Interstratified Illite/Montmorillonite in Kamojang Geothermal Field, Indonesia

D. F. Yudiantoro, E. suparka, S. Yuwono, I. Takashima, D. Ishiyama, Y. Kamah, J. Hutabarat


DOI: 10.17014/ijog.v8i4.167

Kamojang geothermal field located in West Java Province, falls under the Pangkalan Subregency, Bandung Regency. The researched area is a geothermal field located in the Quaternary volcanic caldera system of about 0.452 to 1.2 Ma. The volcanic activity generated hydrothermal fluids, interacting with rocks producing mineral alteration. The minerals formed in the areas of research are interstratified illite/montmorillonite (I/M). Analyses to identify interstratified I/M have been performed by X-ray diffraction using ethylene glycol, while the determination of the type and percentage of interstratified I/M was based on the calculation method of Watanabe. The methodology was applied on core and cutting samples from Wells KMJ-8, 9, 11, 13, 16, 23, 49, 51, and 54. The result of analysis of the samples shows that the type of clay is interstratified illite/montmorillonite and the minerals are formed at temperatures ranging from 180 to 220° C. The type of interstratified I/M in the studied area is S = 0 and S = 1. The percentage of illite type S = 0 is between 20 - 35% illite, whereas type S = 1 has about 45 - 72% illite. Along with the increasing depth, the percentage of illite is getting greater. This is consistent with the vertical distribution of temperature which increases according to the depth. This correlation results in an interpretation that the upflow zone of the geothermal reservoir is located in the centre of the Kamojang geothermal field.


geothermal; Kamojang; fluid; illite; montmorillonite; interstratified


Browne, P.R.L., 1978. Hydrothermal Alteration in Active Geothermal Fields. Earth Planet Set, p.229-250. DOI:10.1146/annurev.ea.06.050178.001305

Inoue A., Bouchet A., Velde B., and Meunier A., 1989. Convenient Technique For Estimating Smectite Layer Percentage in Randomly Interstratified Illite/Smectite Minerals. Clays and Clay Minerals 37, p.227-234. doi:10.1346/ccmn.1989.0370305

Inoue A., 1995. Formation of Clay Minerals in Hydrothermal Environments. In: Bruce Velde (ed.), Origin and Mineralogy of Clay. Springer-Verlag, 334pp. doi:10.1007/978-3-662-12648-6_7

Kamah, Y., Tavip, D., and Agus, A.Z., 2003. Penanggulangan Problem Geologi Dalam Operasi Pemboran Sumur Di Blok Timur Area Geothermal Kamojang Jawa Barat Indonesia. Proceedings of 6th Indonesian Geothermal Association, p.175-184.

Moore, D.M. and Reynolds, R.C.Jr., 1997. X-Ray Diffraction and the Identification and Analysis of Clay Minerals. Oxford University Press, Inc.378pp.

Meunir, A., 2005. Clays. Springer, 472pp.

Pertamina, 2010. Pengukuran Temperatur dan Tekanan. Laporan internal.

Purba, S., 1994. Hydrothermal Alteration of Core and Cutting Samples From Wells KMJ-48 and 53 Kamojang Geothermal Field West Java Indonesia. 58pp.

Rettke, R.C., 1981. Probable Burial Diagenesis And Provenance Effects On Dakota Group Clay Mineralogy. Denver Basin. Journal of Sedimentary Petrology, 51, p.541-551. doi:10.1306/212F7CCF-2B24-11D7-8648000102C1865D

Robert, D., Raharso, R., and Bastaman S., 1983. Exploration and Development of the Kamojang Geothermal Field. Proceedings of IPA, p.171-190.

Srodon, J., 1980. Precise Identification of Illite/Smectite Interstratified by X-ray Powder Diffraction. Clays and Clay Minerals, 28, p.401-411. doi:10.1346/ccmn.1980.0280601

Srodon, J., 1981. X-ray Identification of Randomly Interstratified Illite-Smectite in Mixtures With Discrete Illite. Clays and Clay Minerals.16, p.297-304. doi:10.1180/claymin.1981.016.3.07

Steiner, A., 1968. Clay Minerals in Hydrothermally Altered Rocks at Wairakei. New Zealand. Clays and Clay Minerals. 16, p.193-213. doi:10.1346/ccmn.1968.0160302

Utami, P., and Browne P.R.L., 1999. Subsurface Hydrothermal Alteration in the Kamojang Geothermal Field West Java Indonesia. Proceedings 24th Workshop on Geothermal Reservoir Engineering.

Utami, P., 2000. Characteristics of the Kamojang Geothermal Reservoir (West Java) as Revealed By Its Hydrothermal Alteration Mineralogy. Proceedings World Geothermal Congress, p.1921-1926.

Watanabe, T., 1981. Identification of Illite/Montmorillonite Interstratifications bay X-ray Powder Diffraction. Journal of Mineral Society of Japan, Special Isseu. p.97-114. doi:10.2465/gkk1952.15.Special_32

Watanabe, T., 1988. The Stuctural Model of Illite/Smectite Interstratified Minerals And The Diagram For Its Identification. Clay Science, 7, p.97-114.

Weir, A.H., Ormerod, E.G., and ElManasey, I.M.I., 1975. Clay Mineralogy of Sediments of The Western Nile Delta. Clay Mineral 10, p.369-386. doi:10.1180/claymin.1975.010.5.04

Yudiantoro, D.F., 1997. Kimia Batuan Ubahan Hidrotermal Sumur KMJ- 49 dan Sumur KMJ-57 Lapangan Panasbumi Kamojang Jawa Barat. Tesis Magister Program Studi Teknik Geologi ITB Bandung, 146 pp.

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