Bedugul Geothermal Prospect and Developments

Proceedings World Geothermal Congress 2005 Antalya, Turkey, 24-29 April 2005

Achmad Mulyadi, Edwin J. Joenoes and Ni Made Widiasari By Pass Ngurah Rai No. 88, Sanur, Denpasar, Bali [email protected]; [email protected]

Keywords: Bali, Bedugul, hot water system, (10 + 3 x 55) The Balinese have a one management island concept called MWe, high silica contents, stimulated discharging well, seamount union. Whenever one changes the mount friendly environment, cultural ceremonial. environment, the sea environment will change. Bedugul is a part of the attractive tourist area in Bali. Therefore when ABSTRACT developing a geothermal area in Bedugul, it is necessary to follow the wishes of the Balinese. For example: by keeping Bedugul is in the center of Bali and north of Denpasar. A Bali clean, the environment is sustained and at the end of geothermal area exists there. The area is about 70-90 km2 the project tourism will have increased. and is bordered mainly from geophysics and geology investigations. Part of the area was proven by the BEL previously anticipated the need for developing exploration of two deep wells BEL-03 and BEL-02, and geothermal energy in Bali by conducting an energy core-hole TCH-04. It is inside Bratan’s caldera structure. workshop in 1977. Recently, BEL has begun introducing Therefore, the proven area of geothermal prospect is then geothermal energy to the Balinese. defined to be about 8 km2. The area may conserve energy of about 80 MWe for 30 years since its power density is equal to 10MW each km2. Bali Energy Limited (BEL) will 1. INTRODUCTION promote a small power of 10 MWe in 2006 to initiate The concession area of Bedugul geothermal was referred to th another large 3 x 55 MWe power for the future. letter 465/KPTS/M/Pertamb./74 on April 10 , 19974. It is delineated by coordinates of 8o10’00” – 8o30’30”S and Geothermal energy is a prospective alternative energy that 8o11’30” – 8o26’30”E, 101 660 Ha, see figure 1. would be used for generating electricity for Balinese desire. Its products should only have a small affect on the environment, and they may increase the existing tourism.

Figure 1: The concession area (WKP) of Bedugul.

