Page 127 - Geothermal Energy Systems Exploration, Development, and Utilization

References 103
the liquid. It is evident that the operating pressures of wellhead steam separators
must be decided considering the pH of the liquid phase to avoid silica scaling. If
the salinity of the geothermal liquid is higher than that of seawater, its effect on
amorphous silica solubility has to be considered too (Fournier, 1991). Deposition
of amorphous silica from supersaturated water could possibly be reduced, even
◦
inhibited, by rapid cooling of the water to 50 C or less (Gunnarsson and Arnorsson,
2007).
Calcium carbonate scaling often occurs because almost all geothermal systems
contain dissolved carbon dioxide. Prevention of calcium carbonate scaling can be
achieved by alteration of either the partial pressure of carbon dioxide or the pH,
and also by adding chemical scale inhibitors (Stamatakis et al., 2006). Good results
were obtained with the sodium polyacrylate (Yanagisawa, Matsunaga, and Sugita,
2006). Acidification is also known to lower the rate of deposition and to prevent
silica scaling. Mixing of condensate and brine should always be considered as a
possible means of preventing scaling in injection wells.
Safe disposal of thermally spent geothermal brines that contain environmentally
hazardous constituents is commonly obtained by reinjection. During the exploita-
tion phase, the reinjection process also serves to maintain reservoir pressure,
enhance thermal recovery, and eliminate possible compactional subsidence.

References
¸
Akkus, I., Akilli, H., Ceyhan, S., Dilemre, Arnorsson, S. and Gunnlaugsson, E. (1985)
A., and Tekin, Z. (2005) T¨ urkiye Jeotermal New gas geothermometers for geothermal
Kaynaklari Envanteri: Envanter Serisi, exploration – calibration and applica-
Ankara, 849 p. tion. Geochimica Cosmochimica Acta,
Anderson, E.M. (1951) The Dynamics of 49, 1307–1325.
Faulting, Oliver & Boyd, London, 83 p. Arnorsson, S., Gunnlaugsson, E., and
Aquilina, L. and Brach, M. (1995) WELCOM Svavarsson, S. (1983) The chemistry
(Well Chemical On-line Monitoring): evo- of geothermal waters in Iceland. III.
lution of chemical monitoring of drilling Chemical geothermometry in geothermal
fluids and industrial perspectives. Soci- investigations. Geochimica Cosmochimica
ety of Petroleum Engineers, Drilling and Acta, 47, 567–577.
Completion, 158–164. Avseth,P.,Mukerji, T.,and Mavko,G.
´ Arnason, K., Eysteinsson, H., and Hersir, (2005) Quantitative Seismic Interpretation,
G. (2010) Joint 1-D inversion of TEM and Cambridge University Press, 356 p.
MT data and 3D inversion of MT data Barton, C.A., Zoback, M.D., and Moos, D.
in the Hengill area, SW Iceland. Special (1995) Fluid flow along potentially active
volume about the European I-GET project. faults in crystalline rock. Geology, 23 (8),
Geothermics, 39 (1), in press. 683–686.
Archie, G.E., (1942) The electrical resistivity Bertrami, R., Cioni, R., Corazza, E.,
log as an aid in determining some reser- D’Amore, F., and Marini, L. (1985) Carbon
voir characteristics. Petroleum Transactions monoxide in geothermal gases. Reservoir
American Institute of Mining, Metallurgical, temperature calculations at Larderello
and Petroleum Engineers 146, 54–62. (Italy). Geothermal Research Council Trans-
Arnorsson, S. (ed.) (2000) Isotopic and Chem- actions, 9, 299–303.
ical Techniques in Geothermal Exploration, Bowen, R. (1989) Geothermal Resources,2nd
Development and Use, International Atomic edn, Elsevier Applied Science, London,
Energy Agency, Vienna, p. 351. p. 485.