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Geologic controls on supercritical geothermal resources above magmatic intrusions.

Scott S, Driesner T, Weis P - Nat Commun (2015)

Bottom Line: Conventional high-enthalpy resources result from mixing of ascending supercritical and cooler surrounding water.Our models reproduce the measured thermal conditions of the resource discovered at Krafla.Similar resources may be widespread below conventional high-enthalpy geothermal systems.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth Sciences, Institute of Geochemistry and Petrology, ETH Zurich, Clausiusstrasse 25, 8092 Zurich, Switzerland.

ABSTRACT
A new and economically attractive type of geothermal resource was recently discovered in the Krafla volcanic system, Iceland, consisting of supercritical water at 450 °C immediately above a 2-km deep magma body. Although utilizing such supercritical resources could multiply power production from geothermal wells, the abundance, location and size of similar resources are undefined. Here we present the first numerical simulations of supercritical geothermal resource formation, showing that they are an integral part of magma-driven geothermal systems. Potentially exploitable resources form in rocks with a brittle-ductile transition temperature higher than 450 °C, such as basalt. Water temperatures and enthalpies can exceed 400 °C and 3 MJ kg(-1), depending on host rock permeability. Conventional high-enthalpy resources result from mixing of ascending supercritical and cooler surrounding water. Our models reproduce the measured thermal conditions of the resource discovered at Krafla. Similar resources may be widespread below conventional high-enthalpy geothermal systems.

No MeSH data available.


The thermal structure of high-enthalpy geothermal systems.Pressure–enthalpy ascent paths were extracted from selected simulations shown in Fig. 1 and Supplementary Fig. 2, and are superimposed onto a phase diagram of water showing the region of two-phase liquid and vapour coexistence and isotherms. The areas of potentially exploitable supercritical fluid, single-phase vapour and two-phase fluid are shown in red, green, and blue, respectively. The measured reservoir temperature and enthalpy for the IDDP-1 well (450 °C, 3.2 MJ kg−1)11 is shown with a yellow star.
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f3: The thermal structure of high-enthalpy geothermal systems.Pressure–enthalpy ascent paths were extracted from selected simulations shown in Fig. 1 and Supplementary Fig. 2, and are superimposed onto a phase diagram of water showing the region of two-phase liquid and vapour coexistence and isotherms. The areas of potentially exploitable supercritical fluid, single-phase vapour and two-phase fluid are shown in red, green, and blue, respectively. The measured reservoir temperature and enthalpy for the IDDP-1 well (450 °C, 3.2 MJ kg−1)11 is shown with a yellow star.

Mentions: The combined effects of TBDT, host rock permeability and intrusion depth on supercritical resources and on the thermal structure of geothermal systems can be summarized in a pressure–enthalpy (p–h) diagram (Fig. 3). In systems with a low TBDT and high host rock permeability (blue solid line), enthalpy is reduced to ≤1.5 MJ kg−1 after mixing, giving rise to a geothermal system with boiling restricted to shallow depths. In systems with a high TBDT (red lines) and/or intermediate permeability (dotted lines), the higher enthalpy input and lower degree of mixing leads to geothermal systems that boil over the entire depth range above the supercritical resource. The transition from supercritical to boiling conditions occurs over a small pressure range in high-permeability systems and more gradually in intermediate permeability systems, reflecting the mixing dynamics.


Geologic controls on supercritical geothermal resources above magmatic intrusions.

Scott S, Driesner T, Weis P - Nat Commun (2015)

The thermal structure of high-enthalpy geothermal systems.Pressure–enthalpy ascent paths were extracted from selected simulations shown in Fig. 1 and Supplementary Fig. 2, and are superimposed onto a phase diagram of water showing the region of two-phase liquid and vapour coexistence and isotherms. The areas of potentially exploitable supercritical fluid, single-phase vapour and two-phase fluid are shown in red, green, and blue, respectively. The measured reservoir temperature and enthalpy for the IDDP-1 well (450 °C, 3.2 MJ kg−1)11 is shown with a yellow star.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525172&req=5

f3: The thermal structure of high-enthalpy geothermal systems.Pressure–enthalpy ascent paths were extracted from selected simulations shown in Fig. 1 and Supplementary Fig. 2, and are superimposed onto a phase diagram of water showing the region of two-phase liquid and vapour coexistence and isotherms. The areas of potentially exploitable supercritical fluid, single-phase vapour and two-phase fluid are shown in red, green, and blue, respectively. The measured reservoir temperature and enthalpy for the IDDP-1 well (450 °C, 3.2 MJ kg−1)11 is shown with a yellow star.
Mentions: The combined effects of TBDT, host rock permeability and intrusion depth on supercritical resources and on the thermal structure of geothermal systems can be summarized in a pressure–enthalpy (p–h) diagram (Fig. 3). In systems with a low TBDT and high host rock permeability (blue solid line), enthalpy is reduced to ≤1.5 MJ kg−1 after mixing, giving rise to a geothermal system with boiling restricted to shallow depths. In systems with a high TBDT (red lines) and/or intermediate permeability (dotted lines), the higher enthalpy input and lower degree of mixing leads to geothermal systems that boil over the entire depth range above the supercritical resource. The transition from supercritical to boiling conditions occurs over a small pressure range in high-permeability systems and more gradually in intermediate permeability systems, reflecting the mixing dynamics.

Bottom Line: Conventional high-enthalpy resources result from mixing of ascending supercritical and cooler surrounding water.Our models reproduce the measured thermal conditions of the resource discovered at Krafla.Similar resources may be widespread below conventional high-enthalpy geothermal systems.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth Sciences, Institute of Geochemistry and Petrology, ETH Zurich, Clausiusstrasse 25, 8092 Zurich, Switzerland.

ABSTRACT
A new and economically attractive type of geothermal resource was recently discovered in the Krafla volcanic system, Iceland, consisting of supercritical water at 450 °C immediately above a 2-km deep magma body. Although utilizing such supercritical resources could multiply power production from geothermal wells, the abundance, location and size of similar resources are undefined. Here we present the first numerical simulations of supercritical geothermal resource formation, showing that they are an integral part of magma-driven geothermal systems. Potentially exploitable resources form in rocks with a brittle-ductile transition temperature higher than 450 °C, such as basalt. Water temperatures and enthalpies can exceed 400 °C and 3 MJ kg(-1), depending on host rock permeability. Conventional high-enthalpy resources result from mixing of ascending supercritical and cooler surrounding water. Our models reproduce the measured thermal conditions of the resource discovered at Krafla. Similar resources may be widespread below conventional high-enthalpy geothermal systems.

No MeSH data available.