Fréttir


Meistaravörn Jaime Jemuel C. Austria, Jr. fyrir M.S. gráðu í vélaverkfræði

28.5.2008

Meistaravörn Jaime Jemuel C. Austria, Jr. fyrir M.S. gráðu í vélaverkfræði frá Háskóla Íslands verður í dag, 28. maí kl. 13:00-14:00 í VR-II, stofu 157. Við hvetjum alla til þess að mæta!

Production Capacity Assessment of the Bacon-Manito Geothermal System, Philippines

A sustainable production capacity of the Bacon-Manito geothermal system (BacMan) is assessed in this study by three models of different complexity. A base case of 150 MW electrical generation is considered and production is constant up to year 2031. The numerical models considered are based on volumetric, lumped-parameter and a full scale, 3D well-by-well methods. A conceptual reservoir model is first proposed based on previous geoscientific research and downhole data. The geothermal reservoir has an estimated area of 18 km2, its thickness exceeds 1500 m and temperatures range 240-320 °C. A volumetric model, using Monte Carlo style simulation, indicates that a production capacity of 200 MWe can be maintained for another 25 years with 90% probability. The lumped model predicts annual pressure drawdown of 0.67 bars, resulting in a manageable total drawdown of 25 bars in year 2031. For the well-by-well method, a distributed parameter numerical model was developed using the simulator iTOUGH2. The simulator minimizes misfit between observed and simulated response by inverting for a set of 15 model parameters. These include mass and enthalpy of hot and deep recharge and 12 permeabilities. A “best” model resulted in far-field permeability of 0.5 to 5 milli-Darcies while the productive wellfield ranges from 25 to 100 mD. The deep recharge was calibrated as 98 kg/s of 1830 kJ/kg enthalpy. Sensitivity analyses show that the model is most sensitive to pressure drawdown data followed by enthalpy of flowing wells. The model predicts that at least five more production and three reinjection wells are needed for future high-pressure steam requirement of the 150 MW power plant. Stable enthalpies of production wells are predicted for the 23 years studied, indicating that reservoir temperature drawdown will be moderate. Reservoir boiling will, however, be intensive and change pressure gradients from hydrostatic to vapour static in the centre field. Instead of predicting reservoir performance for tens or hundreds of year, it was decided to stop production in year 2031 and monitor recovery of heat and mass reserves. Both the lumped and the detailed numerical models predict full pressure recovery in a century while the heat reserve needs considerably longer time. A sustainable production criterion seems therefore achieved by resting the reservoir 3 years for each year it produces. New technologies should change this estimate.

Committee in charge:
Mr. Grimur Björnsson
Mr. Jónas Ketilsson
Dr. Pall Valdimarsson

Moderator:
Dr. Gudni Axelsson