Numerical Modeling of the Balcova-Narlidere Geothermal Field, Turkey

Abstract

The Balcova-Narlidere geothermal field, located in the Izmir bay of the Aegean Coast of Turkey is a liquid-dominated system with a maximum temperature of 140 C. The geothermal water has been characterized as "fresh" underground water and used for heating of Balcova-Narlidere district. The geothermal water has been produced/reinjected through a total of 21 wells: 9 deep wells with depths ranging from 564 m to 1100 m, and 12 shallow wells with depths ranging from 48.5 m to 160 m. The net fluid production per year from the field was around 650,000 m3, when this study was conducted.
A three-dimensional numerical simulation model of the field was developed using the simulation code TOUGH2. The numerical model was based on a conceptual model derived from geological, geophysical, geochemical data as well as data from drilling and well tests. Natural state modeling was conducted by matching the temperature and pressure data initially measured at the wells. The natural state modeling provided satisfactory matches of measured temperature data of all the wells and represented the major qualitative features of the field, that resulted in a net recharge mass rate of about 51 kg/s and a net heat recharge of about 33 MWt.
The natural state model was further calibrated to match all available production and injection data (flow rates, pressures and temperatures vs. time) of the wells. After calibrating the model to all available data, the model was then used to predict overall reservoir performance and individual well performances under existing and proposed production/injection schedules for the next 20 years. Forecasting runs showed that production could be sustained for the next 20 years in terms of bottomhole pressures and temperatures. Forecasting runs considering only deep well production and injection indicated that the reservoir could be better sustained in terms of bottomhole pressures and temperatures for the next 20 years. In addition, forecasting runs assuming two new wells drilled in the field, with injectivities similar to currently available deep wells, and 20% increase in net production rate showed that the system could also be sustained for the next 20 years.