corrosive species and scaling in wells at olkaria ... - Orkustofnun

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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
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