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In November 17, 1995, the joint operation contract (JOC) Holocene period. The system is in N-S trending volcanic was signed by PERTAMINA and Bali Energy Limited. activities in the big Bratan caldera. Meanwhile, on the same day the energy sales contract (ESC) was also signed by Bali Energy Limited and pt. PLN Volcanic rocks are distributed on most of the prospect area, (persero). Unfortunately, most of the big projects including and sedimentary rocks are near the lakes within the Bratan Bali geothermal project were suspended when the economic caldera. The surface layer consisted mainly of tuff, tuff crises took over Indonesia in 1997. During its exploration lapilli, and alluvium; the layer is very loose and tends to period before being suspended by the president’s decree erode easily. Flowed pumice ash tuff covers most of the number 39 in the year 1997, BEL had managed to drill six center and eastern part of Bali, which overlies andesitic temperature core holes and three deep exploration wells. volcanic. They were named BEL-01, BEL-02, and BEL-03. In the last stages of the exploration period at the end of January Surface thermal features within Bratan Caldera include 1998, BEL performed a 24 hours rig test on well BEL-03. drowned fumaroles (Teratai Bang) and an area of warm The test yielded the result that BEL-03 was able to produce ground at an elevation of 1400-1500 meters above mean sea steam and water of up to 56t/h with an enthalpy of 1744 level (amsl). Also it includes as a warm spring on the edge kJ/kg. After that, the Bedugul Geothermal Project went of Lake Buyan. In addition, a hot spring area is present at a into suspension. lower elevation on the west flank of the volcanic highlands at Yeh Panas at about 600 meters amsl. A cold spring is Five years later, in 2002, continuations of big projects were present on the eastern flank, as well as an extensive area of re-negotiated with the issuance of the President’s decree Hot Springs on the southern flank at elevations of 300-600 number 15. After 18 months of re-negotiation that meters amsl. produced amendments to the original JOC and ESC contracts, the Bedugul Geothermal Project was once again In 2004, Jetro-WestJec has recently reconstructed ready to go forward with full government support. This lithological cutting obtained from wells that show was partly because there was a concern of a Java-Bali dominated pyroclastic, andesite, and underlain by andesite electricity shortage in the near future. Therefore, breccias (could be diorite). They also interpreted that the suspensions of Independent Power Producers (IPP) Projects existence of ignimbrite may indicate the Bratan caldera has were revoked including BEL. erupted three times, 29300, 20150, and 5500 BC. Lateral distribution of resistivity sub-stratum showed no 2. LOCATION contrast resistivity boundary found, unless the two areas are The Bedugul geothermal prospect is located in the at the northwest and the south part of the area, figure 2. A mountain area and it is about 60 km north of Denpasar, diffuse sub-surface resistivity boundary seems to exist Bali, figure 1. Two volcanoes, Mt Batur and Mt Agung are towards east and west. The diffuse resistivity boundary is presently active outside of the prospect in the eastern part of also indicated by a more extensive area of relatively; low Bali. Nature preserves or protected forest, production resistivity extends away from the three anomalies of TDEM forest, and botanic gardens cover most of the prospect area, resistivity in the caldera area to the hot spring areas on the and the rest is property of the community. Small fumaroles west and south flanks. This strongly suggests that the hot and very rare warm springs manifested at the center, while springs on the flanks are fed by topographically driven most of warm and cold springs are outside of the area. lateral out-flows of mineral water originating in the caldera area. However, the results of slime holes drilled at the 3. PROSPECT AND PROVEN AREAS southeast of the area may separate the geothermal prospect Since signing the contracts with the government in area from others. While to the west and the east, the November of 1995, BEL has completed geological, gravity boundary of geothermal area is due to the caldera rim and and resistivity surveys, and drilled six temperature gradient the geological structure interpreted from geology photo. core-holes to the depths of 685-1400m, and three deep exploration wells to the depth of 2686-2826 m. Core-hole The Bouguer gravity anomaly indicated by the NE-SW data shows that cold, porous volcanic rocks forms a 1000m trending line may suggest a fault system in the northern and thick blanket over most of the prospect area, effectively the southern part of the area, Jetro-WestJec in 2004, see masking the deep geothermal system and limiting surface figure 2. The fault seems also due to rim caldera at the NE expressions of heat. Temperature measurements in core- edge of the Bratan caldera. The NW-SE lineament is due to holes combined with resistivity survey results indicate the caldera rim at the western edge of Bratan caldera. Bali resource may be quite deep. Production wells may The geothermal prospect area is then inside the moderate have to be drilled to depths of 3,000 – 3,500 meters. resistive sub-stratum and defined by the geological 2 The Bedugul geothermal system, Bali, is associated with structure; it is ending with figure of about 30 km , figure 2. Quaternary volcanic activities in the Pleistocene to

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BEDUGUL-BALI GEOTHERMAL PROPSECT MAP

D. Buyan Legend :

Prospect area

Out-flow area TCH-0 4

G. TAPAK Loc. D D. Bratan Non-prospect area

G. LESUNG Loc. U

- 0 B Loc.G

G. PUCUK 2 E

L TCH-03 TCH-02

Loc.- C 0 Big-hole 3 Loc.Q G. POHEN Slime-hole B E L TCH-06 TCH-01 -0 TCH-05 1 Fumarole Loc.H

G. SENGAYANG Warm Spring

G. ADENG Cold Spring

G. BATUKARO

Figure 2: MT-resistivity sub-stratum map

Figure 3: Top of TDEM conductive layer (Geosystem, 1996

A resistivity model was constructed from 1-D resistivity resistive sub-stratum. The middle conductive layer is layer that inverted from MT-sounding. Layers of the model interpreted as a cap rock. were then simplified into three resistivity layers that consist of surface resistive layer, middle conductive layer, and Top of Time Domain Electro Magnetic (TDEM) conductor may also represent the top of cap rock. By mapping, the

3 Mulyadi et. al top of conductor may indicate cap rock distribution and its resistivity model in figure 5, shows that the top of resistive shape. The conductor formed dome like structure in center basement is deeper than the inferred hot chloride water of the area around Mt. Tapak and it is also shown in the level. The hot chloride water was inferred from well test south-west of the area, see figure 3. The pattern is also and down hole pressure-temperature results. Since then, it is similar to the pattern of sub-surface temperature suggesting that the resistivity model should be corrected distributions of deep wells and of core holes. from the existence of ocean water at 30 km north of the prospect area. Key temperature mineral such as epidote mineral, was found at the deep wells named BEL-01, BEL-02 and BEL- BEL-03: T-P Vs Elevation (m) Profile 03. No epidote was found at all slime-holes, even at the 16 March 98 high thermal gradient of core-hole TCH-04. 2000 1800

