PROCEEDINGS, Fourty Workshop on Geothermal Reservoir Engineering
Stanford University, Stanford, California,
January 26-28, 2015
Regional Assesment Using Graphical Techniques of Indonesian Non-Volcanic Geothermal
System In Central Sulawesi, Indonesia: Based on Fluid Geochemistry
Ali Fahrurrozie1, Yosi Amelia1, Andri Eko Ari Wibowo2
1
Geothermal Engineering, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Indonesia
2
Center of Geological Resources, Geology Agency, Ministry of Energy and Mineral Resources, Indonesia
1
alifahrurrozie@gmail.com
Keywords: Na-K-Mg, Na-K, Mg-Ca, K-Mg, Quartz, geothermometer, geochemistry, non-volcanic, Central Sulawesi
ABSTRACT
Indonesia has many geothermal prospects which spreading out in Sumatra, Java, Bali, NTT and Sulawesi Islands. Most of
Indonesian geothermal system is located in Sumatra and Java associated with high temperature system hosted by volcanic rock.
Sulawesi island is different than those. In part of Sulawesi has non-volcanic geothermal systems hosted by granitic and
metamorphic rock. Central Sulawesi has eleven geothermal prospects reported as non-volcanic geothermal system. The geothermal
prospects are still in an exploration stage to get to know their geothermal system properties with geological, geophysical, and
geochemical surveys. Till now, no one of those prospects are developed for electricity or direct use utilization. Some of 3G survey
had been conducted by Center of Geological Resources, Geological Agency, Ministry of Energy and Mineral Resources of
Indonesia. Geochemical surveys are used to get characteristics of fluid geochemistry, either water or gas. Fluid geochemistry, only
water, will be evaluated in this paper to know characteristic of manifestations, type of fluid, and geothermometers. Water
geochemistry are used also to know equilibrium of fluid and understand fluid process in either deep or shallow levels. Reservoir
temperature by geothermometers not just one objective in analysis of water geochemistry. Whereas, the important thing is deduce
deep temperature with considering water-rock interaction or fluid-rock equilibration.
In this paper, the application of Na-K-Mg ternary, Na-K/Mg-Ca and K-Mg/Quartz diagram are applied to compare temperature
equilibration each other, to consider the equilibrium of fluid, and to analyze some processes in either deep or shallow level of seven
non-volcanic geothermal systems in Central Sulawesi, Indonesia. The seven non-volcanic geothermal systems, namely Tambu,
Ranang, Lompio, Marana, Bora, Pulu, and Kadidia. The methods have been applied in some volcanic geothermal systems in New
Zealand such as Waiotapu and Rotorua and Alto Peak geothermal field in Philippines. The K-Mg/Quartz diagram is consist of two
low temperature geothermometers. These geothermometers can eliminate invalidity of each geothermometer, which could be
caused by dilution process, equilibration with amorphous silica, or some residual effect of an acid zone. The Na-K/Mg-Ca diagram
also has two geothermometers, Na-K geothermometer with equilibration of the system Mg-Ca. Both of them usually use to know
the influence of shallow and low temperature processes. Na-K-Mg ternary diagram consist of fast-responding K-Mg with slowly reequilibrating Na-K geothermometers to evaluate degree of attainment of fluid-rock equilibration. This ternary plot is powerful tool
to keep water distinct between water suitable and unsuitable for the application of ionic solute geothermometers, to assess deep
equilibrium temperature, and evaluate re-equilibrium and mixing effect on large number water samples.
The results of study show that almost half of thermal springs attaint to full equilibrium line, although some of them plotted in
partial equilibrium. These water of thermal springs are in part came from reservoir and in part undergone dilution or mixing
processes. Three graphical techniques were showing the shallow and deep temperature of each prospect with some explanation
about equilibrium and processes of fluids rise from deep to surface. Overall, equilibrium temperatures are taken and proposed from
three graphical techniques as above for the whole set of Tambu discharges with temperature of 140-150°C, Lompio range of
temperature of 210-220°C, Ranang-Kasimbar of 130°C, Bora temperature average of 210°C, Pulu temperature of 230-240°C and
Sapo-Kadidia temperature of 230°C. Only temperature of Marana is unreliable. Equilibrium temperatures as discussed for those
prospects, probably just define shallow conditions before thermal discharges appear in surface. In shallow levels, temperature of
equilibrium is 120-140°C for Tambu, 130°C for Ranang-Kasimba, 210-220°C for Lompio, while others are unreliable.
