Applications of Non-Isothermal Lumped-Parameter Models; Case Studies of Turkey’s İzmir Balçova-Narlıdere and Afyon Ömer-Gecek Fields

Abstract

Unlike the existing isothermal lumped-parameter models in the literature, non-isothermal models couple both heat and mass balance equations to account for temperature changes in addition to pressure changes. These changes result from production of hot water, re-injection of low-temperature water, and natural recharge of water (possibly with a temperature different than that of the reservoir). In this study, applications of an in-house non-isothermal lumped-parameter model to pressure and temperature measurements from Turkey’s İzmir Balçova-Narlıdere and Afyon Ömer-Gecek are presented. The model developed can be used for performing history-matching and predicting both pressure and temperature behaviors of low temperature geothermal reservoirs containing single-phase liquid water are presented. Such a model helps to estimate reservoir bulk volume, porosity, temperature of the recharge source, recharge index, initial reservoir pressure and temperature by history matching measured reservoir pressure and temperature data by minimization of a weighted least-squares objective function. By using history matched models based on the non-isothermal model, as demonstrated for the case of İzmir Balçova-Narlıdere geothermal field, future reservoir temperature behavior which cannot be predicted by a lumped-parameter model assuming isothermal flow can be predicted under various production/injection scenarios. However, as shown in the Afyon Ömer-Gecek field example case, if the temperature and pressure data recorded at an observation well are not representative of the average pressure and temperature of the reservoir for which the non-isothermal model is built on, then matching such pressure and/or temperature may lead to inconsistent parameter estimates, and hence for such data cases, a non-isothermal model should be used and interpreted with caution.