Effect of heat transfer on the performance of geothermal wells

Abstract

The effect of heat losses on the performance of geothermal wells is investigated by means of a one-dimensional mathematical model, which includes some novel features for the calculation of the pressure drop along the well. One of two existing correlations is selected for the friction gradient in the slug-flow regime according to the value of a new dimensionless parameter. In addition, a modified version of Tachimori's correlation is used for the mist-flow regime. The model also accounts for the effect of transient heat transfer between the well and the surroundings by accommodating temporal variations of the temperature distribution within the surrounding rock. The capability of the model is assessed by comparing the calculated results with existing sets of experimental data. The model predictions are in good agreement with the data. It is found that heat transfer effects are particularly significant when the well is running outside the range of nominal operating conditions, e.g. when the well is throttled. Comparison of the model predictions with those obtained applying Ramey's method, shows the advantages of using the present approach under particular circumstances.