1. INTRODUCTION
Sulawesi has a large geothermal potential after geothermal potential of Java and Sumatera in Indonesia. The number of geothermal
potential in Sulawesi is 3126 MWe. Whereas, geothermal installed capacity of Sulawesi only 60 MWe in Lahendong Geothermal
Field in North Sulawesi operated by Pertamina Geothermal Energy. The potential of Sulawesi is consist of speculative resources of
1345 MWe, hypothetical resources of 179 MWe, possible reserve of 1374 MWe, probable reserve of 150 MWe, and proven reserve
of 78 MWe (Center of Geological Resources, 2013). A large number of geothermal system in Sulawesi is associated with a
Quarternary andesitic volcanoes, Tertiary andesitic volcanoes, and predominantly non-volcanic geothermal system. Approximately,
thirty two (32) of fifty (50) prospects in Sulawesi is non-volcanic geothermal system (Wibowo, 2014). Most of non-volcanic in
Sulawesi is located in Central Sulawesi, fourteen prospects. Hence, on this paper we are going to discuss about a half prospect of
them to do regional assessment of Indonesian non-volcanic geothermal system, particulary in Central Sulawesi as representative of
non-volcanic system in Sulawesi and generally in Indonesia.
Previous study on non-volcanic geothermal system in part of center of Sulawesi by Yushantarti, et al (2012) described many
prospects of Central Sulawesi, West Sulawesi and South Sulawesi. Furthermore, they only explained the geochemical properties of
each manifestation without give detail explanation about fluid process from deep to surface, temperature equilibration with
considering water-rock interaction or fluid-rock equilibration. The objective of investigation is evaluate and asses through water
1
Fahrurrozie, et al.
geochemistry the equilibrium of the fluid in regional area of Central Sulawesi. The paper clarify about fluid process, temperature
equilibration with considering water-rock interaction or fluid-rock equilibration which not discussed on Yushantarti’s paper.
Several prospects will be analyze and discuss on this paper are Tambu, Ranang, Lompio, Marana, Bora, Pulu, and Kadidia (See
Figure 1). Since in late’s 80 and early 90 years, Giggenbach (1986), Giggenbach (1988), Giggenbach and Glover (1992),
Giggenbach, et al (1994) started to present equilibrium concepts to evaluate water geochemistry, many geochemical evaluation of
obtained result from geochemical survey must considering it to get a good interpretation of geochemical characteristics of a
geothermal system. However, analyzing of geochemical data in many geothermal prospects conducted by geochemist or
geoscientist never used to the graphical techniques. However, these graphical techniques can be inferred give a good, reliable and
accurate result if gas geochemistry data is not available. So, in this paper we are going to use the equilibrium concepts to do
regional assessment in Central Sulawesi, Indonesia. Hoping this idea will be used to understand characteristics of geothermal
system and geothermal potential to facilitate a geothermal development in Central Sulawesi, future.
Figure 1: Map of Geothermal prospects in Central Sulawesi.
2. METHODOLOGY
The whole geochemical properties of each hot or warm spring is obtained result of geochemical survey conducted by Center of
Geological Resources, Ministry of Energy and Mineral Resources on paper of Yushantarti, et al (2012). We are using the data and
Wibowo’s data (Wibowo, 2014) to discuss regional assessment in Central Sulawesi in next section. Geochemical data of fourteen
prospects are selected and eliminated to become only seven (7) prospects or twenty nine (29) manifestations. The availability of
geochemical properties and accuration data is considered to select the good and reliable data. The standard to evaluate water
geochemistry is determine and check value of ionic balance (IB) and type of fluid. Whereas, analyze of conformity between pH,
temperature, type of fluids, and field characteristics of some manifestation also to be consider to get a good geochemical evaluation.
