Limits...
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.


Supercritical reservoirs are related to conventional geothermal resources by fluid mixing.A passive tracer methodology was implemented to trace the flow fluid heated to supercritical conditions through the geothermal system. Colour scale indicates mixing (in terms of mass fraction) of fluid ascending out of the supercritical reservoir (mass fraction 1, red) and cooler liquid and/or vapour (grey tones). Results for the simulations shown in a (Fig. 1d) and b (Fig. 1e). Fluid specific enthalpy contours are shown with red dashed lines.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4525172&req=5

f2: Supercritical reservoirs are related to conventional geothermal resources by fluid mixing.A passive tracer methodology was implemented to trace the flow fluid heated to supercritical conditions through the geothermal system. Colour scale indicates mixing (in terms of mass fraction) of fluid ascending out of the supercritical reservoir (mass fraction 1, red) and cooler liquid and/or vapour (grey tones). Results for the simulations shown in a (Fig. 1d) and b (Fig. 1e). Fluid specific enthalpy contours are shown with red dashed lines.

Mentions: The results bring to light a close relationship between supercritical and conventional high-enthalpy geothermal resources. By tracing the flow of water from the supercritical resource (Methods), we find that conventional high-enthalpy geothermal resources form above supercritical resources as the ascending supercritical water progressively mixes with surrounding cooler water (Fig. 2). In high-permeability host rocks, the focused upflow of supercritical water above the centre of the intrusion mixes with significant amounts of cooler water, reducing water enthalpy to ∼1.5 MJ kg−1 at depths of 1.5–2 km (Fig. 2a). In intermediate permeability systems, a larger amount of ascending supercritical water is mixed with smaller amounts of cooler water, and accordingly the enthalpy of the geothermal system is greater (Fig. 2b). Host rock permeability therefore controls the enthalpy of geothermal systems by affecting both the size of the supercritical water reservoir and the mixing dynamics.


Geologic controls on supercritical geothermal resources above magmatic intrusions.

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

Supercritical reservoirs are related to conventional geothermal resources by fluid mixing.A passive tracer methodology was implemented to trace the flow fluid heated to supercritical conditions through the geothermal system. Colour scale indicates mixing (in terms of mass fraction) of fluid ascending out of the supercritical reservoir (mass fraction 1, red) and cooler liquid and/or vapour (grey tones). Results for the simulations shown in a (Fig. 1d) and b (Fig. 1e). Fluid specific enthalpy contours are shown with red dashed lines.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Supercritical reservoirs are related to conventional geothermal resources by fluid mixing.A passive tracer methodology was implemented to trace the flow fluid heated to supercritical conditions through the geothermal system. Colour scale indicates mixing (in terms of mass fraction) of fluid ascending out of the supercritical reservoir (mass fraction 1, red) and cooler liquid and/or vapour (grey tones). Results for the simulations shown in a (Fig. 1d) and b (Fig. 1e). Fluid specific enthalpy contours are shown with red dashed lines.
Mentions: The results bring to light a close relationship between supercritical and conventional high-enthalpy geothermal resources. By tracing the flow of water from the supercritical resource (Methods), we find that conventional high-enthalpy geothermal resources form above supercritical resources as the ascending supercritical water progressively mixes with surrounding cooler water (Fig. 2). In high-permeability host rocks, the focused upflow of supercritical water above the centre of the intrusion mixes with significant amounts of cooler water, reducing water enthalpy to ∼1.5 MJ kg−1 at depths of 1.5–2 km (Fig. 2a). In intermediate permeability systems, a larger amount of ascending supercritical water is mixed with smaller amounts of cooler water, and accordingly the enthalpy of the geothermal system is greater (Fig. 2b). Host rock permeability therefore controls the enthalpy of geothermal systems by affecting both the size of the supercritical water reservoir and 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.