Sunday, July 20, 2008

Lesugolo Geothermal Prospect Area

Lesugolo geothermal prospect area is located 5 km southern part of Mboto village. It is administratively in the districts of Maurole and Kotabaru, Ende regency, East Nusa Tenggara province. The study area covers an area of about 144 km2 (12 x 12 km2) which is bounded by the following longitudes and latitudes : 121°50'30" - 121°56'30" E and 08°32'00" - 08°38'00" S.
Stratigraphically, it comprises of two main rocks, i.e., quartemary volcanic rocks located unconformity on the neritic fasies volcanoclastic sedimentary rocks of tertiary age. The geological structure represents the lineament which are interpreted as a fault directed to northeast-southwest, northwest-southeast and west-east. The appearance of the geothermal discharges consists of hot spring of Lesugolo and Ae Dhara and warn spring of Lowo Geru dan Ae Petu with the presence of travertine sinter.
The interpretation of resistivity data combined with the interpretation of geological and geochemical data has proved to be able to delineate the prospect area of Lesugolo geothermal field and its vicinity more clearly. The prospect area is located in the northwest of the southeast side of Gunung Keli Watuapi, with an area of about 6,2 km2. Hot water system reservoir lies at an average depth under 500 m with a temperature of about 160-190°C. The rocks of the reservoir and caprock is on bedrock made of tertiary volcanoclastic sedimentary rocks in the form of tuffs and tuff breccias. The rain catching area is around Gunung Keli Watuapi with the outflow runs moving up to southeastward of the hot spring of Lesugolo. The presents of the three paths of fault in the study area is expected to be the permeability area that has the very potential of trapping system of Lesugolo geothermal.
The results of geothermal potential calculation recognized the prospect area with potential up to 50 MWe. The geothermal area of Lesugolo has a significant prospect necessary to develop both for the purpuse of indirect use as a small-scale geothermal power plant and various direct used of it.

Saturday, July 19, 2008

Sokoria Geothermal Prospect Area

Sokoria Geothermal Field is situated about 37 km northeastern part of Ende city, belong to the administrative region of Sokoria village, district of East Ndona, Ende regency, East Nusa Tenggara. The thermal gradient well of the Sokoria geothermal field consists of 2 wells, those are SK-1 and SK-2. Geographically, SK-1 and SK-2 are respectively located at 121° 45’ 58” East - 08° 47’ 25” South and 121° 45’ 59” East - 08° 47’ 10” South.
Rock unit of SK-1 from top to bottom consists of Top Soil, Tuff Breccia, Andesite, Altered Andesite, Altered Andesite Breccia and Altered Andesite Basaltic, whereas SK-2 composes of Altered Andesite, Altered Andesite Breccia and Altered Andesite Basaltic. An interbedding occurred among Altered Andesite, Altered Andesite Breccia and Altered Andesite Basaltic characterize the rock originating from several times of eruption periods of the Mutubasa Volcano in the Mutubasa’s old caldera.
The entirely rock have undergone a hydrothermal alteration with a varied alteration intensity from weak to intense (SM/TM = 10-85%). The hydrothermal alteration is generally characterized by processes of argilitization, oxidation with/without piritization, silicification, carbonatization, anhydritization and chloritization. The type of alteration is included into “Argillic” functioning as caprock in the geothermal field of Sokoria. The environment setting of alteration mineral indicates a netral to acid fluid condition characterizing its formation on a high-temperature of hot water and vapour system.
From the result of temperature logging measurement it has been obtained an anomaly of average temperature at SK-1 by 13 times normal thermal gradient, that is about 40 deg C/100 m, whereas SK-2 has an anomaly of average temperature by 12,6 times normal thermal gradient, that is about 37,8 deg C/100 m. Based on the result of geological analysis and temperature logging measurement show subsurface heat flow at the field of Sokoria and it has a prospect to be developed further.