The issue of drilling horizontal wells in excessively hot zones has been gaining attention with the recent related advancements. Operation of the closed U-tube system also considered for energy extraction from such hot zones involves circulation in the joined horizontal wells without any contact of the circulating fluid with the surrounding formation. The disconnection in question ensures stable and unproblematic operation. In this study, a numerical solution with automatic time step adjustment property was arranged to figure out the temperature distribution in the considered closed U-tube system. The numerical solution was validated with the analytical solution utilized for estimation of the temperature of the circulating mud at different well depths during drilling. Simulation runs revealed excessive computational effort associated to unproper determination of the automatic time step adjustment parameters. Thereby, increment and reduction factors for the time step adjustment were modified continuously during the computation process by means of an optimization algorithm in contrary to the traditional approach in which these parameters are kept constant. It was observed that the solution with the fixed increment and reduction factors was inefficient in terms of the computation effort for the considered closed U-tube system. By means of the proposed solution involving the perpetual improvement of these factors, the computation effort and time was significantly improved and the accuracy was preserved despite the greater time steps.
Anahtar Kelimeler: Closed U-tube Systems, Heat transfer, Automatic Time Step Adjustment, Optimization, Simulation Run, Geothermal, Reservoir Engineering