normalhydrogen in little amounts. The pH was measured with a semiconductor type pH meter.The low pH buffer (pH = 2.84) contained 8.47 g of citric acid, 3.22 g of NaOH and 2.18g of HCl per liter, the intermediate pH buffer (pH = 6.2) contained 12.53 g of citric acidand 6.32 g of NaOH per liter, and the high pH buffer (pH = 9.48) contained 3.81 g ofdi-sodiumtetraborat per liter. The pH of the untreated D 2 O was around 5.5. The slightdegree of acidity is attributed to solution of CO 2 from the atmosphere.Bentheim sandstone cores with a diameter of 16 mm were cast into an impermeableepoxy layer, thereby increasing the diameter to 20 mm. The penetration of the epoxy inthe core varied between 1 and 2 mm. The length of the cores is 60 mm. The porosity of asample was determined through a mercury intrusion porosity (MIP) measurement yieldinga porosity of 0.22 and a mean pore size of 33 ± 10 µm. In addition, a Bentheim corewas scanned with a micro-CT (X-ray computer tomography) apparatus (Scanco Medical,type VivaCT 40) with a resolution of 10.5 × 10.5 × 10.5 µm 3 . An example image is givenin Figure 6.2. The image clearly shows the irregular structure of the pore space, and thatthe rock contains a few pores with a size much greater than 33 µm . The pore volume ofeach core is about 2 ml. Bentheim is a water-wet rock, consisting mainly of quartz andlittle amounts of non-swelling clay (less than 1%, see Chapter 7).
80 6. Coupled mass transfer and gelation of TMOS in porous materials1011Y [mm]1213143 4 5 6 7 8 9X [mm]Fig. 6.2: Micro-CT image of Bentheim sandstone showing the pore structure (black) and thesolid material of a slice wih a thickness of 10.5 µm.effluentoutletz = L/225 mm12.5 mmepoxy∆Pz0 mmz = -L/2-12.5 mm-25 mmcorepump 1oilpump 2waterinletFig. 6.3: Schematic view of core holder and fluid injection set-up. The length L is 60 mm. Thefluids are injected by either pump 1 (for oil and oil/TMOS) or pump 2 (for water).The differential pressure ∆P over the core is measured with a differential pressuretransducer connected to the tubing. The dashed lines indicate the slice positions inthe NMR measurements.
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: 28 2. Coupled mass transfer and sol
Page 39 and 40: 30 2. Coupled mass transfer and sol
Page 41 and 42: 32 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: 78 6. Coupled mass transfer and gel
Page 91 and 92: 82 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 139 and 140:
130 8. Model of reactive transport
Page 141 and 142:
132 9. Concluding remarks and outlo
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
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

Create successful ePaper yourself

Delete template?

Save as template?