| Abstract |
This paper describes a lesson learned on applying United Nations Framework Classification for Resources (UNFC-2009) to Geothermal Energy Reources in Mataloko Geothermal Field, Flores Island, Indonesia. UNFC-2009 is a generic principle-based system in which quantities are classified by three fundamental criteria, which are combined in a three-dimensional system. Those criteria are (1) Geology knowledge, (2) Project feasibility and (3) Socio-economic viability. They are known as G, F and E criteria respectively. Mataloko is a Brownfield Project where existing plant has been constructed to produce 2.5MWe from two production wells. Those are MT-3 and MT-5 wells which were drilled up to 613.0m and 378.2m respectively. The plant was in operation only few months due to turbine wear and low pressure steam supply issues. PLN, the State Owned Enterprise, as the current owner of the field, plan to add the production for 2x10 Mwe and to recommission the existing 2.5 MWe plant. The Project Lifetime is limited by a Ministry of Energy & Mineral Resources Decree which assigns Mataloko Geothermal Working Area licence to PLN until 28 December 2050. So the Project is expected to generate 2.5 MWe for 3 years (2020, 2021 and 2022) and 22.5 MWe for 28 years (2023 to 2050, inclusive), with average plant load factor of 92%. Thus, it is proposed to drill 7 production wells at the indicative deeper reservoir from exploration development program. The well targeting is based on the previous data carried out by Geological Agency, consisting of exploration and shallow gradient wells (MT-1, MT-2, MT-4, and MT-6), geophysical data that include MT, DC-resistivity of Schlumberger array and gravity, surface and sub-surface geology and intensive surface geochemistry data. The exploration data suggest apparent equilibrium temperatures of at least 290-300°C are indicated for the steam discharged by the Mataloko geothermal wells and Mataloko fumaroles. However, the existence and characteristics of the inferred water-dominated deep reservoir need to be proved and evaluated by drilling exploratory wells. Furthermore, the conduction of an appropriate logging and testing program is essential. Additional 3G field data acquisition to confirm reservoir dimensions, physical characteristics and properties are also proposed. Based on the above data, we may conclude that geothermal resource potential in Mataloko has greater capacity although additional exploration and drilling is required. However, Flores island has modest demand and modest growth of demand, so the proposed development only utilizes a small portion of the possible subsurface resource. In applying the UNFC classifications, for the project describe above, several problems have been encounter and discussed as mentioned below: 1. The discussion reveals different interpretations of the UNFC texts by different members of the group even among the expert, thus the expert group proposed some modification in terminology of UNFC or suggestion to add footnote on the report to help the reader. 2. There are different interpretation and perspective about evidences sufficiency to infer the level of uncertainty from the same data. 3. The background of understanding from the people who wrote the report, hence Indonesian geothermal community, previously have its own classification that make it difficult to adopt the concept of UNFC. Thus the classification often falls at wrong or arguable axis. A training on this classification is necessary for better understanding. |