corrosive species and scaling in wells at olkaria ... - Orkustofnun
corrosive species and scaling in wells at olkaria ... - Orkustofnun corrosive species and scaling in wells at olkaria ... - Orkustofnun
TABLE OF CONTENTS Page 1. INTRODUCTION ................................................................................................................... 1 1.1 Corrosion in geothermal environments.......................................................................... 1 1.2 Scale formation.............................................................................................................. 2 1.2.1 Silica................................................................................................................ 2 1.2.2 Calcite.............................................................................................................. 4 1.2.3 Other scales ..................................................................................................... 4 1.2.4 Objectives of study .......................................................................................... 5 2. GEOLOGICAL FEATURES OF THE STUDY AREA.......................................................... 6 2.1 The Greater Olkaria geothermal system ........................................................................ 6 2.2 The Reykjanes and Svartsengi geothermal fields .......................................................... 7 2.3 Nesjavellir geothermal field........................................................................................... 9 3. SAMPLING AND ANALYSIS............................................................................................. 11 3.1 Sample collection......................................................................................................... 11 3.2 Analysis of water and steam samples .......................................................................... 12 4. FLUID COMPOSITIONS ..................................................................................................... 13 5. CALCULATION OF AQUIFER FLUID COMPOSITION.................................................. 15 5.1 Discharge enthalpy of wells......................................................................................... 15 5.2 Calculation of gas concentrations in steam at atmospheric pressure ........................... 17 5.3 Calculation of aquifer water compositions and speciation distribution....................... 18 6. POTENTIAL CORROSION BY CO 2 AND HCl .................................................................. 20 6.1 Carbon dioxide............................................................................................................. 20 6.2 Hydrogen chloride ....................................................................................................... 22 7. SCALING IN WELLS AND SURFACE INSTALLATIONS .............................................. 28 7.1 Theoretical aspects of calcite scale formation ............................................................. 28 7.2 Scaling tests at Nesjavellir........................................................................................... 30 7.2.1 Test coupons.................................................................................................. 31 7.2.2 Test procedures and selection of test sites for the study................................ 32 7.3 Analysis of scales......................................................................................................... 33 7.3.1 Binocular microscope descriptions................................................................ 34 7.3.2 Fourier transform infrared measurement....................................................... 35 7.3.3 X-ray diffraction measurements .................................................................... 35 7.3.4 Chemical analysis by Scanning Electron Microscopy – Electron Dispersive Spectroscopy (SEM-EDS) ......................................... 37 7.3.5 Chemical analysis of scales by the Inductively Coupled Plasma – Atomic Emission Spectra (ICP-AES)......................................................... 38 7.3.6 Analysis of scales in the UV spectroscopy.................................................... 38 7.3.7 Quantity of scales .......................................................................................... 38 8. EVALUATION OF SCALES DEPOSITED AT OLKARIA WELL OW-34, KENYA....... 41 8.1 Output characteristics of well OW-34 ......................................................................... 41 8.2 Water composition of well OW-34.............................................................................. 42 8.3 Chloride concentration as a function of vapour pressure at selected discharge enthalpies ................................................................................ 42 8.4 Scales deposited at well OW-34 .................................................................................. 43 8.5 Analysis of scales from well OW-34........................................................................... 44 vi