Sub-surface temperature profiles that were obtained from 1600 the three deep exploration wells BEL-02, BEL-03, BEL-01, 1400 and one core-hole of TCH-04 have high temperature 1200 gradient, suggesting those wells were in an area of up-flow 1000 zone, figure 2 and 4A. Other area defined as out-flow zone 800 was indicated by TCH-01, TCH-02, and -05; while the 600 TCH-06 shows a moderate temperature gradient, suggesting 400 the TCH-06 was located on the boundary between up-flow 200 and out-flow zones, figure 2 and 4B. 0

-200

The conductive layers that exist in the area of the Bedugul (m) Elevation geothermal system are very thick. The bottom of the cap -400 rocks can reach to depth of about 1000-2000m below sea -600 level, figure 5. This depth is unusual in comparison to -800 other geothermal systems in Indonesia. In other systsems -1000 T 31/01/'98 (static 2 hrs) the bottom of cap rocks are usually located from sea level -1200 T 1/02/'98 (static 19 hrs) T 12/02/'98 (static 5 days) to 500m below sea level. -1400 P 12/02/'98 (after pumping air up to 1500 psi) -1600 P (5/4-'04) A common geothermal resistivity layer with an addition of T (5/4-'04) -1800 T(flowing) the presence of ocean water at 30 km north of the prospect P(flowing) -2000 area was modeled. The resistivity value of the ocean water 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 was 0.25 Ωm, which was overlying the 100Ωm resistive T(C) --- P (ksc) body, figure 6. The model was then showing long period response. If this is the case, the long period response of MT, which affected into the calculated tick conductive Figure 4A: P-T profile BEL-03, Bedugul, Bali. layer is due to deep ocean water. Therefore the MT

BEL-TCH Temp. Profile 1500

TCH-01 Kuster survey, 05 Sep 97 P-T PROFILE of BEL-02, BALI

TCH-02 Kuster survey, 06 Sep 97 1300 1700 TCH-03 Kuster survey, 06 Aug 97 1600 1500 TCH-04 Kuster Survey, 15 Sept 97 1400 1100 TCH-05 Kuster Survey, 16 Sept 97 1300 1200 03 1100 1000 900 900 800 700 600 700 500 400 300 200 500 100 0

Elevation (masl) -100 -200 04 VERTICAL DEPTH (m) 300 -300 y = -3.5161x + 677.6 -400 -500 T-grad. = 28°C/100m -600 100 -700 05 -800 -900 -1000

-100 -1100 01 -1200 y = -13.093x + 1011.7 -1300 T-grad. = 7-8°C/100m -1400 0 50 100 150 200 250 300 350 400 -300 02 T(°C) --- P(ksc)

T (°C) - Feb. 16, '98 T (BEL-02, Feb. 7th, '04) T (BEL-02, may 7th '04) Bel-01, Nov. 5, '97 -500 0 50 100 150 200 250 Temperature (deg.C)

Figure 4B: P-T Profiles of slime-holes and well BEL-02.

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Bali MT-Resistivity Section D-D' (Middle Part)

MT-73BEL-02(P) W Mt. Lesong BEL-03(P) MT-69 TCH-04(P) MT-109S E 2000m MT-72 MT-81 MT-048N TCH-02(P) MT-68 MT-75 MT-79 MT-65 100 110 60 L. Bratan 65 1000m 75-100 60 100 50-350 90 1.5 (150) 50 90 3 3.5 0m 8 4 (18) 243°C 8 6483°C -1000m 306°C 325°C

25 30 20 6 -2000m 20 (65) 75 45 -3000m 25 40

-4000m

45 -5000m

-6000m

1000m 5000m 10.000m 15.000m Rho-inv

0verbourden (35-500 ohm-m) Cap Rocks ( 3-8 ohm-m) Out-flow zone

Reservoir Rocks (20-75 ohm-m) Non Geothermal Zone (>100 ohm-m) IInferred top of water level

Figure 5: Tentative resistivity model of Bedugul-Bali.