Not only geochemical data will be considered, but also the geological setting of each prospects. For geochemical analysis and
interpretation of hot or warm springs data Indonesian geochemist prefer rely SO4-Cl-HCO3, Na-K-Mg, and B-Cl-Li ternary diagram
and solute geothermometer based on equation. Equation geothermometer cannot recognize fluid equilibrium. Indonesian
geochemists have been thought enough that these diagram and stable isotope diagram can give a comprehensive geochemical
interpretation for each prospect. Actually, graphical techniques are Na-K-Mg, Na-K/Mg-Ca and K-Mg/Quartz diagram can give
more added value to be intrepreted. Deep temperature considering equilibrium, fluid process, and fluid-rock equilibration can be
analyzed by the three graphical techniques.
3. NON-VOLCANIC GEOTHERMAL PROSPECTS AND THEIR GEOCHEMICAL CHARACTERISTICS
As we know above, selected non-volcanic geothermal prospects consist of seven prospects and twenty nine manifestation. A review
of geochemical characteristics for each prospect is given below about the type of fluid, temperature, pH, ionic balance, outflow or
upflow zones and some other characteristics. In this section, knowing geochemical characteristics of theirs non-volcanic geothermal
systems is expected can make us clear to identify system of non-volcanic and can distinguish between common non-volcanic and
common geothermal system, volcanic-hydrothermal system. Fluid type and symbology follow the classification described by
Hochstein et al. (2010) with additional class.
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4. DISCUSSION
4.1 Na-K-Mg Ternary Diagram
Marini (2004) did explain Na-K-Mg diagram can assess deep equilibrium temperature and evaluate re-equilibrium and mixing
effects on a large number of water samples. The diagram have three area are a full equilibrium, partial equilibrium, and immature
waters. Commonly, the diagram can decide temperature for shallow by fast-responding K-Mg system (TK-Mg) and deep reservoir by
slowly re-equilibrating Na-K system (TNa-K). Almost a half discharge points of twenty nine discharges plotted in partial
equilibrium. It is remarkable pattern for a large number water samples. This unique pattern probably is caused by a great factor
such as a large geological structure in an extensive geothermal area. Typically, almost discharges plotted in immature water like the
rest discharge points in immature waters area and close to the Mg corner (see Figure 3). So, their Na-K temperatures have lower
reliability (Giggenbach, 1988). The following chloride and chloride-bicarbonate water discharges points in partial equilibrium are
Tambu, Roras, and Ponggerang (Tambu prospect); Lompio-1, 3 and Ombo (Lompio); Koala Rawa (Sapo-Kadidia); Ranang-1 and
Ranang-3 (Ranang Kasimba); and Bora (Bora). Whereas, discharge points in partial equilibrium also are Kadidia, Sejahtera-2
(Sapo-Kadidia prospect); Kaliburo, Mapane, Pulu-1 (Pulu); and Lambani (Ranang Kasimba) which are bicarbonate and
bicarbonate-chloride waters type. No one has discharge point to attain full equilibrium line.
Figure 2: SO4-Cl-HCO3 Ternary Diagram (Giggenbach, 1988) of samples of Central Sulawesi Geothermal Prospects.
Samples name follow Table 1.
Figure 3: Na-K-Mg Ternary Diagram (Giggenbach, 1986) of samples of Central Sulawesi Geothermal Prospects. Samples
name follow Table 1. Type of fluid follows the classification described by Hochstein et al. (2010) with additional class.
Assigning temperature (TNa-K) can be assumed for all prospects, except Marana. None of its discharge has point to attain the
equilibrium area even partial equilibrium. So, temperature for Marana prospect is assumed from low temperature, T K-Mg of around
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Fahrurrozie, et al.
100C. It just can describe conditions at shallow levels and can be applied. While, a deep temperature of Marana can not be
assumed by Na-K-Mg diagram. Refer to each discharge on Figure 3, TNa-K of around 240C for Kaliburo (Pulu); 230C for Mapane
(Pulu) and Koala Rawa (Sapo-Kadidia); 210C for Lompio-1, 3 (Lompio) and Bora (Bora); 180C for Ombo (Lompio); 150C for
Tambu (Tambu); and around 80-100C for Ponggerang (Tambu), Ranang-1 and 3 (Ranang Kasimba), Sejahtera-2 (Sapo Kadidia),
Pulu (Pulu), Kadidia (Sapo-Kadidia), Roras (Tambu), and Lambani (Ranang Kasimbar) thermal discharges. There is an interesting
fact that high TNa-K for a large number water sample on this paper is neutral-bicarbonate type water such as Kaliburo and Mapane.