Page 9. CONCLUSIONS ................................................................................................................... 47 REFERENCES ................................................................................................................... 49 APPENDIX A: Tables with analyses, calculation etc..................................................................... 57 APPENDIX B: Methods for preparing coupons and studying scales ............................................. 65 APPENDIX C: Analyses of scales and scales spectra .................................................................... 66 LIST OF FIGURES 1. Kenya Rift system and the major geothermal prospect and Olkaria geothermal field............. 6 2. Location of the geothermal fields in the Greater Olkaria Geothermal Area............................ 7 3. Simplified geological map with high-temperature geothermal fields in Iceland ..................... 8 4. Location of wells in Reykjanes geothermal field..................................................................... 8 5. Well locations in the Svartsengi geothermal field ................................................................... 9 6. Resistivity map delineating the lateral extent of the Hengill geothermal area......................... 9 7. Location of wells in the Nesjavellir geothermal field ............................................................ 10 8. Steam collection using a Webre separator and water sample collection from a weirbox ...... 11 9. Steam collection from a steam separator and water sample collection from a weirbox ........ 11 10. Cl-SO 4 -HCO 3 ternary plot for fluids from the Olkaria, Reykjanes and Svartsengi fields ..... 13 11. Relationship between tqtz vs. tNaK equilibrium temperatures.............................................. 16 12. Difference between tNa/K and tqtz geothermometer temperatures vs. enthalpy................... 16 13. Aquifer temperatures vs. CO 2 partial pressures in the aquifer fluids..................................... 20 14. Aquifer pH vs CO 2 partial pressures in the aquifer for selected wells in the study areas ...... 21 15. CO 2 in the separated water of selected wells with single-step adiabatic steam loss .............. 22 16. CO 2 in the separated water of selected wells with single-step adiabatic steam loss .............. 22 17. Condensate pH at separation temperatures of selected wells in the study area ..................... 22 18. Aquifer water HCl concentrations vs. aquifer water chloride concentrations in wells.......... 24 19. Aquifer water HCl concentrations vs. aquifer water pH of selected wells in the study area . 24 20. Aquifer water HCl concentrations vs. aquifer temperature of selected wells ........................ 25 21. HCl in vapour formed by single-step adiabatic boiling of selected wells in the study areas. 25 22. HCl in vapour with changes in pH upon single-step adiabatic boiling of selected wells ...... 26 23. Aquifer pH vs calcite saturation for Olkaria, Reykjanes, Svartsengi and Nesjavellir ........... 28 24. Changes in calcite produced by single-step adiabatic steam loss for selected well fluid....... 29 25. Calculated aquifer water pH for selected wells and changes in pH during single-step adiabatic steam loss........................................................................ 30 26. Simplified process diagram of the Nesjavellir co-generation power plant. ........................... 31 27. Prepared test coupons with imprinted identification number codes ...................................... 31 28. Retractable coupon holders ................................................................................................... 32 29. Coupons at the well head of well NJ-14 ................................................................................ 33 30. Coupons at entry to the retention tank ................................................................................... 33 31. Coupons at the re-injection well ............................................................................................ 33 32. Test coupons after 13 weeks test period ................................................................................ 34 33. Deposition of scales on test coupons at different locations ................................................... 34 34. IR spectra of scales deposited on coupons at various locations............................................. 36 35. XRD spectra of scales formed at wellheads of Nesjavellir wells .......................................... 37 36. Scanning Electron Micrograph showing crystals of sulphides from scale on test coupons... 37 37. Weight gain of scale at various test sites for 13 weeks test and 29 weeks test ...................... 39 38. Scale thickness at the various test sites for 13 weeks test and 29 weeks test......................... 40 vii
- Page 1 and 2: GEOTHERMAL TRAINING PROGRAMME Repor
- Page 3 and 4: INTRODUCTION The Geothermal Trainin
- Page 5: ABSTRACT The Olkaria geothermal sys
- Page 9 and 10: 1. INTRODUCTION For many countries
- Page 11 and 12: deposition does not occur at depth
- Page 13 and 14: The rate of sulphide precipitation
- Page 15 and 16: the Western Sectors. The Olkaria II
- Page 17 and 18: 46.4 MWe and 125 MWt. A shallow ste
- Page 19 and 20: 3. SAMPLING AND ANALYSIS 3.1 Sample
- Page 21 and 22: 4. FLUID COMPOSITIONS The compositi
- Page 23 and 24: 5. CALCULATION OF AQUIFER FLUID COM
- Page 25 and 26: increases the difference in tNaK -
- Page 27 and 28: The procedure for calculating aquif
- Page 29 and 30: Concentrations of CO 2 at equilibri
- Page 31 and 32: High concentrations of HCl can be g
- Page 33 and 34: variation in chloride concentration
- Page 35 and 36: A 240°C a steam cap overlies the l
- Page 37 and 38: The solubility of CO 2 in water cha
- Page 39 and 40: where it passes through mist elimin
- Page 41 and 42: Coupon holder loosened the screws a
- Page 43 and 44: Coupon # 20 (Re-injection well): A
- Page 45 and 46: 1900 1800 C #10 Well NJ-14 1700 160
- Page 47 and 48: 0,3 13 Weeks (06-07-2005 to 14-10-2
- Page 49 and 50: 8. EVALUATION OF SCALES DEPOSITED A
- Page 51 and 52: atmospheric pressure. The results d
- Page 53 and 54: The IR spectra of scale samples #1
- Page 55 and 56: 9. CONCLUSIONS Olkaria well fluids