1 TM 2 TM 3 TM

100 Rho (Ohm-m) TE TE TE 10

PERIOD, second PERIOD, second PERIOD, second

.001 .01 .1 1 10 100 .001 .01 .1 1 10 100 .001 .01 .1 1 10 100

12 3 0 10 0.25 Ohm-m -2 km 5 Ohm-m Ocean

-4 km

-6 KM 100 Ohm-m

-8 km 35 Ohm-m

-10 km

500 Ohm-m

-25 km 0 25 km 50 km 75km 100km 125km 150km 175km LONG PERIOD RESPONCE DUE TO DEEP OCEAN

Figure 6: Long MT-period response due to ocean water

The high sub-surface temperature may coincide with the records there were only two wells, BEL-02 and BEL-03 appearance of mineral epidote that was encountered in all that may indicate permeability. No permeability was in the the deep wells at depth ranging from sea level down to well BEL-01. 1000m below sea level. However, according to drilling 5 Mulyadi et. al

To prove the presence of geothermal potential in the seems very low, since the well is big hole. However, after Bedugul-Bali geothermal prospect, BEL was then planning vertically discharging since end of June 2004, it is to test the well BEL-03. expecting to have BEL-03 producing higher steam. Well BEL-02 will be potentially tested soon after BEL-03 is There is high reservoir temperature, but the top level of the tested, and it is expected to be able to produce steam higher water column reached about 500m to the surface. It than 38 ton/hour. BEL-02 was drilled to the eastern flank suggests that the BEL-03 should be stimulated to discharge. of Mt. Tapak, which has similarity of drilling target with A method by lowering water level down to 1500m deep BEL-03.The steam fraction is dominant up to 95% dryness. using nitrogen compressor was chosen to bleed the well and Since then the steam flashing was interpreted as occurring then the production well test was conducted for an at the depth of 850m below sea level, which was showed by additional month. elevated gradient of pressure at flowing condition, figure 4A. After no response, the well flowing with about 5000 gallon of nitrogen had been pumped into the well BEL-03. It took Total gas content is rather high of about 4%-Wt comparing 2 x 24 hours to well head pressure up to 1450 psi, which is to the rig test of well BEL-03 conducted in 1998 that was similar to pressurize the well where the water level is at 3%weight. There is a trace of magmatic gases such as HF, about sea level, figure 7. HCl, and SO2, table 1. However, its pH is normal. The H2S concentration was 0.0236-0.0302%-weight in steam, which is very common in ordinary geothermal system. Recent gas analyses indicated that the H2S content is extremely high, 2.3%-weight. Other high gas CO2 concentration of 97%-weight was interpreted as derived from sedimentary rocks (limestone). These rocks were outcropped at the south beach of Bali acting as basement.

Since the BEL-03 has been being proven to discharge the steam, part of the prospect area was then defined as proven area. The BEL-02 has similarity in P-T profiles to well BEL-03 and slime-hole TCH-04 indicated high temperature gradient; the caldera structure may provide rock’s permeability. So the wells BEL-03 and BEL-02 and the core-hole TCH-04 are acting as the boundary of the proven area. Therefore, the proven area of geothermal prospect is then defined to be about 8 km2, see figure 9. The proven area is chosen to be used to develop an initial 10 MW Figure 7: Pumping Nitrogen into the well BEL-03. power before developing the other 3 x 55 MW power. Well BEL-03 has been flowed in early May 2004 for 6 weeks showing steam rates from 38 and 36 t/h at a well head pressure of 100 and 200 psi, figure 8A and 8B. It

PRODUCTION TEST BEL-03

P-Lips Water S (t/H) 50

Diameter-pipe = 6" 40 WHP=100psi (st eam = 40t / h) WHP>300psi (steam = 32t /h) WHP=150psi (steam = 39t/h)

30 WHP=200psi (steam = 35t /h)

10 Lip pressure, kscg

0 10 15 20 25 30 35 40 45 50 55 DAY

Figure 8A: Flow rate of BEL-03 Vs Time, Bedugul-Bali.

6 Mulyadi et. al

Well production (BEL-03) test 45

40 100, 39.53 150, 38.52

35 201.52, 35.12

25 419.73, 24.69

Q, t/h 20

10 419.73, 7.32

5 201.52, 4.34 100, 3.02 150, 3.10

0 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450

Qsteam (t/h) Qwater (t/h) Dryness (%) Qmass (t/h) WHP, psi

Figure 8B: Production test of BEL-03, Bedugul-Bali.