Its mean fluid both of them still able to maintain equilibrium condition from deep to surface, although mixing process probably
occurred. Its surface temperature can prove the fact. Kaliburo and Mapane discharges have temperature of 84.80C and 94.20C.
On the contrary, some of neutral pH NaCl type water such as Masaingi and Merana-2 discharges plotted far from the equilibrium
line, not having even a partial equilibrium. Their high Mg content suggests a water-rock interaction process to reflect an immature
nature of the water (dilute water), possibly affected by the absorption of dissolved rock (Reyes et al., 1993). Merana-2 has a highest
Mg value around 14.88 mg/kg, while Masaingi has 5.94 mg/kg of Mg. Refer to Figure 3, a T K-Mg of around 200C for Koala Rawa
(Sapo-Kadidia), 190C for Mapane (Pulu), 170C for Lompio-1, 3 (Lompio) and 140C for Tambu (Tambu), and around 80C for
Ponggerang, Roras (Tambu), Ranang-3, Ranang-1, Lambani (Ranang-Kasimbar), Pulu-1 (Pulu), and Sejahtera-2 (Sapo-Kadidia).
Mg can respond faster to decreasing temperature than Na, thus TK-Mg in shallow levels is still reliable to be applied (Giggenbach,
1986).
4.2 Na-K/Mg-Ca Diagram
Most of water discharges from Lompio (Lompio-1, 3 and Ombo), Ranang-Kasimba (only Lambani and Ranang-3), Tambu (Tambu,
Ponggerang) have equilibrated fluids (Figure 4). While, thermal discharges plotted close to equilibrium line such as Kadidia, Pulu1, Masaingi and Kaliburo. Rock dissolution by acidic condensate or magmatic constituent can bring several cations such as Na, K,
Mg, and Ca which dissolved to geothermal fluids. Intensive interaction for a long time between fluids and host rocks will produce a
equilibration on geothermal fluids. The point marked “rock dissolution” in Figure 4 with x= 0.8 and y=0.8 is based on several
averages of x= 10 K/(10 K +Na) and y= 10 Mg/(10 M+Ca) ratios for the mean x and y ratio of dissolved volcanic rocks, including
Sibalaya-2 springs. However, neutral pH and bicarbonate type of fluid is still doubtful, but it has highest value of Mg (9.86 mg/kg)
probably can prove the fact that rock dissolution occurred on fluid till appears in surface as this thermal discharge in Bora prospect.
On the other hand, a neutral pH sulphate of Sidera discharge plotted far from point of rock dissolution. Its means the fluid is
completely neutralized by the reaction with host rocks. Rock dissolution in highly immature water generally is caused by volcanic
waters (Reyes et al., 1993).
Figure 4: Plot of 10 K/(10 K+Na) versus 10 Mg/(10 Mg+Ca), Ci in mg/kg or Na-K/Mg-Ca Diagram (Giggenbach and Glover,
1992, modified) of some thermal discharges in Central Sulawesi geothermal prospects. For sample names see Table
1. Type of fluid follow the classification type as described by Hochstein et al. (2010) with additional class.
As we know, Na-K system shows water-rock equilibration temperatures to reflect conditions at deeper levels. Combination of
Mg and Ca can indicate a mixing with lower temperature aquifers, steam heating or oxidation process. Magnesium (Mg) is a key
to know a mixing, steam heating and oxidation process, because the process are involving shallow water or groundwater which
contain more magnesium than geothermal fluid from reservoir. Data point for Koala Rowa, Sejahtera-2, 4, Walatana, Bayosa, and
Yampo-1 show high Mg/Ca ratios corresponding to rock dissolution followed by deposition of K-rich secondary minerals such as
clays and zeolites like laumontite at low temperatures (Giggenbach et al., 1994). The point marked at x=0.28 and y=0.95 represents
“seawater”. The point marked at x=0.28 and y=0.95 represents “seawater”. Yompo and Bayosa (Marana prospect) samples are near
this point. Neutral pH chloride water of Merana-2 is close to both of them. Probably sediment or connate water affected the fluid of
thermal discharges. The whole set of water are HCO3 -water as suggested by Figure 2, which rises to the surface slowly. The cluster
in Figure 4 is related to neutral pH, Na-Cl type waters and bicarbonate-chloride water (Masaingi, Kaliburo, Mapane, and Bora)
which not attain to the equilibrium line but just had been re-equilibrated, so these waters plot in a transition area from rock
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Fahrurrozie, et al.
