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Fluid evolution of Umbul-Telomoyo Geothermal system

2019; IOP Publishing; Volume: 254; Linguagem: Inglês

10.1088/1755-1315/254/1/012003

1755-1307

Hiskia Ulinuha Annisa, Herdianita Niniek Rina, Dudi Hermawan,

Geophysical and Geoelectrical Methods

Umbul-Telomoyo is located in the Quarter of Telomoyo Mount, Central Java. The geothermal system in this region is formed by the residual heat coming from the magma chamber with associated with recent activity of Telomoyo Mount complex. The estimation of geothermal reserve is approximately 92 MWe which was feasible to further development. The surface manifestations consisting of the Candi Umbul hot spring (APCU), Pakis Dadu hot spring (APPD) and Candi Dukuh hot spring (APPD). Based on Cl-SO4-HCO3 diagram, it shows that APCDbelongs to chloride-bicarbonate water, while APCU and APPD belongs to chloride water. All hot springs included to the immature water zone according to the Na-K-Mg diagram. The Cl-Li-B diagram described that this geothermal system consists of two different reservoirs in which this data was also supported by Magnetotellurik survey (MT). Temperature estimation of reservoir of Candi Dukuh is around 215-230°C and reservoir of Candi Umbul is around 235-250°C. Litology in CTL-1 and CTL-2 wells were generally dominated by products of Telomoyo volcanic, lava and pyroclastic rocks. Litology found in CTL-1 and CTL-2 wells has changed to range of intensity low and high. Minerals formed in CTL-1 and CTL-2 wells were generally clay minerals (smectite, kaolinite, chlorite, and illite), calcite, secondary quartz, anhydrite, and epidote, gypsum, siderite, hematite, zeolite and alunite, that altered primary minerals. This alteration rocks turned into a caprock in the Umbul-Telomoyo geothermal system.