Various - rock on: hot in the city 1982


The findings, recently published in the journal Geology , suggest that New England may not be so immune to abrupt geological change.

Notwithstanding their lack of fluids to transfer heat toward the surface, thermal anomalies in such intrusions do constitute significant thermal resources, if they are shallow enough to be reached by drilling. Hot dry rock (HDR) systems require such rocks to be artificially fractured at depth so that water can be pumped into them, heated above boiling temperature and then returned to the surface to flash to steam in an electricity generating plant. Figure 6 shows in schematic form how hot, dry rock can become a high enthalpy geothermal resource. A well that penetrates the intrusion is used to inject water at very high pressures into zones of natural fracturing in the rock. Water injected through the well not only heats up but enhances any fractures and creates more, by a process of hydrofracturing . This creates paths along which water can move, effectively creating an artificial heat exchange zone that feeds superheated water to another well that takes it back to the surface. The practical difficulties of extracting heat from such deep rocks can be formidable. Drilling through crystalline rocks is far more costly than through sedimentary strata. For an HDR field to be viable, water has to circulate through large volumes of hydrofractured rock. The HDR approach is being pursued because of its potential in areas well away from active plate margins. Steam generation that cools 1 km 3 of a fractured hot dry rock by only 1 °C will provide the same amount of energy as 7 × 10 4 t of coal.


Various - Rock On: Hot In The City 1982Various - Rock On: Hot In The City 1982Various - Rock On: Hot In The City 1982Various - Rock On: Hot In The City 1982

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