Proceedings of the 6th Asian Geothermal Symposium, Oct. 26-29, 2004 Mutual Challenges in High- and Low- Temperature Geothermal Resource Fields, 21-24

AN UPDATE OF -SEMPORNA GEOTHERMAL RESOURCES POTENTIAL, ,

Kamaludin HASSAN Department of Minerals & Science, , Sabah, Malaysia e-mail: [email protected]

ABSTRACT

This short paper updates the thermal water chemistry data of selected Tawau-Semporna hot springs. The significance of the Apas Kiri area is stressed.

1. INTRODUCTION

The geothermal resources and potential of the Tawau-Semporna area, in the state of Sabah, have been repeatedly discussed in many reports since the late 80’s. These include: Lim (1988); Sanudin et al., (1990); Lim et al., (1991); Tjia et al., (1992); Liau (2001); Takashima et al (2001); Ang (2002); Lim and Takahashi (2003), Takashima et al (2003) and others. Except for the few later reports, the geothermal information discussed had based on the preliminary geothermal investigations done during the 80’s, which include surface water chemistry, aerial photo interpretation, limited petrographical and structural analysis and limited geophysical survey. Most of the reports cited the Apas Kiri, Tawau, geothermal manifestation as having the best prospect especially for electricity generation.

Despite the fact that recommendations were put forward to further assess the geothermal characteristics of the Apas Kiri area, the progress has however been quite slow. Nonetheless in 2003-2004 and with IAEA assistance, isotope and thermal water samples were collected and analysed. The samples were collected mainly from the Apas Kiri areas, Tawau hotspring and Sungai Jepun locations. This paper presents the latest chemical results of the resampled thermal waters from the few selected localities of the Tawau-Semporna geothermal sites. Meanwhile, the isotope results are yet to be received.

2. THERMAL WATER RESULTS

From the earlier works done (Lim, 1988; and Lim, Intang and Chan, 1991), the chemistry of the thermal waters and the subsurface temperatures calculated from geothermometers are respectively shown in Tables 1 & 2. The results of the recent water analysis are shown in Table 3. Generally, a similar trend of the thermal water properties between the earlier and the present results is observed from the areas sampled.

The chemistry of the thermal waters indicates that the Apas Kiri area and the Tawau hotspring are neutral sodium chloride water while the Sungai Jepun areas acid sulphate waters. The Apas Kiri area suggests the thermal waters are from a common geothermal fluid source.

3. CONCLUSIONS

The Apas Kiri 5 area shows the best geothermal potential among the areas investigated (Zhonghe Pang, personal communication). Chemical geothermometry shows subsurface temperature as high as 233ºC in the area. Geothermal reservoirs with temperature range of 150-200ºC may also exist in the other areas.

A more focused study, which includes detailed geologic and structural mapping, geophysical surveys and drilling of exploration wells, needs to be carried out to feasibly ascertain the Apas Kiri geothermal system. The viability of tapping the resource for power generation should be pursued.

REFERENCES

Adam, L. (2001) Feasibility of utilising the geothermal resources in the Tawau area, Sabah, Malaysia. Symposium on Geothermal Development in Asia, Tokyo Japan.

21 Proceedings of the 6th Asian Geothermal Symposium, Oct. 26-29, 2004 Mutual Challenges in High- and Low- Temperature Geothermal Resource Fields, 21-24