dissolution to rock-fluid equilibrium. Respond to change is shown by general trend line. Overall, equilibrium temperatures
estimated using Na-K/Mg-Ca geothermometer are 120-140°C for Tambu, 130°C for Ranang-Kasimba, 210-220°C for Lompio, and
uncertain temperature for Marana, Bora, Pulu, Sapo-Kadidia, because their samples not attain equilibrium. However, reequilibrated did occure.
4.3 K-Mg and Quartz (Conductive) Diagram
As discussed in the previous subsection, K-Mg/Quartz (conductive) diagram can only provide low temperature estimates. This
diagram was compared to low temperature geothermometers to eliminate invalidity of each geothermometer, which could be
caused by dilution process, equilibration with amorphous silica or some residual effect of an acidic zone (Powell and Cumming,
2010). The chemical system between K-Mg and dissolved silica can respond fast to temperature changes. Condensate water are
found in Yompo-1, 2, Bayosa (Marana), Sejahtera-1, 2, 4, and Kadidia (Sapo-Kadidia), Sibalaya-1, 2, and Sidera (Bora), Walatana
and Pulu-1 (Pulu), Budi Mukti (Tambu), Ranang-1 (Ranang Kasimba). While, Koala Rawa (Sapo-Kadidia), Tambu, Ponggerang,
and Roras (Tambu), Lompio-1, Lompio-3, and Ombo (Lompio), Mapane and Kaliburo (Pulu), Ranang-3 (Ranang-Kasimba) are
outflow discharges. Bora (Bora), Masaingi and Merana-2 (Marana) are another group which plot between amorphous silica and the
equilibrium line. The reason is probably due to an extensive water-rock interaction process during fluid rise to the surface for
Merana-2. Merana-2 thermal waters has aqueous silica concentrations which are controlled by saturation with silica polymorph
(amorphous silica is the most soluble silica polymorph) of intermediate solubilty (Marini, 2004). Data points for Kaliburo (Pulu)
move to downwards because a loss of silica and disequilibrium or re-equilibrium as shown in Figure 4. Condensate water has
equilibrated with amorphous SiO2 with a temperature of equilibrium between <70°C. Another group is outflow discharges in
equilibrium with chalcedony with equilibrium temperatures between 90 and 200°C. Overall, equilibrium temperatures are taken and
proposed as K-Mg and silica geothermometer of 180-200°C for Pulu, 185°C for Sapo-Kadidia, 155-165°C for Lompio, 125°C for
Tambu, and 85°C for Ranang-Kasimba. Whereas for others is unreliable.
Figure 5: Plot of log (K2/Mg) versus log (SiO2) (Giggenbach and Glover, 1992) of some thermal discharges in Central
Sulawesi geothermal prospects. Sample name follow Table 1. Type of fluids follows the classification described by
Hochstein, et al. (2010) with additional class.
5. CONCLUSION
Almost ten thermal discharges in Central Sulawesi are coming from reservoir. Dilution and mixing process are becoming an
dominan process for others thermal discharges. While, extensive interaction with surrounding rock only occurred for Merana-2
(Marana). Thermal waters that come from a reservoir fluid with a small effect of dilution or mixing are found in Koala Rawa
(Sapo-Kadidia), Tambu, Ponggerang, and Roras (Tambu), Lompio-1, Lompio-3, and Ombo (Lompio), Mapane and Kaliburo
(Pulu), Ranang-3 (Ranang-Kasimba). Water-rock equilibrium is an important aspect to be considered to produce a reliable and
acceptable reservoir temperature estimate. Closer the fluids are to equilibrium conditions, more reliable are our estimates of deep
and shallow process of fluids. Thus, thermal water can be estimated correctly and accurately. A combination of three graphical
techniques (Na-K-Mg, Na-K/Mg-Ca, and K-Mg/Quartz) gives less uncertainty about the use of geothermometers to be applied
confidently in geothermal resources assessment of Cecntral Sulawesi prospects. These graphical techniques are more reliable than
equation solute geothermometers to the assessment of reservoir temperature and hence for determine geothermal potential. These
techniques consider processes of fluid from reservoir to surface, while equation geothermometers just give results without consider
subsurface process. Overall, equilibrium temperatures are taken and proposed from three graphical techniques as above for the
whole set of Tambu discharges with temperature of 140-150°C, Lompio range of temperature of 210-220°C, Ranang-Kasimbar of
130°C, Bora temperature average of 210°C, Pulu temperature of 230-240°C and Sapo-Kadidia temperature of 230°C. Only
temperature of Marana is unreliable. Equilibrium temperatures as discussed for those prospects, probably just define shallow
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Fahrurrozie, et al.
