Advective (heat sweep) geothermal systems

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Conference Proceedings: Advective (heat sweep) geothermal systems

Advective (heat sweep) geothermal systems occur in tectonically active regions with moderate to mountainous terrain and favourable hydrological settings that induce „forced convection‟. All advective systems are associated with deep infiltration and deep secular flow paths transferring some heat from the thermal regime in the upper crust to small discharge centres at the surface in a hydrological sink setting (artesian basins, for example). Conceptual models of eight different geothermal advective flow systems are presented. Their natural heat discharge is low (1 to 10 MW) and the subsurface area affected by heat sweeps is of the order of c. 200 to c. 2,000 km2. High reservoir temperatures (T > 150 deg C) had been previously predicted for all prospects, assuming that constituents of discharged thermal waters reflect deep fluid-rock equilibration and that deep equilibrium temperatures can be predicted from the unchecked application of cation-based Na-K-Ca geo-thermometers. This study shows that in half of the prospects fully equilibrated fluids do not discharge although minimum deep fluid temperatures can be estimated by using SiO2 and K-Mg geothermometers. The search for deep reservoirs has led to the drilling of many unsuccessful wells which in three prospects reached depths between 1 and 2 km with temperatures between 70 and 125 deg C at 1 km depth. Direct use appears to be the best utilization mode for exploiting these resources; the success of producing electricity (binary plants) has been limited since plants have failed at two out of three sites.

M. P. Hocstein, K. Zheng, S. Pasvanoglu and P. Vivian-Neal

38th Workshop on Geothermal Reservoir Engineering; Stanford University; 2013/02/11

Stanford University, 2013

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M. P. Hocstein, K. Zheng, S. Pasvanoglu, P. Vivian-Neal. 2013. Advective (heat sweep) geothermal systems. Proceedings of 38th Workshop on Geothermal Reservoir Engineering; Stanford, California: Stanford University.