Ang, N.K. (2002) Electric generation and the prospects of geothermal resources as a renewable energy in the state of Sabah, Malaysia. Proc Asian Geothermal Symposium 2002, Bandung Indonesia: 8. Lim, P.S. (1988) Geology and Geothermal potential of the Tawau area, Sabah. Geol. Surv. Malaysia Annual Report for 1987, 402-413. Lim, P.S. and Takahashi, H. (2003) Possible exploitation of the Tawau geothermal resources in Malaysia. Proc Asian Geothermal Symposium 2003: 44-51. Lim, P.S. Intang F and Chan, F.O. (1991) Geothermal prospecting in the Semporna Peninsula with emphasis on the Tawau area. Geol Soc Mal B 29: 135-155. Sanudin, H.T., Sahat, S, and dan. Dale, B. (1990) Potensi penjelajahan Geoterma di Sabah. Prosiding Persidangan Sains Bumi dan Masyarakat Jul 1990: 129-138. Takashima, I., Azhar, Ahmad, Nazri, Lim, P.S., Koseki, T. and Mori, Y. (2002) Geothermal setting inferred from TL age determination of volcanic and altered rocks at Tawau area, Sabah, Malaysia. Proc Asian Geothermal Symposium 2001: 99-104. Takashima, I., Azhar, Ahmad, Nazri, Lim, P.S., Koseki, T., Mouri and Sucipta IGBE (2003) Preliminary assessment of potentiality of the Quaternary Maria to the Tawau geothermal system, Sabah, Malaysia. Proc Asian Geothermal Symposium 2003: 40-43. Tjia, H.D., Komoo, I., Ali, C.A. and Sanudin, H.T. (1992) Geology of Taman Bukit Tawau, Semporna Peninsula, Sabah. Geol Soc Malaysia B 31: 113-131.

22 Proceedings of the 6th Asian Geothermal Symposium, Oct. 26-29, 2004 Mutual Challenges in High- and Low- Temperature Geothermal Resource Fields, 21-24

Table 1. Chemistry of thermal waters from Tawau, Balung, Apas Kiri & Sungai Jepun areas (modified from Lim, 1991) Samples T1 T2B A4A A4B A1 A5 J1 J2 B1 B2 Site Temp. oC 50.3 31.5 75.6 67.7 60 60 64.9 63.9 55.1 55.6 pH at 25oC 6.9 3.7 6.8 6.7 7.4 6.7 8.6 8.5 6.1 6.0 Dissolved SiO2 8.0 NA 5.0 6.0 6.0 NA 3.0 6.0 NA NA Total SiO2 71 32 88 92 86 75 54 56 37 32 Ca 89.8 138.66 191 179.5 150.9 142.37 317.2 312.4 445.2 447.06 Mg 28.3 14.91 21.4 26.7 34.1 12.9 0.1 0.2 16.4 17.5 K 23.5 3.55 82.5 85 77.5 93.5 3.9 3.8 8.3 9.6 Na 282.7 14 792.5 807.5 760 925 237.5 235 39.25 30.0 Li 1.8 ND 5.6 5.6 5.4 5 0.1 0.1 0.2 0.2 HCO3 444.08 7.32 810.08817.4 705.16 544.12 104.92 97.6 89.06 78.08 SO4 330 500 330 330 312.5 476 900 787.5 1254 1302 Cl 350 6 1350 1400 1250 1410 130 130 10 8 F 1.3 0.23 0.76 0.75 0.65 0.63 1.8 1.8 0.66 0.72 B 20 ND 41 15 21 60 <1 <1 ND ND As 0.75 5 200 250 150 250 ND ND 23.3 17.5 Fe NA 1.4 0.7 1.9 0.3 0.2 ND ND 0.1 0.3 Mn 0.6 0.4 0.9 1.0 0.3 0.8 ND ND 1.1 1.1 Total Solids 1350 644 3422 3396 3158 3446 2026 1996 1846 1834 Na/K 20.5 6.7 16.3 16.2 16.7 16.9 103.6 105.4 6.5 5.2 Na/Ca 5.5 0.18 7.2 7.8 8.78 11.14 1.3 1.3 0.12 0.12 Na/Li 47.5 - 42.6 43.4 42.4 56.1 717.4 730 46.9 45.2 Cl/B 5.3 - 10.05 8.5 10.25 7.17 - - - - Cl/SO4 2.87 0.03 11.09 11.5 6.12 8.03 0.39 0.45 0.02 0.02 Cl/F 144.3 14.17 952 999.7 581.6 1205 38.6 38.6 8.06 5.95

Locality: T1 : Tawau hot spring T2B : Sulphur spring, Upper Tawau River, 3 km from Sabah Park’s Office A4A : Spout at Andrassy old steaming ground A4B : Spout at Andrassy old steaming ground A1 : Outflow of Apas 1 spring (contaminated with cold water seepage) A5 : Hot outlet at Apas 5 mud pool J1 : Main spring Sg. Jepun J2 : Subsidiary spring 10m upstream from J1 B1 : Balung 1 spring B2 : Balung 2 spring