conditions before thermal discharges appear in surface. In shallow levels, temperature of equilibrium is 120-140°C for Tambu,
130°C for Ranang-Kasimba, 210-220°C for Lompio, while others are unreliable.
Table 1: Chemical analyses of selected water samples from geothermal prospects in Central Sulawesi (all concentrations in
mg/kg). Samples name cited is listed by capital T, L, M, R, B, P, S in column 2 which refer to T: Tambu, L: Lompio, M:
Marana, R: Ranang-Kasimbar, B: Bora, P: Pulu, S: Sapo-Kadidia. Type fluid symbol: c: chloride, s: sulfate, b:
bicarbonate, c-s: chloride-sulfate, and b-s: bicarbonate-sulfate water.
Samples
T
(°C)
pH
Na+
K+
Ca2+
Mg2+
Cl-
HCO3-
SO42-
SiO2
Fluid
type
IB
(%)
7.25
199.99
61.46
c
3.34
Tambu
T. Tambu
57.40
7.10
1226.00
29.00
760.90
1.00
3339.44
T. Roras
39.70
6.68
374.60
8.70
190.40
5.40
909.17
97.83
3.00
41.95
c
1.58
T. Budi Mukti
34.20
7.50
51.90
3.09
16.90
3.42
3.00
195.66
5.00
34.27
b
0.96
T. Ponggerang
45.20
7.04
337.10
3.88
59.20
0.22
594.46
1.91
57.61
34.06
c
0.74
Lompio
L. Lompio 1
78.10
8.15
1702.00
140.40
813.20
4.17
3900.00
29.50
165.00
127.00
c
1.98
L. Lompio 3
72.80
8.15
1680.00
133.00
787.80
3.99
3827.61
27.50
172.00
126.00
c
1.80
L. Ombo
51.80
7.04
2962.00
148.60
850.80
2.70
5800.94
288.50
300.00
150.00
c
0.20
Marana
M. Bayosa
59.10
8.10
104.96
4.54
10.69
5.95
34.89
142.85
110.74
116.19
b-s
0.65
M. Yompo 1
55.60
8.00
100.96
3.15
8.96
5.95
17.44
157.59
102.55
110.28
b-s
1.87
M. Yompo 2
50.10
7.90
95.78
3.02
7.96
5.95
14.89
165.32
91.02
90.44
b-s
1.04
M. Masaingi
90.00
7.40
328.70
34.86
148.80
5.95
726.06
37.40
104.11
132.51
c
0.34
M. Merana 2
54.00
8.00
291.69
12.17
74.40
14.88
567.62
75.99
25.00
110.82
c
0.44
Ranang-Kasimbar
R. Ranang 1
61.80
9.42
83.90
1.31
0.75
0.16
59.58
40.46
39.50
52.97
c-s
8.22
R. Ranang 3
55.70
9.27
133.80
2.64
6.70
0.13
165.77
32.57
56.79
59.46
c
1.27
R. Lambani
55.60
8.78
64.67
0.06
3.44
0.20
7.50
102.06
15.39
65.37
b
15.3
B. Bora
90.10
7.22
550.80
46.40
53.10
4.62
743.96
360.36
88.06
149.53
c
0.97
B. Sidera
37.80
7.81
67.40
2.04
33.00
4.82
49.40
168.81
387.68
43.06
s
41.7
B. Sibalaya 1
37.40
7.50
36.82
3.40
50.70
9.75
14.00
223.76
25.00
37.86
b
4.56
B. Sibalaya 2
35.70
7.52
31.70
8.80
63.86
9.86
49.40
189.11
28.81
38.46
b
4.76
Bora
Pulu
P. Pulu 1
75.70
8.60
80.00
2.00
2.60
0.09
27.91
81.72
40.00
75.60
b
10.7
P. Mapane
94.20
8.10
552.86
57.14
2.26
0.19
454.90
618.20
68.00
195.29
b-c
2.52
P. Kaliburo
84.80
8.20
540.32
57.14
1.26
0.05
416.11
618.52
49.30
201.49
b-c
4.44
P. Walatana
41.50
7.20
52.42
3.93
14.69
8.27
6.00
181.12
30.00
42.40
b
0.42
Sapo-Kadidia
S. Sejahtera 1
51.00
6.97
95.12
2.57
7.86
1.78
82.45
150.00
6.00
54.94
b
1.73
S. Sejahtera 2
62.80
8.41
87.13
2.12
0.31
0.12
59.53
82.68
27.04
58.34
b-c
3.65
S. Sejahtera 4
