Post on 17-Jan-2017
Updated conceptual model of Hellisheiði geothermal field
Anette K. Mortensen, Bjarni Reyr Kristjánsson,
Gunnar Gunnarsson, Ingvi Gunnarsson,
Einar Gunnlaugsson, Edda Sif Aradóttir,
Gretar Ívarsson
GGW 2016
25. november 2016
2
• Defines the natural proporties of the geothermal system
– in particular interaction between temperature, pressure,
permeability and mass/energy flow in the system
Conceptual Models of Geothermal Systems
Fractured zonePrecipitation
Recharge
InflowTemperature
Upflow
Outflow
Pressure
Permeability
Lithology
Fluid composition
Size (area, thickness)
Production
ReinjectionFractures and faults
Heat source
Conceptual Model of Hellisheiði
» Latest review in 2007» 10 years production history and much more knowledge gained
»Objective:• More clear concept of salient properties of
the geothermal reservoir and the effect of production
• Basis for management of production and reinjection in the coming years
• Foundation for future location of production wells and reinjection wells
• Updated research plan
Local Heat Sources
Heat sources and their attributes:
1. At eruptive fissure south of Skarðsmýrarfjall » High permeability and
vigorous convection
2. Mini-graben at Reykjafelli » High temperature,
lower permeability, weak convection
3. Hverahlíð – Intersecting faults» High temperature,
high permeability
Skarðsmýrarfjall
Reykjafell
Hverahlíð
HengillFormation temperature at 1000 m.u.s.l.
Initial State – Geochemical Composition
Cl/B´moleratio
Hot
ste
am p
roce
ssR
ock
ratio
Pos
s. e
ffect
of
seaw
ater
?
At least three compartments based on Cl/B ratio 10 100
Styrkur klór í jarðhitavatni (mg/kg)
1
10
100
1000
10000
Cl/B
í ja
rðhi
tava
tni
Cl/B sjór og úrkoma
Cl/B berg
Heitt gufuferli sem leiðir til of mikils bór í vatninu miðað við klór
Úrkoma Hellisheiði
Cl concentration in geothermal water (mg/kg)
Cl/B
in in
geo
ther
mal
wat
er
Precipitation at Hellisheiði
Cl/B of seawater and rain
Hot steam process, which results in high concentration of B in the water in comparison to Cl
rock
Fault Controlled Permeability
• Permeability connected to
NE-SW striking
rift faults and fissures
• Low permeability perpendicular to the orientation of main faults
Tracer Tests
Reservoir Response to Production
Decline in well outputPressure drawdownAccumulated production
kg/s pr. yr
Cooling in the Reservoir
• Up to 20°C cooling in wells at eruptive fissure• Cooling most in aquifers at 800-1400 m depth – cooling from boiling due to pressure drawdown • Cooling minimal in wells with pressure support from reinjection
Delta temp. Qz geotherm. (°C)
Cooling acc. to Qz geothermometer (°C)
Dep
th o
f aqu
ifers
(m.b
.s)
Production at Hellisheiði
Compartments Controlled by Faults and Fissures
900 kg/s
1200 kg/s
Reinjection
Production
Húsmúli
Gráhnúka
Hverahlíð
Skarðsmýrarfjall
Size of Production FieldProduction at Hellisheiði is distributed over a 14 km2 large area
» Skarðsmýrarfjall: Area: 5
km2
Output: 51 MWe Output/km2: 10 MWe/km2
» Hellisheiði and Reykjafell: Area: 9 km2
Output: 193 MWe Output/km2: 21 MWe/km2
» Hverahlíð: Area: 5 km2
Output: 53 MWe Output/km2: 11 MWe/km2
Measures:
More distributed reinjection
Enlarge production area
Current reinjection areas
Planned reinjection areas
Maintain Production