TABLE OF CONTENTS<br />
Page<br />
1. INTRODUCTION ................................................................................................................... 1<br />
1.1 Corrosion <strong>in</strong> geothermal environments.......................................................................... 1<br />
1.2 Scale form<strong>at</strong>ion.............................................................................................................. 2<br />
1.2.1 Silica................................................................................................................ 2<br />
1.2.2 Calcite.............................................................................................................. 4<br />
1.2.3 Other scales ..................................................................................................... 4<br />
1.2.4 Objectives of study .......................................................................................... 5<br />
2. GEOLOGICAL FEATURES OF THE STUDY AREA.......................................................... 6<br />
2.1 The Gre<strong>at</strong>er Olkaria geothermal system ........................................................................ 6<br />
2.2 The Reykjanes <strong>and</strong> Svartsengi geothermal fields .......................................................... 7<br />
2.3 Nesjavellir geothermal field........................................................................................... 9<br />
3. SAMPLING AND ANALYSIS............................................................................................. 11<br />
3.1 Sample collection......................................................................................................... 11<br />
3.2 Analysis of w<strong>at</strong>er <strong>and</strong> steam samples .......................................................................... 12<br />
4. FLUID COMPOSITIONS ..................................................................................................... 13<br />
5. CALCULATION OF AQUIFER FLUID COMPOSITION.................................................. 15<br />
5.1 Discharge enthalpy of <strong>wells</strong>......................................................................................... 15<br />
5.2 Calcul<strong>at</strong>ion of gas concentr<strong>at</strong>ions <strong>in</strong> steam <strong>at</strong> <strong>at</strong>mospheric pressure ........................... 17<br />
5.3 Calcul<strong>at</strong>ion of aquifer w<strong>at</strong>er compositions <strong>and</strong> speci<strong>at</strong>ion distribution....................... 18<br />
6. POTENTIAL CORROSION BY CO 2 AND HCl .................................................................. 20<br />
6.1 Carbon dioxide............................................................................................................. 20<br />
6.2 Hydrogen chloride ....................................................................................................... 22<br />
7. SCALING IN WELLS AND SURFACE INSTALLATIONS .............................................. 28<br />
7.1 Theoretical aspects of calcite scale form<strong>at</strong>ion ............................................................. 28<br />
7.2 Scal<strong>in</strong>g tests <strong>at</strong> Nesjavellir........................................................................................... 30<br />
7.2.1 Test coupons.................................................................................................. 31<br />
7.2.2 Test procedures <strong>and</strong> selection of test sites for the study................................ 32<br />
7.3 Analysis of scales......................................................................................................... 33<br />
7.3.1 B<strong>in</strong>ocular microscope descriptions................................................................ 34<br />
7.3.2 Fourier transform <strong>in</strong>frared measurement....................................................... 35<br />
7.3.3 X-ray diffraction measurements .................................................................... 35<br />
7.3.4 Chemical analysis by Scann<strong>in</strong>g Electron Microscopy –<br />
Electron Dispersive Spectroscopy (SEM-EDS) ......................................... 37<br />
7.3.5 Chemical analysis of scales by the Inductively Coupled Plasma –<br />
Atomic Emission Spectra (ICP-AES)......................................................... 38<br />
7.3.6 Analysis of scales <strong>in</strong> the UV spectroscopy.................................................... 38<br />
7.3.7 Quantity of scales .......................................................................................... 38<br />
8. EVALUATION OF SCALES DEPOSITED AT OLKARIA WELL OW-34, KENYA....... 41<br />
8.1 Output characteristics of well OW-34 ......................................................................... 41<br />
8.2 W<strong>at</strong>er composition of well OW-34.............................................................................. 42<br />
8.3 Chloride concentr<strong>at</strong>ion as a function of vapour pressure<br />
<strong>at</strong> selected discharge enthalpies ................................................................................ 42<br />
8.4 Scales deposited <strong>at</strong> well OW-34 .................................................................................. 43<br />
8.5 Analysis of scales from well OW-34........................................................................... 44<br />
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