57.40
7.75
64.24
2.78
1.83
0.77
6.00
160.85
12.00
42.39
b
0.58
S. Kadidia
81.40
8.32
128.30
2.80
2.19
0.10
102.45
112.86
40.44
65.37
b-c
1.66
S. Koala Rawa
104.1
8.75
399.00
42.51
0.17
0.08
460.89
220.30
37.04
266.07
c
3.00
ACKNOWLEDGMENTS
We are thankful to Center of Geological Resource, Geological Agency, Energy and Mineral Resources, for providing us data which
are used for supporting this paper. The authors also would like to acknowledge lecturers and staffs of Geothermal Engineering
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Fahrurrozie, et al.
Master Degree, Faculty of Mining and Petroleum Engineering, Institute Technology of Bandung (ITB) and Indonesia Geothermal
Center of Excellence (iGCoE).
REFERENCES
Wibowo, A.E.A: Karakteristik Fluida Panas Bumi Non Vulkanik Di Pulau Sulawesi Dan Pemanfaatannya Untuk Pembangkit
Listrik Dengan Siklus Kalina, Magister Thesis, FTTM, Institute Technology of Bandung, Bandung (2014) (unpublished).
Center of Geological Resources, Geological Agency, Ministry of Energy and Mineral Resources: Geothermal Area Distribution
Map and Its Potential in Indonesia, scale 1:5.000.000 (2013).
Giggenbach,W.F.: Graphical techniques for the evaluation of water/rock equilibration conditions by use of Na, K, Mg, and Ca
contents of discharge waters, Proceedings, 8th NZ Geothermal Workshop, Auckland, (1986).
Giggenbach, W.F.: Geothermal solute equilibria. Derivation of Na-K-Mg-Ca geoindicators. Geochim. Cosmochim Acta 52, 27492765, (1988).
Giggenbach, W.F., and Glover., R.B.: Tectonic Regime and Major Processes Governing The Chemistry of Water and Gas
Discharges From The Rotorua Geothermal Field, New Zealand, Geothermics, Vol 21, (1992), 121-140.
Giggenbach, W.F., Sheppard, D.S., Robinson, B.W., Stewart, M.K., and Lyon, G.L.: Geochemical Structure and Position of The
Waiotapu Geothermal Field, New Zealand, Geothermics, Vol 23, (1994), 599-644.
Herdianita, N.R., Situmorang, J., Mussofan, W., and Hamzah, I.: Geothermal Resource of Java, Proceedings, Australian
Geothermal Energy Conference, Melbourne (2012).
Hochstein, M.P., Simanjuntak, J., and Sudarman, S.: Geothermal Prospects of the Eastern Banda Arc Islands (Indonesia),
Proceedings, World Geothermal Congress, Bali, Indonesia (2010).
Powell, T., and Cumming, W.: Spreadsheets For Geothermal Water and Gas Geochemistry, Proceedings, 35th Workshop on
Geothermal Reservoir Engineering, Stanford University, Stanford, California (2010).
Reyes, A. G., Giggenbach, W. F., Saleras, J. R. M., Salonga, N. D. and Vergara M. C.: Petrology and geochemistry of Alto Peak, a
vapor-cored hydrothermal system, Leyte Province, Philippines. Geothermics, Vol. 22, (1993), 479-519.
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