Page 8 - Enhanced Oil Recovery in Shale and Tight Reservoirs

Contents vii

8.7 Effect on rock mechanical properties 191
8.8 Further discussions and summary of views and hypotheses 194
8.9 Effect of low-pH and carbonated water 197
8.10 Effect of high-pH water 202
8.11 Cooling effect of injected water 204
8.12 Reaction-induced fractures 205
8.13 Surfactant effects 212

9. EOR mechanisms of wettability alteration and its
comparison with IFT 213
9.1 Introduction 213
9.2 Mechanisms of interfacial tension (IFT) reduction 214
9.3 Mechanisms of wettability alteration on oil recovery 217
9.4 Mathematical treatments of wettability alteration and IFT effect 220
9.5 IFT reduction versus wettability alteration 226
9.6 Specific surfactant EOR mechanisms related to shale and
tight formations 236
9.7 Surfactant selection for wettability alteration 242
9.8 Determination of wettability 253
9.9 Conversion of wetting angles 276
9.10 More on wettability of shale and tight formations 277

10. Spontaneous imbibition 279
10.1 Introduction 279
10.2 Discussion of some theoretical equations on spontaneous imbibition 279
10.3 Effect of permeability and porosity 285
10.4 Effect of initial wettability and wettability alteration 290
10.5 Effect of interfacial tension (IFT) 293
10.6 Effect of diffusion 296
10.7 Effect of gravity 297
10.8 Effect of viscosity ratio 301
10.9 Effect of initial water content 301
10.10 Countercurrent flow versus cocurrent flow 301
10.11 Behaviors of different surfactants 303

11. Forced imbibition 309
11.1 Introduction 309
11.2 Description of a base shale model 310
11.3 Shale rock versus sand rock 315
11.4 Relative permeability change versus capillary pressure change 321
11.5 Effect of capillary pressure 322