Table Of ContentENHANCED OIL RECOVERY
IN
SHALE AND TIGHT RESERVOIRS
JAMES J. SHENG
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Contents
Acknowledgments ix
1. Introduction to shaleand tight reservoirs 1
1.1 Introduction 1
1.2 Definitionsofshaleandtightreservoirs 2
1.3 Shaleandtightresources 6
1.4 Currentproductiontechnologies 6
2. Huff-n-puff gas injection in oilreservoirs 7
2.1 Introduction 7
2.2 Initialsimulationstudiesofhuff-n-puffgasinjection 8
2.3 Experimentalmethods 9
2.4 Effectofcoresize 18
2.5 Effectsofpressureandpressuredepletionrate 20
2.6 Effectofsoakingtime 25
2.7 EORperformancewithnumberofcycles 29
2.8 Effectofinjectedgascomposition 31
2.9 Minimummisciblepressure 37
2.10 Effectofdiffusion 41
2.11 Effectofwatersaturation 43
2.12 Effectofstress-dependentpermeability 45
2.13 Huff-n-puffmechanisms 46
2.14 Gaspenetrationdepth 51
2.15 Fieldprojects 54
3. Asphalteneprecipitationanddepositioninahuff-n-puffprocess 61
3.1 Introduction 61
3.2 Experimentsofasphalteneprecipitationandpermeabilityreduction 61
3.3 Depositionmechanisms 69
3.4 Numericalanalysis 71
3.5 Effectofasphaltenedepositiononhuff-n-puffoptimization 75
4. Huff-n-puff injection in shale gas condensate reservoirs 81
4.1 Introduction 81
4.2 Experimentalsetup 83
4.3 Huff-n-puffgasinjection 84
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4.4 Huff-n-puffversusgasflooding 86
4.5 Core-scalemodelingofgasandsolventperformance 91
4.6 Reservoir-scalemodelingofgasandsolventperformance 98
4.7 Afieldcaseofmethanolinjection 101
4.8 Surfactanttreatment 102
4.9 Factorsthataffecthuff-n-puffgasinjectionperformance 105
4.10 Optimizationofhuff-n-puffinjection 109
4.11 Mechanismsofhuff-n-puffinjection 110
5. Optimization ofhuff-n-puff gas injection in shale and tight
oilreservoirs 117
5.1 Introduction 117
5.2 Setupofabasesimulationmodel 118
5.3 Optimizationprinciples 121
5.4 Optimizationcriteria 122
6. Gasflooding compared with huff-n-puffgas injection 133
6.1 Introduction 133
6.2 Researchresultsongasflooding 133
6.3 Gasfloodingversushuff-n-puffgasinjection 137
6.4 Fieldapplicationsofgasflooding 145
6.5 Feasibilityofgasflooding 149
7. Water injection 151
7.1 Introduction 151
7.2 Waterflooding 151
7.3 Waterhuff-n-puffinjection 156
7.4 Waterfloodingversushuff-n-puffwaterinjection 162
7.5 Waterinjectionversusgasinjection 162
7.6 Water-alternating-gas(WAG) 166
7.7 Huff-n-puffwaterandsurfactantinjection 166
7.8 WaterinjectioninChina 167
8. Fluid-rock interactions 173
8.1 Introduction 173
8.2 Evidencesofmicrofracturesgeneratedorexistingnatural
fracturesreopened 173
8.3 Effectofconfiningstress 179
8.4 Effectofbedding 186
8.5 Effectofexistingnaturalfractures 186
8.6 Permeabilitychangesfromwater-rockinteractions 187
Contents vii
8.7 Effectonrockmechanicalproperties 191
8.8 Furtherdiscussionsandsummaryofviewsandhypotheses 194
8.9 Effectoflow-pHandcarbonatedwater 197
8.10 Effectofhigh-pHwater 202
8.11 Coolingeffectofinjectedwater 204
8.12 Reaction-inducedfractures 205
8.13 Surfactanteffects 212
9. EOR mechanismsof wettability alteration and its
comparison with IFT 213
9.1 Introduction 213
9.2 Mechanismsofinterfacialtension(IFT)reduction 214
9.3 Mechanismsofwettabilityalterationonoilrecovery 217
9.4 MathematicaltreatmentsofwettabilityalterationandIFTeffect 220
9.5 IFTreductionversuswettabilityalteration 226
