Geothermics and Geothermal Energy pp 297-308 | Cite as
Reservoir Lifetime and Heat Recovery Factor in Geothermal Aquifers used for Urban Heating
Abstract
Simple models are discussed to evaluate reservoir lifetime and heat recovery factor in geothermal aquifers used for urban heating. By comparing various single well and doublet production schemes, it is shown that reinjection of heat depleted water greatly enhances heat recovery and reservoir lifetime, and can be optimized for maximum heat production. It is concluded that geothermal aquifer production should be unitized, as is already done in oil and gas reservoirs.
Key words
Reservoir lifetime Heat recovery factor Doublet Geothermal aquifer ReinjectionNomenclature
- a
distance between doublets in multi-doublet patterns, meters
- A
area of aquifer at base temperature, m2 drainage area of individual doublets in multi-doublet patterns, m2
- D
distance between doublet wells, meters
- h
aquifer thickness, meters
- H
water head, meters
- Q
production rate, m3/sec.
- re
aquifer radius, meters
- rw
well radius, meters
- Rg
heat recovery factor, fraction
- s
water level drawdown, meters
- ∆t
producing time, sec.
- T
aquifer transmissivity, m2/sec.
- v
stream-channel water velocity, m/sec.
- ∆θ
actual temperature change, °C
- ∆θ′
theoretical temperature change, °C
- θ
water temperature, °C
- λ
heat conductivity, W/m/°C
- λr
rock heat conductivity, W/m/°C
- ρaca
aquifer heat capacity, J/m3/°C
- ρacr
rock heat capacity, J/m3/°C
- ρwcw
water heat capacity, J/m3/°C
- ϕ
aquifer porosity, fraction
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