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| Titel |
Geochemical modelling of EGS fracture stimulation applying weak and strong acid treatments |
| VerfasserIn |
Bergur Sigfusson, Edda Sif Pind Aradottir |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250112771
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| Publikation (Nr.) |
 EGU/EGU2015-12947.pdf |
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| Zusammenfassung |
| Engineered Geothermal systems (EGS) provide geothermal power by tapping into the
Earth’s deep geothermal resources that are otherwise not exploitable due to lack of
water and fractures, location or rock type. EGS technologies have the potential
to cost effectively produce large amounts of electricity almost anywhere in the
world.
The EGS technology creates permeability in the rock by hydro-fracturing the reservoir
with cold water pumped into the first well (the injection well) at a high pressure. The
second well (the production well) intersects the stimulated fracture system and
returns the hot water to the surface where electricity can be generated. A significant
technological hurdle is ensuring effective connection between the wells and the fracture
system and to control the deep-rooted fractures (can exceed 5Â000Âm depth). A
large area for heat transfer and sufficient mass flow needs to be ensured between
wells without creating fast flowing paths in the fracture network. Maintaining flow
through the fracture system can cause considerable energy penalty to the overall
process. Therefore, chemical methods to maintain fractures and prevent scaling can be
necessary to prevent excessive pressure build up in the re-injection wells of EGS
systems.
The effect of different acid treatments on the porosity development of selected rock types
was simulated with the aid of the Petrasim interface to the Toughreact simulation code. The
thermodynamic and kinetic database of Aradottir et al. (2014) was expanded to include new
minerals and the most important fluoride bearing species involved in mineral reactions during
acid stimulation of geothermal systems. A series of simulations with injection waters
containing fluoric acid, hydrochloric acid and CO2 or mixtures thereof were then carried out
and porosity development in the fracture system monitored. The periodic injection of weak
acid mixtures into EGS systems may be cost effective in some isolated cases to
prevent pressure build-up and therefore lowering pumping costs during operation.
Selection of the acid is though highly dependent on the chemistry of the reservoir in
question.
Reference
Aradottir, E. S. P., Gunnarsson, I., Sigfusson, B., Gunnarsson, G., Juliusson, B. M.,
Gunnlaugsson, E., Sigurdardóttir, H., Arnarson, M. T., Sonnenthal, E., 2014. Toward Cleaner
Geothermal Energy Utilization: Capturing and Sequestering CO2 and H2S Emissions from
Geothermal Power Plants. Transport in Porous Media. DOI 10.1007s/11242-014-0316-5 |
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