Legend : D. Buyan Non-prospect area Production Well

Injection Well Prospect area A New W ell

TCH-0 4

G. TAPAK Proven Area D. Bratan

Nature Preserve G. LESUNG

L Botanic Garden

- B 0 G. PUCUK E 2 L TCH-03 TCH-02 - 0 3 Fumarole G. POHEN Warm Spring BE TCH-06 TCH-01 L- TCH-05 01 Loc.H Cold Spring Out-flow area G. SENGAYANG Geol. structure Out-flow area G. ADENG Geof. Dis- continuity

New Pad G. BATUKARO Non-prospect area

Figure 9: Proven geothermal area, Bali.

7 Mulyadi et. al

Table 1: Gas content of BEL-03 sample analyzed by PT Geoservices, Bandung, 2004.

Parameter %mole %weight Date

CO2 95.76 96.85 4-May-04

H2S 3 2.35 4-May-04 Residual gas 1.24 0.8 4-May-04

CO2 95.67 96.99 17-May-04

H2S 2.93 2.3 17-May-04

SO2 0.0005 0.0008 17-May-04 HCl 0.0045 0.0038 17-May-04 HF 0.0407 0.0188 17-May-04

H2 0.33 0.02 17-May-04 O2 0.332 0.282 17-May-04 N2 0.411 0.265 17-May-04 CO < .0001 < .0001 17-May-04 CH4 0.0081 0.003 17-May-04 C2H6 0.0084 0.0058 17-May-04

Tot. Gas 1.74 4.12 14-May-04 H2O 98.26 95.88 14-May-04 Tot. gas 1.81 4.26 17-May-04 H2O 98.19 95.74 17-May-04

Table 2. WBS-SPW chemical analyses of well BEL-03.

Weir-box Sample (WBS) Separated Water (SPW) PARAMETER May 14th, 2004 May 17th, 2004 May 14th, 2004 May 17th, 2004 pH at 25oC 7.44 7.34 7.41 7.25 o Electr. Cond., 25 C, (µS/cm) 14830 13730 12110 11250 Boron (B), ppm 644 700 475 573 Silica (SiO2), ppm 1002 880 141 159 Arsenic (As), ppm 118 109 92 88 Sodium (Na), ppm 2779 2675 2247 2241 Potassium (K), ppm 544 458 483 404 Calcium (Ca), ppm 18.8 10 36.5 21.7 Magnesium (Mg), ppm 0.57 0.56 0.64 0.61 Iron (Fe), ppm 2.7 1.11 0.11 0.07 Ammonia (NH3), ppm 32 16 20 11 Lithium (Li), ppm 2.99 2.85 2.45 2.47 Bicarbonate (HCO3), ppm 299 242 299 221 Chloride (Cl), ppm 4892 4358 3910 3659 Sulphate (SO4), ppm 69 52 27 28 Fluorite (F), ppm 2.8 1.9 2.7 2.8

PT Geoservices, Bandung, 2004

4. DEVELOPMENT steam dryness is about 45%, which is still lower than the calculated dryness obtained during well production testing, The sub-surface temperatures were ranging from 240°C to 90-95%. Therefore, there is an extra 45% steam to add in 310°C in static condition. It is close to the temperatures to the well BEL-03. It could come from another source at calculated by silica-Na/K geothermometers range from depth of 200 m above sea level down to 400 m below sea 280oC up to 300oC. This static temperature then decreases o level as shown by temperature convective profile, figure to 200-215 C at depth below 400m below sea level during 4A. If this is the case, the high chloride content may source flowing, figure 4A. Hot water has been interpreted flashing from hot chloride zone at deep level, while the extra steam right at depth of 800-900m below sea level where hot may come from the overlying steam zone. It can be chloride water present. The existence of hot chloride water understood then that chloride and silica content are very may also be indicated by high chloride content of the water high. sample (3000 ppm) that taken from weirbox. Most of the samples are on the precipitation zone, since The preliminary results of the chemical analyses of water silica content is higher than the silica (quartz) solubility, samples show high contents of silica (475-1002ppm), of figure 11. Therefore, it can be understood that thin deposit chloride (3000-4000ppm), and of sodium (2000-3000ppm), of silica was visible on the pit along weirbox to pond. The table 2. This may indicate a Bedugul-Bali geothermal very high silica content may raise a problem of deposit system is a water-dominated system. BEL interpreted that when hot geothermal fluids flash into steam phase. BEL-03 has been drilled into the hot chloride water system, Therefore, it is advised to extract steam rather then hot since monitoring chloride content of water in the weirbox is water, suggesting only drilling in the steam zone overlying relatively high and constant, figure 10. It is about 3000ppm the hot water zone. during testing that could be sourced from the hot chloride water system exist at depth. High content of chloride may o There is no doubt that the geothermal system of Bali to be be also due to hot fluids (Testimated=330 C and two-phase system as supported by figure 12. Clestimated=1750ppm) undergo multiple flash steam separation (P=18bar and P=1bar). If this is the case, the 8 Mulyadi et. al