9.6 SpecificsurfactantEORmechanismsrelatedtoshaleand
tightformations 236
9.7 Surfactantselectionforwettabilityalteration 242
9.8 Determinationofwettability 253
9.9 Conversionofwettingangles 276
9.10 Moreonwettabilityofshaleandtightformations 277
10. Spontaneous imbibition 279
10.1 Introduction 279
10.2 Discussionofsometheoreticalequationsonspontaneousimbibition 279
10.3 Effectofpermeabilityandporosity 285
10.4 Effectofinitialwettabilityandwettabilityalteration 290
10.5 Effectofinterfacialtension(IFT) 293
10.6 Effectofdiffusion 296
10.7 Effectofgravity 297
10.8 Effectofviscosityratio 301
10.9 Effectofinitialwatercontent 301
10.10 Countercurrentflowversuscocurrentflow 301
10.11 Behaviorsofdifferentsurfactants 303
11. Forced imbibition 309
11.1 Introduction 309
11.2 Descriptionofabaseshalemodel 310
11.3 Shalerockversussandrock 315
11.4 Relativepermeabilitychangeversuscapillarypressurechange 321
11.5 Effectofcapillarypressure 322
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11.6 Effectofpressuregradient(injectionrate) 326
11.7 Experimentalstudyofforcedimbibition 331
11.8 FieldtestsofsurfactantEOR 336
12. Fracturing fluidflow back 339
12.1 Introduction 339
12.2 Fieldobservationsandexperimentalresultsonflowback 341
12.3 Proposedmechanismsoflowflowback 345
12.4 Effectofshut-intimeonflowback 359
12.5 Shut-intimeeffectonfractureconductivity 375
12.6 Effectofinitialwettabilityonflowback 379
12.7 Effectofinvasiondepthonflowbackefficiencyandlatetimeoilrate 385
12.8 Effectofsurfactantsonflowback 390
12.9 Solutionstodealwithflowback 395
13. Air injection 401
13.1 Introduction 401
13.2 Laboratoryexperimentalfacilities 402
13.3 Kineticparameters 407
13.4 Oxidationreactions 427
13.5 Spontaneousignition 435
13.6 Oxygenconsumptionrateinlow-temperatureoxidation 452
13.7 Minimumoilcontentforcombustion 453
13.8 Airrequirementincombustion 453
13.9 EORmechanismsandEORpotentialinshaleandtightreservoirs 454
14. Other enhancedoil recoverymethods 457
14.1 Introduction 457
14.2 Sequentialmethodofhuff-n-puffCO injectionand
2
surfactant-assistedspontaneousimbibition 457
14.3 Chemicalblends 458
14.4 Airfoamdrive 460
14.5 Branchedfractures 461
14.6 Zipperfracture 462
14.7 Refracturing 463
14.8 Diversiontechnologyinfracturing 463
14.9 Energizedfluids 464
14.10 Thermalrecovery 464
14.11 MicrobialEOR 467
Nomenclature 469
References 475
Index 513
Acknowledgments
This book summarizes some of my research results about shale EOR
technologies in the past decade. Some of the dissertation or research work
from my ex-PhD students, ex-postdoctoral students, and current PhD
studentsisusedandcitedtosupport myviewsinthisbook.Theyare Yang
Yu, Lei Li, Ziqi Shen, Siyuan Huang, Yao Zhang, Sharanya Sharma,
Xingbang Meng, Nur Wijaya, Srikanth Tangirala, Tao Wan, Samiha
Morsy,ShifengZhang,HuJia,JunrongLiu,TalalDaouGamadi,andJiawei
Tu. Some of the work published by other authors is cited. Their work is
sincerely acknowledged.
Ihavedevotedmuchofmytimetomycareerdevelopment.Iowemuch
tomywifeYingZhang,mydaughtersEmilyandSelena,andmyparentsJifa
Sheng and Shouying Liu. If my life could be rechosen, I would have
reallocated my time to them.
Some of the research work was supported by the US department of
Energy under Award Number DE-FE0024311, Apache Corporation, and
ConocoPhillips.
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