How deep do you have to drill to obtain a sustained temp. of 15c when drilling for geo thermal heating?

Question

central alberta

Answer 1

It varies a lot depending on location. I doubt you'll find an accurate number unless you can find someone who has drilled in your area.

http://www.enotes.com/earth-science/geot...

The geothermal gradient is the rate of change of temperature (ΔT) with depth (ΔZ), in the earth. Units of measurement are °F/100 ft or °C/km. In the geosciences, the measurement of T is strongly associated with heat flow, Q, by the simple relation: Q=KΔT/ΔZ, where K is the thermal conductivity of the rock.

Temperatures at the surface of the earth are controlled by the Sun and the atmosphere, except for areas such as hot springs and lava flows. From shallow depths to about 200 ft (61 m) below the surface, the temperature is constant at about 55°F (11°C). In a zone between the near surface and about 400 ft (122 m), the gradient is variable because it is affected by atmospheric changes and circulating ground water. Below that zone, temperature almost always increases with depth. However, the rate of increase with depth (geothermal gradient) varies considerably with both tectonic setting and the thermal properties of the rock.

High gradients (up to 11°F/100 ft, or 200°C/km) are observed along the oceanic spreading centers (for example, the Mid-Atlantic Rift) and along island arcs (for example, the Aleutian chain). The high rates are due to molten volcanic rock (magma) rising to the surface. Low gradients are observed in tectonic subduction zones because of thrusting of cold, water-filled sediments beneath an existing crust. The tectonically stable shield areas and sedimentary basins have average gradients that typically vary from 0.82–1.65°F/100 ft (15–30°C/km).

The geothermal gradient is important for the oil, gas, and geothermal energy industries. Downhole logging tools must be hardened if they are to function in deep oil and gas wells in areas of high gradient. Calculation of geothermal gradients in the geological past is a critical part of modeling the generation of hydrocarbons in sedimentary basins.

try

http://www.geothermalheatingreport.com/g...

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