Method and apparatus for determining vertical heat flux of geothermal field
- LaJolla, CA
A method and apparatus for determining vertical heat flux of a geothermal field, and mapping the entire field, is based upon an elongated heat-flux transducer (10) comprised of a length of tubing (12) of relatively low thermal conductivity with a thermopile (20) inside for measuring the thermal gradient between the ends of the transducer after it has been positioned in a borehole for a period sufficient for the tube to reach thermal equilibrium. The transducer is thermally coupled to the surrounding earth by a fluid annulus, preferably water or mud. A second transducer comprised of a length of tubing of relatively high thermal conductivity is used for a second thermal gradient measurement. The ratio of the first measurement to the second is then used to determine the earth's thermal conductivity, k.sub..infin., from a precalculated graph, and using the value of thermal conductivity thus determined, then determining the vertical earth temperature gradient, b, from predetermined steady state heat balance equations which relate the undisturbed vertical earth temperature distributions at some distance from the borehole and earth thermal conductivity to the temperature gradients in the transducers and their thermal conductivity. The product of the earth's thermal conductivity, k.sub..infin., and the earth's undisturbed vertical temperature gradient, b, then determines the earth's vertical heat flux. The process can be repeated many times for boreholes of a geothermal field to map vertical heat flux.
- DOE Contract Number:
- E(04-3)-1318
- Assignee:
- United States of America as represented by United States (Washington, DC)
- Patent Number(s):
- US 4313342
- OSTI ID:
- 864118
- Country of Publication:
- United States
- Language:
- English
Similar Records
Method and apparatus for determining vertical heat flux of geothermal field
Method for determining thermal conductivity and thermal capacity per unit volume of earth in situ
Related Subjects
apparatus
determining
vertical
heat
flux
geothermal
field
mapping
entire
based
elongated
heat-flux
transducer
10
comprised
length
tubing
12
relatively
thermal
conductivity
thermopile
20
inside
measuring
gradient
positioned
borehole
period
sufficient
tube
reach
equilibrium
thermally
coupled
surrounding
earth
fluid
annulus
preferably
water
mud
measurement
ratio
determine
infin
precalculated
graph
value
determined
temperature
predetermined
steady
balance
equations
relate
undisturbed
distributions
distance
gradients
transducers
product
determines
process
repeated
times
boreholes
map
vertical heat
thermal gradient
surrounding earth
period sufficient
heat flux
temperature gradient
thermal conductivity
temperature gradients
temperature distribution
thermally coupled
thermal equilibrium
vertical temperature
preferably water
heat balance
geothermal field
determining vertical
/374/73/