Limits of Heat Extraction from Dry Hole

Abstract

Deep borehole heat exchangers are an environmentally favorable way for geothermal energy production. The weakness of this proposed production technology is the moderate temperature of the outflowing water and the relatively low thermal power. The impact of the bottom-hole depth and the heat conductivity of the surrounding rock are also considered.

The primary limit of the extractable thermal power is the restricted heat replenishment by conduction towards the well. In order to the temperature difference is negligible, between the tubing and the annulus heat insulation is necessary. During the initial period of the operation the temperature and the power has a higher value, but they tend a lower equilibrium value. This is the sustainable production of the system. Seminumerical simulation is used to determine this limit. Electricity production from dry holes cannot be an economic way.

But the direct heat utilization would be possible in confirmation with a heat pump.