| Keywords |
Bula Basin, Maluku, Indonesia, Hotspring, Niff, Bula, Seram, geothermal, geothermal fluids, oil filed |
| Abstract |
An early interpretation on surface geothermal features characteristic, especially in chemistry characteristic fluids is necessary as the door for the next step research of the geothermal system. The inventory was conducted in 2018 and the methods are inventory of surface geothermal features, sampling the waters of them, classifying the type of geothermal manifestation, and interpreting for thermal water analysis for the type of the water and consideration the temperature reservoir through the water geothermometers. Bula Basin is a non-volcanic area, located at East Seram Regency, Maluku, Seram Island, Indonesia. Generally, it is included in the Outer Banda non-volcanic arc which consist of metamorphic rocks in the Permian-Triassic. The geothermal manifestation was inventoried in 2018, at Bula basin, near the oil field, and only warm springs (Nif-1 and Nif-2) and light alteration were found. The Nif warm springs are in the Bula basin and is based on the regional geological map of the Bula, Watubela and Maluku sheets. The Nif warm springs are located in the Salas Complex rock, which consists of various exotic boulders with a clay matrix, aged Mio-Pliocene. It is located at Dawang village, Teluk Waru district, East Seram regency, and the coordinates are 669877 mE, 9639782 mS, with an elevation of 83 asl. The only geothermal manifestations are two clusters warm springs, i.e.: Nif-1 and Nif-2 warm springs with temperatures of about 44.9-49.1oC, neutral pH, the electrical conductivity of about 4,810-5,380 µS/cm, and the flow rate of 0.1-3 l/s. The warm springs are manifested at limestone lithology; clear, sulphur odour, and oily smell because of oil seepage near the warm springs. The Nif warm springs are plotted in the middle of the Cl-SO4-HCO3 diagram; chloride-bicarbonate and sulphate-chloride water type based on the Cl-SO4-HCO3 diagram and mostly plotted in a partial equilibrium zone based on the relative Na-K-Mg diagram. The temperature of the reservoir is medium at about 155oC from Na-K Giggenbach geothermometer. The type of Nif-Bula geothermal system could be a fractured system or a heat sweep system, and this still needs additional geophysical data. The Indonesian government is focusing on the development of Eastern Indonesia. The early interpretation characteristic of geothermal chemistry fluids of Nif warm springs in Bula Basin would be a useful consideration for the next step investigation using more completed methods to understand the Nif-Bula geothermal system. |