WEIRBOX Chloride MONITORING BEL-03 4,000 WHP = 150psi WHP = 100psi 3,500 WHP = 200psi 3,000 2,500 2,000 1,500 1,000 500 Chloride content, ppm 0

4 4 4 4 4 4 4 4 4 4 4 4 4 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 /2 /2 /2 /2 /2 /2 /2 /2 /2 /2 /2 /2 /2 /2 5 6 7 8 9 0 1 /1 /2 /3 /4 /5 /6 /7 /2 /2 /2 /2 /2 /3 /3 6 6 6 6 6 6 6 5 5 5 5 5 5 5

Cl-contents (09.00) Cl-contents (15.00)

Figure 10: Monitoring chloride content during testing.

SILICA SOLUBILITY

2000

1800

1600

1400

1200

1000

800 Silica, ppm Silica,

600

400

200

0 50 100 150 200 250 300 350 Temperature, °C

SiO2, Amp SiO2, Crist SiO2, Qtz SPW -GS WBS-May14 WBS-GS

W BS-UNUD WBS-May17 SPW-May17

Figure 11: Silica content of weirbox sample and of separated water sample.

Figure 12: Saturated water-steam graphic showing BEL-2 and BEL-3 are on the water zone 9 Mulyadi et. al

The T-P profile of BEL-03 showed convective temperature Well BEL-03 which is only discharging 38t/h steam will be gradient of about 240-260°C at a depth ranging from combined with a new well, which will be expected to fulfill 1400m to 1800m followed by conductive temperature the rest of steam to generate 10 MWe power for 30 years. gradient of 7°C/100m with maximum temperature of The new well is going to be drilled at pad C or G with other 310oC, figure 4A. The figure of convective zone may wells that are used for supplying 3 x 55 MWe power in indicate good permeability and there could be any steam 2005. An injection well is plan at BEL-02, where it is zone at its depth. Unfortunately, the convective zone is about 2 km east of BEL-03. wrapped blind liner 9 5/8”, table 3. Most of the Bedugul geothermal prospect area is covered with natural preserves and protected forests areas. Since Table 3: Casings set in the well BEL-03. then, the directional drillings have been applied to avoid Depth, m them; their pads are at out-siding of the prohibited area. Casing Measured Vertical Some wells shall be used as injection well to flow brine 30" 0 16 0.0 16.0 down to the reservoir zone to avoid negative environment 20" 0 448.3 0.0 446.6 impact. 13 3/8" 371 1656 370.1 1540.0 9 5/8" blind 1409.5 2022.8 1321.3 1853.7 4. PROJECT SOCIALIZATION 9 5/8" perforated 2022.8 2686 1853.7 2391.0 The awareness of the sustaining environment, keep Balinese watching and understanding what is going on with geothermal project. They need electricity, but they do not The energy stored in the rock and its fluids has been want the water of the three lakes and their forest including calculated using Monte Carlo method, ending the value of its habitat at Bedugul decrease due to that project, figure 13, most likely potential of 350 MWe, table 4. and wherever BEL will commit to Bedugul keep sustainable. There will be no doubt to develop total 175 MWe since their energy potential to be about 350 MWe. Part of Bedugul is covered by Holiness Mountains that

2 should not be changing. The Balinese will consistently By having a proven area of 8km , the energy potential will keep equalizing the life and its environment from sea to then be extracted to develop a small-scale power of 10MWe mountain. in next two years, 2006; it will be built other 55 MWe every year starting in 2008 and ending with total of 175 MWe in 2010.

