A.Kamojang Geothermal Field

Imam Raharjo

2010

Typical Andesitic geothermal systemComponents:- heat source- reservoir- cap rock- recharge support

Surface expression :• fumaroles• geysers, hotsprings, etc• hot pool (liquid)• mud pool

• hydrothermal mineral deposits, e.g sinter (SiO2), travertine (CaCO3)• Cold gas seep (CO2), (=kaipohan)•- etc

Vocanoes in Indonesia(www.volcano.si.edu)

Geothermal Prospect in Sumatera (Ministry of Energy and Mineral Resources, 2004)

Sibayak 12MW

SilangkitangNamora-ilangit

Lumutbalai

Ulubelu

Salak 375MW

W- Windu 110MW

Darajat 255MW

Kamojang 200MW

Dieng 60MW

Geothermal Prospect in Java & Bali (Ministry of Energy and Mineral Resources, 2004)

Patuha

Karaha Bodas

Bedugul

Kamojang steam field• Vapor reservoir• T=240° C• P= 35 bar

• Dutch 1926-1928 : five shallow wells

• Pertamina 70’s: drill deep wells

• 1978: 0.25 MW turbine• 1983 : 30 MW• 1988 : 2x 55 MW• 2007 : 60 MW

KMJ Magnetotelluric sites

Resistivity Structure from MTKMJ line B (using 2D FE Wannamaker 2009)

°C

°C

Resistivity Structure from MTKMJ line C (using 2D FE Wannamaker 2009)

°C

°C

Summary : MT KMJ

• The conductor (< 10 ohm.m) is in agreement with smectite zone, having the temperature of up to 150 °C

• The conductor is thin over the reservoir. It thickens and deepens to the side of the reservoir

• The underlying slightly resistive zone (20-80 ohm.m) is also in agreement with the propylitic zone, up to 240 °C

How to create a vapor reservoir (using Tough2)

• Imperm. wall• Discharge lid• Recharge shell• Heat input at • the bottom

Modeling a vapor/liquid geothermal reservoir

8.80 simul. t

in 103 yr

- 600 m -

thickness of steam zone

A

Temperature evolution from model A

b a c d e f g h i

j k l m

KMJ : model vs measured Tj k l m

Pressure evolution from model A

i h g f e d c b am l k j

KMJ : model vs measured P

(abs)

8.8 kyears

8.6 kyears

Summary : Vapor reservoir in a volcanic environment

• impermeable wall (k ~1E-18 m2)• slightly impermeable recharge (k ~1E-17 m2)• moderately impermeable discharge(k ~1E-16 m2)• high heatflow to the bottom of the reservoir, 8

MW/km2, short lived impulses from intrusions• eight thousand years to develop the liquid system,

800 hundred years to convert the liquid into steam

Vapor reservoir issue : • source of the steam : (a) underlying liquid; (b)

immobile water in pores • limited recharge, a careful reinjection is needed• production decline

(Suryadarma, et.al., 2010)

KMJ feedzone pressure decline (Suryadarma, et.al., 2010)

80’s-90’s 2008

4 km

B. Resource assessment (exploration stage)

• prospect size : from geophysical & geological studies

• temperature, from geochemical study or downhole measurement

• predict the system : vapor? liquid ?• volumetric heat stored calculation

(MonteCarlo Simulation)

vertical & lateral extent ?

Volumetric heat stored

anomalous heat

Q = mr cr ∆T (1-φ) + ml ∆hl φ sl + mv ∆hv φ sv

P = (Q R η ) / t

R : recovery factorη : conversion efficiencyt : project duration

normal geotherm

anomalous heat w.r.t normal geotherm

Temperature, deg C 0 100 200

D

epth

, k

m 2

.0

1.5

1.0

0.5

0

Exercise example

C. Economic Assessment

• Installed Capacity• Specific steam consumption• Construction time• Tax• Site preparation• Drillings success ratio• Production well outputs• Reinjection well capacities

• Production decline• Drilling duration &

cost• Project life • Energy price,

escalation• Inflation• Load factor• O&M cost

MonteCarlo simulation for economic assessment

Monte Carlo Sim. Box

cashflow (t)

internal rate of return (IRR)

well prod. cap .

drilling cost

…

Exercise example

Thank you

Thank you

Output example