Deposition of calcium carbonate minerals from geothermal waters — theoretical considerations

Geothermal reservoir waters are generally calcite saturated. Some waters with high temperatures ( >300° C ) may be undersaturated. Boiling causes a drastic decrease in CO 2 partial pressures which leads to supersaturation and calcite precipitation. The supersaturation reaches maximum soon after b...

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Bibliographic Details
Published in:Geothermics 1989, Vol.18 (1), p.33-39
Main Author: Arnorsson, S
Format: Article
Language:English
Subjects:
150303 - Geothermal Exploration & Exploration Technology- Exploratory Drilling & Well Logging
150903 - Geothermal Engineering- Corrosion, Scaling & Materials Development
152003 - Geothermal Data & Theory- Rock-Water-Gas Interactions
ALKALINE EARTH METAL COMPOUNDS
AQUIFERS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBONATES
CHALCOGENIDES
DATA
DEGASSING
DEPOSITION
FLUIDS
Freshwater
GEOTHERMAL ENERGY
GEOTHERMAL FLUIDS
INFORMATION
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PARTIAL PRESSURE
PERMEABILITY
RESERVOIR ROCK
ROCK-FLUID INTERACTIONS
SALINITY
SOLUBILITY
TEMPERATURE EFFECTS
THEORETICAL DATA
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Summary:Geothermal reservoir waters are generally calcite saturated. Some waters with high temperatures ( >300° C ) may be undersaturated. Boiling causes a drastic decrease in CO 2 partial pressures which leads to supersaturation and calcite precipitation. The supersaturation reaches maximum soon after boiling is initiated. At this maximum the water has been almost quantitatively degassed. Further boiling, which leads to cooling, will cause successively decreasing supersaturation as the solubility of calcite increases with decreasing temperature. The magnitude of supersaturation is largely controlled by the initial temperature and the salinity of the geothermal water, being highest when salinity is highest and temperature lowest. Calcite deposition tends to be troublesome only when the first level of boiling is in the well. When extensive boiling starts in the aquifer, calcite precipitation is not experienced although it is expected to occur in the formation. The pore volume in the reservoir is much larger than that of individual wellbores and can cope with calcite deposition without observable deterioration of permeability for periods as long as the lifetime (20–50 years) of individual wells.
ISSN:0375-6505
1879-3576
DOI:10.1016/0375-6505(89)90007-2