Table 4: Resource calculation using Monte Carlo RESOURCE DATA Parameters Minimum Maximum Most Likely Reserve Estimation, Mwe Area (km2) 30 40 35 Minimum = 135.5 Thickness (m) 800 1100 950 Maximum = 791.3 Rock Porosity 0.08 0.09 0.1 Most Likely = 355.5 Rock Density (kg/m3) 2500 2600 2550 Rock Spec. Heat (kJ/kg.oC) 0.7 0.9 0.8 Initial Temperature (oC) 240 300 270 Initial Water Saturation (%) 60 80 70 P10 = 183.2 Initial Vapor Saturation (%) 40 20 30 P50 = 317.9 Final Temperature (oC) 175 185 180 P90 = 525.0 Final Water Saturation (%) 10 30 20 Final Vapor Saturation (%) 90 70 80 Recovery Factor (%) 12.5 25 18.75 Electical Conversion Factor (%) 10 11 10 Life Time (Year) 29 31 30 Electricity Potential Probability

300 100% 254 90% 250 80% 70% 200 175 60% 150 131 50% 118 98 40% Frequency 100 30% 64 56 Cum. Frequency 39 20% 50 34 21 7 10% 0 0% 136-195 195-255 255-314 314-374 374-434 434-493 493-553 553-613 613-672 672-732 732-791 Electricity Potential Range. MWe Geothermal Lab - ITB

10 Mulyadi et. al

Figure 13: Sustainable protected forest area at the edge of the Bedugul caldera BEL has been extensively introducing the technology of Figure 15: Cultural ceremonial. geothermal energy development to all Balinese since March of 2004. They have been giving them education, 5. CONCLUSION presentations, and workshops. In addition they have The Bedugul geothermal prospect area is very displayed posters at the super markets, villages, schools, comprehensive, and its geothermal reservoir is very deep. communities, and government, figure 14. It was surprising There is a huge amount of energy in sub-surface rocks that Balinese, especially the people who stay in the located within the caldera. surrounding prospect area, will not avoid the geothermal project if the negative environmental impact looks The very thick cap rocks may block the hot fluids flowing relatively low. However, Balinese still are watching the into the surface. This may result in small thermal environmental impact resulted from the geothermal project. manifestations, even though the cap rocks may fracture due There is a small group against the project; some of the to movements. There are other reservoir rocks down at a people misunderstand the geothermal technology and others very deep level. do not want Bali to change. They are still worried and afraid of a change in the environment due to geothermal A small power of 10 MWe will be run before developing development. other large 3 x 55 MWe power for the near future, since the preliminary proven area could reserve approximately 30 BEL suggested that the Bali Environment Institute analyze MWe for 30 years life. the environmental impact of geothermal energy development for above 10MWe. BEL has conducted scientific and Balinese culture study to develop the geothermal energy at Bedugul.

6. SUGGESTIONS BEL is going to perform more work on BEL-03 such as conducting well simulation, running spinner, perforate BEL-03 blind liner to create new feed zone from the reservoir, and down hole sampling, to make apparent the geothermal system in Bedugul, Bali.

BEL is going to pay attention of silica deposit occurrence, since that most of silica content of the samples are on the precipitation zone.

BEL is going to perform more careful gas analyses especially on magmatic gases before running the 10 MWe power.

Figure 14: Exhibition of geothermal energy REFERENCES development at the supermarket. PT Tri Bawana Utama and Geosystem: Magnetotelluric and Time Domain Soundings in the Bedugul area, Bali. The common question posed to BEL is if there will be job BEL-internal report, 1996. vacations for the local community and other advantages. Questions about tourist attractions are also common. ……………….. : The usefulness of non-oil electricity generation to support tourism in Bali, workshop, BEL obeys the traditional customs when scientifically Politeknik Bali, Denpasar, 1997. extracting the energy from the earth. Some ceremonial events are being conducted before work begins in order to Dames and Moore: Fluid chemistry of geothermal surface remember and thank GOD, figure 15. manifestations, Bali geothermal field, final report, BEL-intern report, 1997. Pintak Corporate Communications: Media Audit Phase Two Bali – Based Media, Bali Energy, 1997.

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Mulyadi : Mt-Resistivity evaluation on Bedugul geothermal JETRO-WestJec: Feasibility study on Bedugul geothermal prospect, Bali, BEL-internal report, 2004. development, BEL-intern report, 2004. Bali Energy Limited: Socialization for Bedugul geothermal PT Geoservices: Pressure and Temperature Down Hole developments, BEL, 2004. Measurement in the well BELL-03, BEL-intern report, 2004