Geothermal exploration in Indonesia based on Mineralogy and Hydrothermal Alteration

Fiorenza Deon,Caroline Lievens,David Bruhn,Tia Den Hartog,Franziska Wilke,Yunus Daud,Christoph Hecker,Auke Barnhoorn,Oona Appelt,Tulus Imaro,Besteba Sibarani,Freek Van Der Meer,Chiel Welink,Riskiray Ryannugroho,Ehsan Reyhanitash,Rizki Hutami

doi:10.1088/1755-1315/254/1/012002

Abstract

Indonesia with its large, but partially unexplored geothermal potential is one of the most interesting and suitable places in the world to conduct geothermal exploration research. This study focuses on geothermal exploration based on fluid-rock geochemistry/geomechanics and aims to compile an overview on geochemical data-rock properties from important geothermal fields in Indonesia. The research carried out in the field and in the laboratory is performed in the framework of the GEOCAP cooperation (Geothermal Capacity Building program Indonesia-the Netherlands). The application of petrology and geochemistry accounts to a better understanding of areas where operating power plants exist but also helps in the initial exploration stage of green areas. Because of their relevance and geological setting geothermal fields in Java (Wayang Windu, Tanguban Perahu) have been visited so far. Mount Salak, Gunung Slamet (Java) and Flores surveys are planned in the near future. Operators, universities and governmental agencies will benefit from this approach as it will be applied also to new green-field terrains. By comparing the characteristics of the fluids, the alteration petrology and the rock geochemistry we also aim to compile an overview of the geochemistry of several geothermal fields in Indonesia. The gathering of this information is the base for the geomechanical experiments on-going at TUD. At the same time the rock petrology and fluid geochemistry will be used as input data to model the reservoir fluid composition along with T-P parameters with the geochemical workbench PHREEQC. The field and laboratory data are mandatory for both the implementation and validation of the model results. If successful, this approach can be applied in many geothermal fields characterized by steep terrain and tropical vegetation, which hampers the classical seismic-geophysical exploration methods.

Highlights

In a conventional approach, several methods need to be adopted and integrated to understand the geochemical and geophysical signatures of active geothermal systems [12]
By comparing the characteristic of the fluids, the alteration petrology and the rock we aim to contribute to compile an overview of the geochemistry in the important geothermal fields in Indonesia and to characterize the rocks for the geomechanical experiments on-going and planed at TUD
Rocks The X-ray Diffraction (XRD) semi-quantitative (Figure 3 a and b) interpretation results of the analyzed rocks are listed in table 1

Summary

Introduction

Several methods need to be adopted and integrated to understand the geochemical and geophysical signatures of active geothermal systems [12] These methods apply for green-field studies and include: (a) geochemical investigations (e.g., using chemical geothermometers to infer the temperature of the geothermal reservoir and measurements of gas isotopes, such as 3He/4He, to constrain the origin (mantle or crust) of fluids; (b) drilling of exploration wells; (c). Young volcanic zones along convergent plate margins are prime targets for the exploration of geothermal-energy sources as active magma chambers have an intrinsically geothermal potential [1] Heath transfer in those areas is dominated by circulating fluids and, in the case of two-phase systems, by steam. Geological formations serving as barriers or seals for fluids may prevent discharge of up-flowing waters

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Discussion

Conclusion