Table 2. Subsurface temperature calculated from Chemical Geothermometers (from Lim et al., 1991) Subsurface Temperature Silica Na/K Na-K-Ca Spring Geothermometer Geothermometer Geothermometer Sample Location Temp.

oC Truesdell Fournier Truesdell Fournier (1975) (1971) (1975) (1971) Truesdell (1975) oC oC oC oC oC T1 5 Km NE Tawau 50.3 118.4 118.9 168.4 201.6 166.5 T2B Upper S. Tawau 31.5 86.6 82.1 315.6 312.3 15.1 A4A Apas Kiri 2 75.6 127.9 130.2 191.9 220.5 190.3 A4B Apas Kiri 2 72.2 129.9 132.6 193.1 221.4 191.9 A1 Apas Kiri2 69.0 126.9 128.9 189.6 218.7 190.6 A5 Apas Kiri3 60.0 120.8 121.7 188.7 217.9 194.4 J1 S. Jepun 64.9 106.8 105.7 50.7 99.3 26.2 J2 S. Jepun 64.1 108.3 107.2 49.9 98.5 25.7 B1 S. Balung 55.1 92.0 88.3 285.3 290.9 24.5 B2 S. Balung 55.6 86.6 82.1 359.6 342.2 25.7

23 Proceedings of the 6th Asian Geothermal Symposium, Oct. 26-29, 2004 Mutual Challenges in High- and Low- Temperature Geothermal Resource Fields, 21-24

Table 3. Chemistry of thermal waters from Tawau, Balung, Apas Kiri & Sungai Jepun areas (from PNOC water analysis test report no. 2004-028) Field T1 A4 A4B A1A A1B A2A A2B A2C A5 J1 J2 Test code Method pH at 25oC 7.69 7.46 7.44 7.56 7.83 7.68 7.69 7.75 8.02 8.22 8.48 1 Li 1.07 4.28 4.18 4.12 4.15 3.66 4.07 4.17 4.73 <0.05 <0.05 3 Na 297 837 838 815 810 716 792 847 858 255 265 3 K 22.6 82.9 81.1 77.9 78.4 88.5 76.2 75.5 86.8 3.77 3.87 3 Ca 125 215 214 212 211 194 208 208 165 322 321 3 Mg 9.15 16.8 16.7 16.7 16.5 14.6 16.1 16.1 13.1 0.18 0.07 3 Cl 353 1246 1237 1196 1218 1078 1213 1231 1336 146 147 2 B 14.2 52.5 52.0 45.5 51.4 46.1 51.1 51.3 55.6 1.39 1.73 2

HCO3 288 606 668 668 649 567 619 627 239 ND ND 2

TCO2 216 468 517 506 481 428 466 469 175 ND ND 2

CO3 N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A ND 2

SO4 338 323 323 312 313 281 315 317 297 1182 1204 4

SiO2 (i) 65.2 77.8 81.8 80.2 81.9 71.1 74.3 69.9 83.1 47.7 49.1 4

SiO2 (ii) 67.0 76.0 79.9 87.0 85.2 67.2 69.0 73.7 76.4 47.1 48.9 4

Locality: T1 : Tawau hot spring A4 : Apas Kiri A4B : Apas Kiri A1A : Apas Kiri A1B : Apas Kiri A2A : Apas Kiri A2B : Apas Kiri A2C : Apas Kiri A5 : Apas Kiri J1 : Sg. Jepun 1 J2 : Sg. Jepun 2

Test Method: 1. pH electrode 2. Titrimetry 3. Atomic Absorption Spectrophotometry 4. Colorimetry

Note: ND = Not detected N/A = Not applicable(no carbonates present; pH<8.25) i = untreated ii = acidified ionic balance range from 0.95–1.04 -2 TCO2 includes all HCO3 and CO3 species expressed as CO2 Results of analysis in mg/l (except pH)

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